Physical and Numerical Modeling of SAGD Under New Well ...
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2013-09-23
Physical and Numerical Modeling of SAGD Under New
Well Configurations
Tavallali Mohammad
Tavallali M (2013) Physical and Numerical Modeling of SAGD Under New Well Configurations
(Unpublished doctoral thesis) University of Calgary Calgary AB doi1011575PRISM27348
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doctoral thesis
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UNIVERSITY OF CALGARY
Physical and Numerical Modeling of SAGD Under New Well Configurations
by
Mohammad Tavallali
A THESIS
SUBMITTED TO THE FACULTY OF GRADUATE STUDIES
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
DEPARTMENT OF CHEMICAL amp PETROLEUM ENGINEERING
CALGARY ALBERTA
SEPTEMBER 2013
copy Mohammad Tavallali 2013
ii
ABSTRACT
This research was aimed at investigating the effect of well configuration on SAGD
performance and developing a methodology for optimizing the well configurations for
different reservoir characteristics The role of well configuration in determining the
performance of SAGD operations was investigated with help of numerical and physical
models
Since mid 1980rsquos SAGD process feasibility has been field tested in many successful
pilots and subsequently through several commercial projects in various bitumen and
heavy oil reservoirs Although SAGD has been demonstrated to be technically successful
and economically viable it still remains very energy intensive extremely sensitive to
geological and operational conditions and an expensive oil recovery mechanism Well
configuration is one of the major factors which affects SAGD performance and requires
greater consideration for process optimization
Several well patterns were numerically examined for Athabasca Cold Lake and
Lloydminster type of reservoirs Numerical modeling was carried out using a commercial
fully implicit thermal reservoir simulator Computer Modeling Group (CMG) STARS
For each reservoir one or two promising well patterns were selected for further
evaluations in the 3-D physical model or future field pilots
Three well patterns including the Classic SAGD pattern Reverse Horizontal Injector
and Inclined Injector of which the last two emerged as most promising in the numerical
study were examined in a 3-D physical model for Athabasca and Cold Lake reservoirs
The physical model used in this study was a rectangular model that was designed based
on the available dimensional analysis for a SAGD type of recovery mechanism Two
types of bitumen representing the Athabasca and Cold Lake reservoirs were used in the
experiments A total of seven physical model experiments were conducted four of which
used the classic two parallel horizontal wells configuration which were considered the
base case tests Two experiments used the Reverse Horizontal Injector pattern and the last
experiment tested the Inclined Injector pattern The suggested well patterns provided
operational and economical enhancement to the SAGD process over the standard well
iii
configuration and this research strongly suggests that both of them should be examined
through field pilots in AthabascaCold Lake type of reservoirs
In order to develop further insight into the performance of different well patterns the
production profile of each experiment was history matched using CMG-STARS Only the
relative permeability curves porosity permeability and the production constraint were
changed to get the best match of the experimental results Although it was possible to
history match the production performance of these tests by changing the relative
permeability curves the need for considerable changes in relative permeability shows
that the numerical model was not able capture the true hydrodynamic behavior of the
modified well configurations
iv
ACKNOWLEDGEMENTS
It would not have been possible to complete this doctoral thesis without the help and
support of the kind people around me to only some of whom it is possible to give
particular mention here
First and foremost I wish to express my sincere gratitude to Dr Brij B Maini and Dr
Thomas G Harding for their generous guidance encouragement and support throughout
the course of this study This thesis would not have been possible without their
unsurpassed knowledge and patience I really feel privileged to have Dr Maini as my
supervisor and Dr Harding as my Co-Supervisor during these years of study
I would like to extend my thanks to Mr Paul Stanislav for his helpful technical support
during performing the experiments
I owe my respectful gratitude to the official reviewers of this thesis Dr SA Mehta Dr
M Dong Dr G Achari and Dr K Asghari for their critically constructive comments
which saved me from many errors and definitely helped to improve the final manuscript
I would like to acknowledge all the administrative support of the Department of
Chemical and Petroleum Engineering during this research
Irsquom practically grateful for the support of Computer Modeling Group for providing
unlimited CMGrsquos license and for their technical support
I must express my gratitude to Narges Bagheri my best friend for her continued support
and encouragement during all of the ups and downs of my research
I would like to thank my friends Bashir Busahmin Cheewee Sia Farshid Shayganpour
and Rohollah Hashemi for their support during my research
Finally I wish to thank my dear parents for their patient love and permanent moral
support
v
DEDICATION
To my parents my sisters Marjan Mozhgan and
Mozhdeh and my best friend Narges
vi
TABLE OF CONTENTS
ABSTRACT ii ACKNOWLEDGEMENTS iv DEDICATIONSv TABLE OF CONTENTS vi LIST OF TABLESx LIST OF FIGURES xi LIST OF SYMBOLES ABBREVIATIONS AND NUMENCLATURES xx
CHAPTER 1 INTRODUCTION1 11 Background 2 12 Dimensional Analysis9 13 Factors Affecting SAGD Performance10
131 Reservoir Properties 10 1311 Reservoir Depth 10 1312 Pay Thickness Oil Saturation Grain Size and Porosity11 1313 Permeability (kv kh)11 1314 Bitumen viscosity11 1315 Heterogeneity11 1316 Wettability12 1317 Water Leg13 1318 Gas Cap13
132 Well Design13 1321 Completion13 1322 Well Configuration 14 1323 Well Pair Spacing 14 1324 Horizontal Well Length 14
133 Operational Parameters 14 1331 Pressure 14 1332 Temperature 15 1333 Pressure Difference between Injector and Producer15 1334 Subcool (Steam-trap control)15 1335 Steam Additives 16 1336 Non-Condensable Gas 16 1336 Wind Down16
14 Objectives17 14 Dissertation Structure 19
CHAPTER 2 LITERATURE REVIEW21 21 General Review 22 22 Athabasca 33 23 Cold Lake 35 24 Lloydminster 36
vii
CHAPTER 3 GEOLOGICAL DESCRIPTION 39 31 Introduction 40 32 Athabasca 41 33 Cold Lake 47 34 Lloydminster 53 35 Heterogeneity 59
CHAPTER 4 EXPERIMENTAL EQUIPMENT AND PROCEDURE62 41 Equipmental Apparatus 63
411 3-D Physical Model63 412 Steam Generator 67 413 Temperature Probes68
42 Data Acquisition68 43 RockFluid Property Measurements 68
431 Permeability Measurement Apparatus 68 432 HAAKE Roto Viscometer69 433 Dean Stark Distillation Apparatus71
44 Experimental Procedure 73 441 Model Preparation 73 442 SAGD Experiment 75 443 Analysing Samples 77 444 Cleaning78
CHAPTER 5 NUMERICAL RESERVOIR SIMULATION 79 51 Athabasca 80
511 Reservoir Model 80 512 Fluid Properties 82 513 Rock-Fluid Properties83 514 Initial CondistionGeomechanics 85 515 Wellbore Model85 516 Wellbore Constraint 86 517 Operating Period87 518 Well Configurations 87
5181 Base Case 88 5182 Vertical Inter-well Distance Optimization94 5183 Vertical Injector 98 5184 Reversed Horizontal Injector 101 5185 Inclined Injector Optimization104 5186 Parallel Inclined Injector108 5187 Multi-Lateral Producer111
52 Cold Lake 113 521 Reservoir Model 113 522 Fluid Properties 114 523 Rock-Fluid Properties115
viii
524 Initial CondistionGeomechanics 116 525 Wellbore Model116 526 Wellbore Constraint 116 527 Operating Period116 528 Well Configurations 117
5281 Base Case 117 5282 Vertical Inter-well Distance Optimization121 5283 Offset Horizontal Injector 123 5284 Vertical Injector 126 5285 Reversed Horizontal Injector 129 5286 Parallel Inclined Injector132 5287 Parallel Reversed Upward Injectors135 5288 Multi-Lateral Producer137 5289 C-SAGD140
53 Lloydminster 144 531 Reservoir Model 146 532 Fluid Properties 147 533 Initial CondistionGeomechanics 148 534 Wellbore Constraint 148 535 Operating Period149 536 Well Configurations 149
5361 Offset Producer 151 5362 Vertical Injector 154 5363 C-SAGD157 5364 ZIGZAG Producer 160 5365 Multi-Lateral Producer162
CHAPTER 6 EXPERIMENTAL RESULTS AND DISCUSSIONS166 61 Fluid and Rock Properties 168 62 First Second and Third Experiments 171
621 Production Results171 622 Temperature Profiles 177 623 History Matching the Production Profile with CMGSTARS183
63 Fourth Experiment187 631 Production Results187 632 Temperature Profiles 188 633 History Matching the Production Profile with CMGSTARS196
64 Fifth Experiment200 641 Production Results200 642 Temperature Profiles 201 643 Residual Oil Saturation 209 644 History Matching the Production Profile with CMGSTARS211
65 Sixth Experiment 215 651 Production Results215 652 Temperature Profiles 219
ix
653 Residual Oil Saturation 224 654 History Matching the Production Profile with CMGSTARS226
66 Seventh Experiment 230 661 Production Results230 662 Temperature Profiles 234 663 Residual Oil Saturation 240 664 History Matching the Production Profile with CMGSTARS241
CHAPTER 7 CONCLUSIONS AND RECOMMENDATIONS246 71 Conclusions 247 72 Recommendations 250
REFERENCES 252
x
LIST OF TABLES
Table 1-1 Effective parameters in Scaling Analysis of SAGD process10
Table 4-1 Dimensional analysis parameters field vs physical64
Table 4-2 Cylinder Sensor System in HAAKE viscometer70
Table 5-1 Reservoir properties of model representing Athabasca reservoir82
Table 5-2 Fluid roperties representing Athabasca Bitumen 82
Table 5-3 Rock-Fluid properties85
Table 5-4 Analaytical solution paramters 93
Table 5-5 Inclined Injector case104
Table 5-6 Reservoir and fluid properties for Cold Lake reservoir model115
Table 5-7 Values of dilation-compaction properties for Cold Lake reservoir model141
Table 5-8 Reservoir and fluid properties for Lloydminster reservoir model148
Table 6-1 Summary of the physical model experiments 168
Table 6-2 Summary watergasoil relative permeability end points of 5th 6th and 7th
experiments 241
xi
LIST OF FIGURES
Figure 1-1 μ minusT relationship 2
Figure 1-2 Schematic of SAGD3
Figure 1-3 Vertical cross section of drainage interface 5
Figure 1-4 Steam chamber interface positions 7
Figure 1-5 Interface Curve with TANDRAIN Theory 8
Figure 1-6 Various well configurations19
Figure 2-1 Chung and Butler Well Schemes26
Figure 2-2A Well Placement Schematic by Chan 27
Figure 2-2B Joshirsquos well pattern27
Figure 2-3 Nasrrsquos Proposed Well Patterns28
Figure 2-4 SW-SAGD well configuration 29
Figure 2-5 SAGD and FAST-SAGD well configuration29
Figure 2-6 Well Pattern Schematic by Ehlig-Economides 30
Figure 2-7 The Cross-SAGD (XSAGD) Pattern 30
Figure 2-8 The JAGD Pattern 31
Figure 2-9 U-Shaped horizontal wells pattern32
Figure 2-10 The Schematic of well patterns proposed by Bashbush and Pina 32
Figure 2-11 Athabasca Oil Sandrsquos Projects 33
Figure 3-1 Albertarsquos bitumen resources estimate volume as of December 31 201140
Figure 3-2 Bitumen and Heavy Oil deposit of Canada 41
Figure 3-3 Distribution of pay zone on eastern margin of Athabasca42
Figure 3-4 Pay thickness of McMurray-Wabiskaw in the Athabasca Area43
Figure 3-5 Athabasca cross section44
Figure 3-6 Correlation chart of Lower Cretaceous bitumen deposits at Athabasca Oil Sand45
Figure 3-7 Oil Sands at Cold Lake area48
Figure 3-8 Correlation chart of Lower Cretaceous at Cold Lake area 48
Figure 3-9 Clearwater Formation at Cold Lake area49
Figure 3-10 Lower Grand Rapids Formation at Cold Lake area 50
xii
Figure 3-11 Upper Grand Rapids Formation at Cold Lake area 51
Figure 3-12 McMurray Formation at Cold Lake area52
Figure 3-13 Location of Lloydminster area 54
Figure 3-14 Correlation chart of Lower Cretaceous at Lloydminster area55
Figure 3-15 Distribution of Ribbon-Shaped Manville Group at Lloydminster area57
Figure 3-16 Lloydminster area oil field59
Figure 4-1 Schematic of Experimental Set-up 63
Figure 4-2 Physical model Schematic 65
Figure 4-3 Physical Model66
Figure 4-4 Thermocouple location in Physical Model 67
Figure 4-5 Pressure cooker 68
Figure 4-6 Temperature Probe design 68
Figure 4-7 Permeability measurement apparatus69
Figure 4-8 HAAKE viscometer 70
Figure 4-9 Dean-Stark distillation apparatus 72
Figure 4-10 Sand extraction apparatus72
Figure 4-11 Bitumen saturation step75
Figure 4-12 InjectionProduction and sampling stage 76
Figure 4-13 Bottom layer of the model after SAGD experiment and the sampling points
for sand analysis77
Figure 5-1 3-D schematic of Athabasca reservoir model 81
Figure 5-2 Cross view of Athabasca reservoir model 81
Figure 5-3 Temperature dependency of bitumen modelrsquos Viscosity for Athabasca 83
Figure 5-4 Water-oil relative permeability 84
Figure 5-5 Relative permeability sets for DW well pairs 85
Figure 5-6 Schematic representation of various well configurations for Athabasca Reservoir 87
Figure 5-7 Oil Production Rate Base Case 89
Figure 5-8 Oil Recovery Factor Base Case 89
Figure 5-9 Cumulative Steam Oil Ratio (cSOR) Base Case90
xiii
Figure 5-10 Steam Chamber Volume Base Case 90
Figure 5-11 Cross view of chamber development at 4 specified time frames Base Case 91
Figure 5-12 Steam Quality of DW vs SS during the SAGD life period Base Case 91
Figure 5-13 Pressure Profile between Injector and Producer at the heel and toe Base Case93
Figure 5-14 Comparison of numerical and analytical solutions Base Case 94
Figure 5-15 Oil Production Rate Vertical Inter-well Distance Optimization 96
Figure 5-16 Oil Recovery Factor Vertical Inter-well Distance Optimization96
Figure 5-17 Steam Oil Ratio Vertical Inter-well Distance Optimization 97
Figure 5-18 Steam Chamber Volume Vertical Inter-well Distance Optimization 97
Figure 5-19 Oil Production Rate Vertical Injectors99
Figure 5-20 Oil Recovery Factor Vertical Injectors 99
Figure 5-21 Steam Oil Ratio Vertical Injectors 100
Figure 5-22 Steam Chamber Volume Vertical Injectors100
Figure 5-23 Oil Production Rate Reverse Horizontal Injector102
Figure 5-24 Oil Recovery Factor Reverse Horizontal Injector 102
Figure 5-25 Steam Oil Ratio Reverse Horizontal Injector 103
Figure 5-26 Steam Chamber Volume Reverse Horizontal Injector103
Figure 5-27 3-D View of Chamber Growth Reverse Horizontal Injector 104
Figure 5-28 Oil Recovery Factor Inclined Injector 105
Figure 5-29 Steam Oil Ratio Inclined Injector105
Figure 5-30 Oil Production Rate Inclined Injector Case 07 106
Figure 5-31 Oil Recovery Factor Inclined Injector Case 07 106
Figure 5-32 Steam Oil Ratio Inclined Injector Case 07107
Figure 5-33 Steam Chamber Volume Inclined Injector Case 07 107
Figure 5-34 Oil Production Rate Parallel Inclined Injector 109
Figure 5-35 Oil Recovery Factor Parallel Inclined Injector 109
Figure 5-36 Steam Oil Ratio Parallel Inclined Injector110
Figure 5-37 Steam Chamber Volume Parallel Inclined Injector 110
Figure 5-38 Oil Production Rate Multi-Lateral Producer111
xiv
Figure 5-39 Oil Recovery Factor Multi-Lateral Producer 112
Figure 5-40 Steam Oil Ratio Multi-Lateral Producer 112
Figure 5-41 Steam Chamber Volume Multi-Lateral Producer 113
Figure 5-42 3-D schematic of Cold Lake reservoir model 114
Figure 5-43 Viscosity vs Temperature for Cold Lake bitumen 115
Figure 5-44 Schematic representation of various well configurations for Cold Lake 117
Figure 5-45 Oil Production Rate Base Case 119
Figure 5-46 Oil Recovery Factor Base Case 119
Figure 5-47 Steam Oil Ratio Base Case120
Figure 5-48 Steam Chamber Volume Base Case 120
Figure 5-49 Oil Production Rate Vertical Inter-well Distance Optimization 121
Figure 5-50 Oil Recovery Factor Vertical Inter-well Distance Optimization122
Figure 5-51 Steam Oil Ratio Vertical Inter-well Distance Optimization 122
Figure 5-52 Steam Chamber Volume Vertical Inter-well Distance Optimization 123
Figure 5-53 Oil Production Rate Offset Horizontal Injector 124
Figure 5-54 Oil Recovery Factor Offset Horizontal Injector125
Figure 5-55 Steam Oil Ratio Offset Horizontal Injector 125
Figure 5-56 Steam Chamber Volume Offset Horizontal Injector 126
Figure 5-57 Oil Production Rate Vertical Injectors127
Figure 5-58 Oil Recovery Factor Vertical Injectors 128
Figure 5-59 Steam Oil Ratio Vertical Injectors 128
Figure 5-60 Steam Chamber Volume Vertical Injectors129
Figure 5-61 Oil Production Rate Reverse Horizontal Injector130
Figure 5-62 Oil Recovery Factor Reverse Horizontal Injector 131
Figure 5-63 Steam Oil Ratio Reverse Horizontal Injector 131
Figure 5-64 Steam Chamber Volume Reverse Horizontal Injector132
Figure 5-65 Oil Production Rate Parallel Inclined Injector 133
Figure 5-66 Oil Recovery Factor Parallel Inclined Injector 133
Figure 5-67 Steam Oil Ratio Parallel Inclined Injector134
xv
Figure 5-68 Steam Chamber Volume Parallel Inclined Injector 134
Figure 5-69 Oil Production Rate Parallel Reverse Upward Injector 135
Figure 5-70 Oil Recovery Factor Parallel Reverse Upward Injector 136
Figure 5-71 Steam Oil Ratio Parallel Reverse Upward Injector 136
Figure 5-72 Steam Chamber Volume Parallel Reverse Upward Injector137
Figure 5-73 Oil Production Rate Multi-Lateral Producer138
Figure 5-74 Oil Recovery Factor Multi-Lateral Producer 139
Figure 5-75 Steam Oil Ratio Multi-Lateral Producer 139
Figure 5-76 Steam Chamber Volume Multi-Lateral Producer 140
Figure 5-77 Reservoir deformation model141
Figure 5-78 Oil Production Rate C-SAGD 142
Figure 5-79 Oil Recovery Factor C-SAGD 143
Figure 5-80 Steam Oil Ratio C-SAGD 143
Figure 5-81 Steam Chamber Volume C-SAGD144
Figure 5-82 Schematic of SAGD and Steamflood145
Figure 5-83 3-D schematic of reservoir model for Lloydminster reservoir147
Figure 5-84 Temperature dependency of heavy oil modelrsquos Viscosity 149
Figure 5-85 Schematic of various well configurations for Lloydminster reservoir150
Figure 5-86 Oil Procution Rate Offset Producer152
Figure 5-87 Oil Recovery Factor Offset Producer 152
Figure 5-88 Steam Oil Ratio Offset Producer153
Figure 5-89 Steam Chamber Volume Offset Producer 153
Figure 5-90 Oil Production Rate Vertical Injector 155
Figure 5-91 Oil Recovery Factor Vertical Injector 155
Figure 5-92 Steam Oil Ratio Vertical Injector 156
Figure 5-93 Steam Chamber Volume Vertical Injector 156
Figure 5-94 Oil Production Rate C-SAGD 158
Figure 5-95 Oil Recovery Factor C-SAGD 158
xvi
Figure 5-96 Steam Oil Ratio C-SAGD 159
Figure 5-97 Steam Chamber Volume C-SAGD159
Figure 5-98 Oil Production Rate ZIGZAG160
Figure 5-99 Oil Recovery Factor ZIGZAG161
Figure 5-100 Steam Oil Ratio ZIGZAG 161
Figure 5-101 Steam Chamber Volume ZIGZAG162
Figure 5-102 Oil Production Rate Comparison 163
Figure 5-103 Oil Recovery Factor Comparison 163
Figure 5-104 Steam Oil Ratio Comparison 164
Figure 5-105 Steam Chamber Volume Comparison 164
Figure 6-1 Permeability measurement with AGSCO Sand 169
Figure 6-2 Elk-Point viscosity profile 170
Figure 6-3 JACOS Bitumen viscosity profile 170
Figure 6-4 Oil Rate First and Second Experiment173
Figure 6-5 cSOR First and Second Experiment 173
Figure 6-6 WCUT First and Second Experiment 174
Figure 6-7 RF First and Second Experiment174
Figure 6-8 Oil Rate Second and Third Experiment 175
Figure 6-9 cSOR Second and Third Experiment 176
Figure 6-10 WCUT Second and Third Experiment 176
Figure 6-11 RF Second and Third Experiment 177
Figure 6-12 Temperature profile along the injector at 5 and 20 hours First Experiment178
Figure 6-13 Layers and Cross sections schematic of the physical model 179
Figure 6-14 Chamber Expansion along the well-pair at 01 PVinj180
Figure 6-15 Chamber Expansion along the well-pair at 02 PVinj181
Figure 6-16 Chamber Expansion along the well-pair at 05 PVinj181
Figure 6-17 Chamber Expansion along the well-pair at 06 PVinj182
Figure 6-18 Chamber Expansion along the well-pair at 078 PVinj 182
Figure 6-19 Chamber Expansion Cross View at 078 PVinj Cross-Section 1 183
xvii
Figure 6-20 Water OilGas Relative Permeability First Experiment History Match184
Figure 6-21 Match to Oil Production Profile First Experiment 185
Figure 6-22 Match to Water Production Profile First Experiment 185
Figure 6-23 Match to Steam (CWE) Injection Profile First Experiment 186
Figure 6-24 Match to Steam Chamber Volume First Experiment186
Figure 6-25 Oil Rate First and Fourth Experiment189
Figure 6-26 cSOR First and Fourth Experiment 189
Figure 6-27 WCUT First and Fourth Experiment 190
Figure 6-28 RF First and Fourth Experiment190
Figure 6-29 Temperature profile along the injector at 3 and 16 hours Fourth Experiment191
Figure 6-30 Chamber Expansion along the well-pair at 01 PVinj192
Figure 6-31 Chamber Expansion along the well-pair at 02 PVinj193
Figure 6-32 Chamber Expansion along the well-pair at 03 PVinj193
Figure 6-33 Chamber Expansion along the well-pair at 04 PVinj194
Figure 6-34 Chamber Expansion along the well-pair at 05 PVinj194
Figure 6-35 Chamber Expansion Cross View at 05 PVinj Cross Section 1 195
Figure 6-36 Water OilGas Relative Permeability Fourth Experiment History Match197
Figure 6-37 Match to Oil Production Profile Fourth Experiment 198
Figure 6-38 Match to Water Production Profile Fourth Experiment 198
Figure 6-39 Match to Steam (CWE) Injection Profile Fourth Experiment 199
Figure 6-40 Match to Steam Chamber Volume Fourth Experiment199
Figure 6-41 Oil Rate Fifth Experiment 202
Figure 6-42 3-D cSOR Fifth Experiment 202
Figure 6-43 WCUT Fifth Experiment203
Figure 6-44 RF Fifth Experiment 203
Figure 6-45 Temperature profile along the injector at 5 and 20 hours Fifth Experiment 204
Figure 6-46 Chamber Expansion along the well-pair at 01 PVinj205
Figure 6-47 Chamber Expansion along the well-pair at 02 PVinj206
Figure 6-48 Chamber Expansion along the well-pair at 03 PVinj206
xviii
Figure 6-49 Chamber Expansion along the well-pair at 04 PVinj207
Figure 6-50 Chamber Expansion along the well-pair at 05 PVinj207
Figure 6-51 Chamber Expansion along the well-pair at 065 PVinj 208
Figure 6-52 Chamber Expansion Cross View at 065 PVinj Cross Section1 208
Figure 6-53 Sampling distributions per each layer of model209
Figure 6-54 φΔSo across the middle layer fifth experiment210
Figure 6-55 φΔSo across the top layer fifth experiment211
Figure 6-56 Water OilGas Relative Permeability Fifth Experiment History Match 212
Figure 6-57 Match to Oil Production Profile Fifth Experiment 213
Figure 6-58 Match to Water Production Profile Fifth Experiment213
Figure 6-59 Match to Steam (CWE) Injection Profile Fifth Experiment 214
Figure 6-60 Match to Steam Chamber Volume Fifth Experiment 214
Figure 6-61 Oil Rate Fifth and Sixth Experiment 216
Figure 6-62 cSOR Fifth and Sixth Experiment 216
Figure 6-63 WCUT Fifth and Sixth Experiment 217
Figure 6-64 RF Fifth and Sixth Experiment 217
Figure 6-65 Temperature profile along the injector at 4 and 14 hours Sixth Experiment220
Figure 6-66 Chamber Expansion along the well-pair at 01 PVinj221
Figure 6-67 Chamber Expansion along the well-pair at 02 PVinj221
Figure 6-68 Chamber Expansion along the well-pair at 03 PVinj222
Figure 6-69 Chamber Expansion along the well-pair at 04 PVinj222
Figure 6-70 Chamber Expansion along the well-pair at 05 PVinj223
Figure 6-71 Chamber Expansion along the well-pair at 06 PVinj223
Figure 6-72 Chamber Expansion Cross View at 05 PVinj 224
Figure 6-73 φΔSo across the middle layer sixth experiment225
Figure 6-74 φΔSo across the top layer sixth experiment226
Figure 6-75 Water OilGas Relative Permeability Sixth Experiment History Match227
Figure 6-76 Match to Oil Production Profile Sixth Experiment 228
Figure 6-77 Match to Water Production Profile Sixth Experiment 228
xix
Figure 6-78 Match to Steam (CWE) Injection Profile Sixth Experiment 229
Figure 6-79 Match to Steam Chamber Volume Sixth Experiment229
Figure 6-80 Schematic representation of inclined injector pattern230
Figure 6-81 Oil Rate Fifth and Sixth Experiment 232
Figure 6-82 cSOR Fifth and Sixth Experiment 232
Figure 6-83 WCUT Fifth and Sixth Experiment 233
Figure 6-84 RF Fifth and Sixth Experiment 233
Figure 6-85 Schematic of D5 Location in inclined injector pattern 234
Figure 6-86 Temperature profile in middle of the model at 4 and 10 hours Seventh Exp 235
Figure 6-87 Chamber Expansion along the well-pair at 01 PVinj237
Figure 6-88 Chamber Expansion along the well-pair at 02 PVinj237
Figure 6-89 Chamber Expansion along the well-pair at 03 PVinj238
Figure 6-90 Chamber Expansion along the well-pair at 04 PVinj238
Figure 6-91 Chamber Expansion along the well-pair at 05 PVinj239
Figure 6-92 Chamber Expansion Cross View at 05 PVinj Cross Section 1 239
Figure 6-93 φΔSo across the top layer seventh experiment 240
Figure 6-94 Water OilGas Relative Permeability Seventh Experiment History Match242
Figure 6-95 Match to Oil Production Profile Seventh Experiment 243
Figure 6-96 Match to Water Production Profile Seventh Experiment 243
Figure 6-97 Match to Steam (CWE) Injection Profile Seventh Experiment 244
Figure 6-98 Match to Steam Chamber Volume Seventh Experiment244
xx
LIST OF SYMBOLS ABBREVIATIONS AND NOMENCLATURE
Symbol Definition
C Heat capacity Cp Centipoises cSOR Cumulative Steam Oil Ratio ERCB Energy Recourses and Conservation Board Fo Fourier Number g Acceleration due to gravity h height k Effective permeability to the flow of oil K Thermal conductivity of reservoir krw Water relative permeability krow Oil relative permeability in the Oil-Water System krg Gas relative permeability krog Oil relative permeability in the Gas-Oil System Kv1 First coefficient for Gas-Liquid K-Value correlation Kv4 Fourth coefficient for Gas-Liquid K-Value correlation Kv5 Fifth coefficient for Gas-Liquid K-Value correlation L Length of horizontal well m Viscosity-Temperature relation coefficient nw Exponent for calculating krw now Exponent for calculating krow nog Exponent for calculating krog ng Exponent for calculation krg RF Recovery Factor Sl Liquid Saturation Soi Initial Oil Saturation Soirw Irreducible oil saturation with respect to water Sgr Residual gas saturation Soirg Irreducible oil saturation with respect to gas Sw Water saturation Swcon Connate water saturation TR Reservoir temperature Ts Steam temperature U Interface velocity UTF Underground Test Facility x Horizontal distance from draining point X Dimensionless horizontal distance y Vertical distance from draining point Y Dimensionless vertical distance ΔSo Oil s aturation change
xxi
Greek Symbols
micro Dynamic viscosity νs Kinematic viscosity of bitumen at steam temperature α Thermal diffusivity φ Porosity ρ Density of oil θ Angle of Inclination of interface ζ Normal distance from the interface
CHAPTER 1
INTRODUCTION
2
11 Background Canadarsquos oil sands and heavy oil resources are among the largest known hydrocarbon
deposits in the world Alberta deposits contain more than 80 of the worldrsquos recoverable
reserves of bitumen However the amount of conventional oil reserves in Canada is
limited and these reserves are declining As a result of advances in the Steam Assisted
Gravity Drainage (SAGD) which was introduced by Butler in 1978 some of the bitumen
resources have turned into reserves These resources include the vast oil sands of
Northern Alberta (Athabasca Cold Lake and Peace River) and the more heavy oil that
sits on the border between Alberta and Saskatchewan (Lloydminster) Currently due to
the oil price and SAGDrsquos efficiency the oil sands and heavy oils are attracting a lot of
attentions
Most of the bitumen contains high fraction of asphaltenes which makes it highly
viscous and immobile at reservoir condition (11-15 ordmC) It is their high natural viscosity
that makes the recovery of heavy oils and bitumen difficult However the viscosity is
very sensitive to temperatures as shown in Fig 1-1
10000000
1000000
100000
10000
1000
100
1
Figure 1-1 μ minusT relationship
Visc
osity
cp
Athabasca Cold Lake
0 50 100 150 200 250 Temperature C
10
3
Currently there are two methods to extract the bitumen out of their deposits a) Open
pit mining b) In-Situ Recovery Using strip mining is economical for the deposit close to
surface but only about 8 of oil sands can be exploited by this method The rest of the
deposits are too deep for the shovel and truck access Currently only thermal oil recovery
methods can be used to recover bitumen from oil sands although several non-thermal
technologies are under investigation
Thermal oil recovery either by heat injection or internally generated heat through
combustion introduces heat into the reservoir to reduce the flow resistance by reduction
of the bitumen viscosity with increased temperature Thermal methods include steam
flooding cyclic steam stimulation in-situ combustion electric heating and steam
assisted gravity drainage Among these processes steam assisted gravity drainage
(SAGD) is an effective method of producing heavy oil and bitumen It unlocks billions
barrels of oil that otherwise would have been inaccessible Figure 1-2 displays a vertical
cross-section of the basic SAGD mechanism
Overburden
Underburden
Steam Chamber
Net Pay
Figure 1-2 Schematic of SAGD
In the SAGD process in order to enhance the contact area between the reservoir and
the wellbore two parallel horizontal wellbores are drilled and completed at the base of
the formation The horizontal well offers several advantages such as improved sweep
efficiency increased reserves increased steam injectivity and reduced number of wells
needed for reservoir development In the SAGD well-pair the top well is the steam
injector and the bottom well is the oil producer The vertical distance between the injector
4
and the producer is typically 5 m The producer is generally located a couple of meters
above the base of formation The SAGD process consists of three phases
1) Preheating (Start-up)
2) Steam Injection amp Oil Production
3) Wind down
The purpose of preheating period is to establish fluid communication between
injector and producer The steam is circulated in both wellbores for typically 3-4 months
in order to heat the region between the wells The intervening high viscosity bitumen is
mobilized and starts flowing from the injector to the producer as a result of both gravity
drainage and the small pressure gradient between wellbores
Once the fluid communication between injector and producer is established the
normal SAGD operation can start High quality steam is introduced continuously into the
formation through the injection well and the oil is produced through the producer The
injected steam tends to rise and expand it forms a steam saturated zone (steam chamber)
above the injection well The steam flows through the chamber where it contacts cold
bitumen surrounding the chamber At the chamber boundary the steam condenses and
liberates its latent heat of vaporization which serves to heat the bitumen This heat
exchange occurs by conduction as well as by convection The heated bitumen becomes
mobile drains by gravity together with the steam condensate to the production well along
the steam chamber boundary Within the chamber the pressure remains constant and a
counter current flow between the steam and draining fluids occurs As the bitumen is
being produced the vacated space is left behind for the steam to fill in The chamber
grows upward longitudinally and laterally before it touches the overburden Eventually it
reaches the cap rock and then spreads only laterally During the normal SAGD phase two
sub-stages can be defined Ramp-up and Plateau It is well understood that the initial
upward growth of the steam chamber is much faster than the lateral growth Meanwhile
the injection and production rates appear to increase This stage is called Ramp-Up As
the chamber reaches the formation top the lateral growth becomes dominant This period
of production in which the oil production rate reaches a maximum (and then slowly
declines) while the water cut goes through a minimum is called Plateau
5
As time proceeds the chamber spreads laterally and the interface becomes more
inclined The oil has to travel longer distance to reach the production well and larger area
of the steam chamber is exposed to the cap-rock Consequently the oil rate decreases and
the SOR increases The ultimate recovery factor in SAGD is typically higher than 50
Eventually the SOR becomes unacceptably high and the steam chamber is called
ldquomaturerdquo The Wind-Down stage begins at this point
Butler McNab and Lo derived the amount of oil flow parallel to the interface and via
drainage force through Equation (11) by assuming that the steam pressure remains
constant in the steam chamber [2] only steam flows in the chamber oil saturation in the
chamber is residual [3] drainage is parallel to the interface the effective permeability is
constant and heat transfer ahead of the steam chamber to cold part of the reservoir is
only by conduction The steam zone interface was assumed to move uniformly at a
constant velocity U Based on these assumptions the temperature ahead of the interface
is given by Equation (1 2)
T=Ts
T=TR
θ
dt t x
y ⎟ ⎠ ⎞
⎜ ⎝ ⎛ part
part
Figure 1-3 Vertical cross section of drainage interface [2]
2φΔS kg h αo (11)q = 2L mν s
T Tminus S ⎛ Uξ ⎞ = exp ⎜ minus (12)⎟T minusT αS R ⎝ ⎠
where q rate of drainage of oil along the interface
L Length of horizontal well φ porosity
ΔSo Oil saturation change
6
k Effective permeability to the flow of oil g Gravitational acceleration α Thermal diffusivity h Reservoir net pay
m Viscosity-Temperature relation coefficient υ s Kinematic viscosity of bitumen at steam temperature Ts Steam temperature
TR Reservoir temperature U Interface velocity ξ Normal distance from the interface
The major assumption for flow relation derivation was that the steam chamber was
initially a vertical plane above the production well and the horizontal displacement was
given as a function of time t and height y by
kgαx t= (13a)2φΔS m ( ) minuso ν s h y
kgα ⎛ ⎞t 2
= minus (13b)y h ⎜ ⎟2φΔS m ⎝ ⎠o ν s x
The position of the interface in dimensionless form can be written as
1 tD 2
Y 1 (14) = minus ⎛ ⎞ ⎜ ⎟2 X⎝ ⎠
X = x h (15)
Y = y h (16)
t kg α (17) t = D h S m h φΔ o ν s
where x Horizontal distance from draining point y Vertical distance from draining point
X Dimensionless horizontal distance Y Dimensionless vertical distance
Interface positions described by equation (14) are shown in Figure 1-4
7
0
01
02
03
04
05
06
07
08
09
1
0 05 1 15 2 Horizontal Distance xh
Ver
tical
Dist
ance
yh
02 06
04 08
1 12
14 16
18 2
Figure 1-4 Steam chamber interface positions
The m value is introduced in Equation (18) to account for the effect of temperature
on viscosity It is defined as a function of the viscosity-temperature characteristics of the
oil the steam and the reservoir temperature
⎡ TS ⎛ 1 1 ⎞ dT ⎤minus1
m = ⎢ν minus ⎥ (18) ν ν T T⎣
s intTR ⎜⎝ R
⎟⎠ minus R ⎦
The drainage rate dictated by equation (11) is exaggerated compared with
experiment data Butler and Stephens modified this theory and came up with the
TANDRAIN theory in which the drainage rate is given by Equation 19 [4] This rate is
87 of that calculated by equation (11) and is closer to the experiment data
15φΔS kg h αoq = 2L (19) mν s
The interface in Figure 14 was modified so that the interface will not spread
horizontally to infinity In TANDRAIN theory the interface is connected to the horizontal
well as in Figure 1-5
8
Figure 1-5 Interface Curve with TANDRAIN Theory
Butler analyzed the dimensional similarity of the process in the field and laboratory
scale physical models and found that not only tD must be the same for the model and the
field but also a dimensionless number B3 as given by equation (110) must be the same
[3]
3 o s
kgh B S mαφ ν
= Δ
(110)
B3 is obtained by combining the dimensionless time (tD) and Fourier number
Fourier number is a dimensionless number that is the ratio of heat conduction rate and
thermal energy storage rate Butler expressed the extent of the temperature in a solid that
is heated by conduction can be demonstrated by Fourier number as provided in equation
(111) [1]
αtFo = h2 (111)
For dimensional similarity between a laboratory model and field in addition to tD
Fo needs to be the same for both models Since Butler defined B3 as
B3 = tD (113) Fo
Therefore for dimensional similarity between filed and lab model the B3 of both
models has to be equal
9
12 Dimensional Analysis Dimensional analysis is a practical technique in all experimentally based areas of
engineering research It can be considered as a simplified type of scaling argument for
learning about the dependence of a phenomenon on the dimensions and properties of the
system that exhibits the phenomenon Dimensional analysis is a method for reducing the
number and complexity of experimental variables that affect a given physical
phenomena If it is possible to identify the factors involved in a physical situation
dimensional analysis can form a relationship between them Dimensional analysis
provides some advantages such as reducing number of variables defining dimensionless
equations and establishing dimensional similarity (Scaling law) Out of the listed
advantages the scaling law allows evaluating the full process using a small and simple
model instead of constructing expensive large full scale prototypes Particular type of
similarities is geometric kinematic and dynamic similarity To establish ldquoSimilar
systemsrdquo one should choose identical values of dimensionless combinations between two
systems even though the dimensional quantities may be quite different Usually the
dimensionless combinations are expressed as dimensionless number such as Re Fr and
etc Similarity analyses can proceed without knowledge of the governing equations
However when the governing equations are known then the ldquoscale analysisrdquo term is
more suitable Since this research is dealing with thermal methods therefore the scaling
requirements for thermal models need to be considered These requirements can be
generalized as follows
1 Geometric Similarity field and model must be geometrically similar This implies
the same width-to-length ratio height-to-length ratio dip angle and reservoir
heterogeneities
2 The values of several parameters containing fluid and rock properties as well as
terms related to the transport of heat and mass must be equal in the field and
model
3 Field and model must have the same initial conditions and boundary conditions
Scaled model experiments are one of the more useful tools for study and further
development of the SAGD process Before SAGD is applied in a new field laboratory
physical model experiments and field pilots may investigate its performance under
10
various reservoir conditions and geological characteristics Physical model studies can
investigate the effects of related factors by evaluating various scenarios Such models
can be used to optimize the pattern type size well configurations injection and
production mode and effects of additives By careful scaling the physical model can
produce data to forecast the performance of reservoirs under realistic conditions It
provides a helpful guide for prediction of field applications and for economic evaluation
In order to obtain the scaled analysis in a SAGD process it is essential to set equal
values of B3 in Equation 110 for both the physical model and the field properties The
properties of the scaled model are selected such a way that the dimensionless number B3
is the same for the model as for the field A list of the parameters included in scaling
analysis is provided in Table 11
Table 1-1 Effective parameters in Scaling Analysis of SAGD process
Parameter
Net Pay m
Permeability mD
φΔSo
microR cp
micros cp
m
13 Factors Affecting SAGD Performance The parameters that control the SAGD performance can be categorized as reservoir
properties well design and operating parameters The following provides a brief
discussion of the effects of important parameters
131 Reservoir Properties
1311 Reservoir Depth
One of the important parameters affecting SAGD performance is the reservoir depth
Deep reservoirs have higher operating pressure which means higher steam temperature
Higher pressure steam (to some extend) carries higher enthalpy (but lower latent heat)
11
and has lower specific volume This increases the energy stored in the vapor chamber
Also the heat losses in the well bore and to the overburden increase due to higher
temperature and increased tubing length On the positive side increased temperature
provides lower oil viscosity The net effect of reservoir depth on SOR and RF needs to
be examined in order to determine the optimum range of reservoir depth
1312 Pay Thickness Oil Saturation Grain Size and Porosity
Net pay thickness oil saturation and porosity determine the amount of oil in the
reservoir and higher values yield better oil rate lower steam oil ratio and higher recovery
factor The minimum pay thickness needed for economically viable SAGD operations
appears to be about 15 meters but this needs to be further examined
1313 Permeability (kv kh)
Permeability determines how easily the fluids flow in the reservoir thus it directly
affects the production rate Low vertical permeability especially between injector and
producer will hinder steam chamber development High horizontal permeability helps
the lateral spreading of steam chamber In most laboratory experiments the physical
models are packed with glass beads or sand that give isotropic permeability (kvkh = 1)
1314 Bitumen viscosity
Heavy oils and bitumen contain a higher fraction of asphaltenes are highly viscous
and sometimes immobile at reservoir condition It is their high natural viscosity that
makes the recovery of heavy oils and bitumen difficult The oil drainage rate in SAGD
under pseudo-steady-state conditions depends on the heated oil viscosity However the
time required for establishing the communication between the injector and the producer
depends largely on the original oil viscosity When the original oil viscosity is lower and
the oil is sufficiently mobile the communication between the wells is no longer a hurdle
This opens up the possibility of increasing the distance between the two wells and
introducing elements of steam flooding into the process
1315 Heterogeneity
A significant concern in the development of the SAGD process is that of the possible
effects of barriers to vertical flow within the reservoir These may consist of significant
sized shale layers or may be grain-sized barriers whose effect is reflected by a lower
12
vertical than horizontal permeability In some situations continuous and extensive shale
barriers divide the reservoir and each sub-reservoir has to be drained separately
However it is common to find layers of shale a few centimeters thick but of relatively
limited horizontal length which do not divide the reservoir but make it necessary for
fluids to meander around them if they are to flow vertically It is important to note that
the direction of flow is oblique not vertical It is the permeability in the direction of flow
that determines the rate not the vertical permeability [3] Overall it appears that partial
shale barriers can be tolerated by the process
In addition to the effect of limited extent shale barriers it would be desirable to
evaluate the effect of heterogeneity due to permeability difference in layers In some
cases the reservoir contains horizontal layers of different permeability so there will be
two cases
frac34 Low permeability on top of high permeability
frac34 High permeability on top of low permeability
Beside the effect of shale barriers on vertical flow their presence results in higher
cSOR Due to their presence in forms of non productive rock within the oil bearing zone
they will be heated as well as the oil sand This extra heat which does not yield to any
additional oil production will cause the cSOR to increase
1316 Wettability
Wettability controls the distribution and flow of immiscible fluids in an oil reservoir
and thus plays a key role in any oil-recovery process Once thought to be a fixed property
of each individual reservoir it is now recognized that wettability can vary on both
microscopic and macroscopic scales The potential for asphaltenes to adsorb onto high
energy mineral surfaces and thus to affect reservoir wettability has long been recognized
The effect of wettability on SAGD performance has not been adequately evaluated
However it is apparent that the wettability will affect oil-water relative permeability and
residual oil saturation which in turn would affect the gravity drainage of oil and ultimate
recovery
13
1317 Water Leg
Many heavy oil and oil sand reservoirs are in communication with water sand(s)
Depending on the density (oAPI gravity) of oil the water sand could lie above or below
the oil zone The presence of a bottom water layer has less an impact on recovery than the
case where an overlying water layer is present Steam flooding a heavy oil or oil sand
reservoir with confinedunconfined water sand (water which may lie below or above the
oil-bearing zone) is risky due to the possibility of short circuiting the oil-bearing zone
There is a major concern that the existence of thief zones such as top water will have
detrimental effects on the oil recovery in (SAGD) process [3] For underlying aquifers if
the steam chamber pressure is high enough and stand-off distance of the producer is
selected correctly then intrusion of water may be prevented
1318 Gas Cap
Some of the heavy oil reservoirs have overlying gas caps Some SAGD studies have
suggested that gas-cap production might ldquosterilizerdquo the underlying bitumen [2] Many
such studies however assumed rather thick continuous pays with high permeability and
considered a large gas-cap So considering the case of a small gas-cap on top of the oil
sand formation with different well configurations (including vertical injectors) would
clarify the feasibility of SAGD projects in such reservoirs
132 Well Design
1321 Completion
SAGD wells are completed with a sand control device in the horizontal section Trials
have been run with wire-wrapped screens but most operators use slotted liners Slotted
liners are manufactured by cutting a series of longitudinal slots The slot width is
selected based on the formationrsquos grain-size distribution to restrict sand production and
allow fluid inflow Liner design requirements must balance sand retention open fluid
flow area and structural capacity Larger liner which means larger intermediate casing
and larger holes will reduce pressure drop especially near the heel of injector It must be
decided which liner size would be optimum for the well
14
1322 Well configuration
The most common well configuration for SAGD operation is to place a single
horizontal injector directly above a single horizontal producer The total number of wells
in such a pattern is two with an injector-to-producer ratio of 11 Based on heavy oil
reservoir oil viscosity (either mobile oil or bitumen) at reservoir condition kvkh
heterogeneity and other factors it might be advantageous to place the injector and
producer in other configurations than the base case of 5 m apart horizontal wells in the
same vertical plane
1323 Well Pairs Spacing
In the initial stage of SAGD the upward rate of growth of the steam chamber would
be larger than the rate of sideways growth Eventually the upward growth is limited by
the top of the reservoir and the sideward growth then becomes critical After a period of
time the interfaces of different chambers intermingle and form a single steam layer above
the oil It would be beneficial to optimize the distance between well pairs since smaller
spacing would yield better SOR and recovery factor but the oil production would decline
faster and more wells would be required
1324 Horizontal well length
The main advantage of long horizontal well in thermal oil recovery is to improve
sweep efficiency enhance producible reserves increase steam injectivity and reduce
number of wells needed for reservoir development The longer well length would yield
higher rates but causes higher pressure drop and it may require larger pipes and holes to
accumulate the higher flow rates and to reduce the pressure drop A sensitivity analysis
must be done to determine the optimum length
133 Operational Parameters
1331 Pressure
Operating pressure plays a significant role in the rate of recovery Lower operating
pressure reduces the SOR reduces H2S production may reduce the silica dissolution and
thereby reduce the water treatment issues [5] However lower pressure operation
increases the challenges in lifting the fluid to the surface A low pressure SAGD
operation may end up with a low recovery factor during the economic life of the project
15
the remaining reserve may be lost forever as it will be extremely unlikely that an
additional SAGD project would be undertaken in the future to ldquoreworkrdquo the property On
the other hand a bitumen deposit which is below the current economic threshold may
well become an attractive prospect in the future with advances in technology simply
because it remains intact Higher steam pressure will cause greater dilation of sandstone
thereby increasing effective reservoir porosity which in turn it is predicted will have the
result of significantly improving projected SAGD recoveries It may be beneficial to
accelerate the start-up and initial steam chamber development and provide sufficient
pressure to lift production fluid to surface
1332 Temperature
At the lower steam temperature which is related to the pressure the sand matrix is
heated to a lower temperature and the energy requirement for heating the reservoir goes
down Conceptually this should lead to a lower steam oil ratio However the lower
temperature would increase the heated oil viscosity and reduce the oil drainage rate
thereby increasing the project time span This will increase the time available for heat
loss to the overburden and may partially or totally negate the reduced heat requirements
Although the steam temperature is often determined by the prevailing reservoir
pressure in situations where operating flexibility exists the optimum temperature needs
to be determined When a non-condensable gas is injected with the steam the pressure
can be increased above the saturation pressure of steam by adding more gas
1333 Pressure Difference between Injector and Producer
Once the reservoir between the two wells is sufficiently heated and bitumen mobility
is evident a pressure differential is applied between the wells The risk in applying this
pressure differential is creating a preferential flow path between wells which results in
the inefficient utilization of energy and may damage the production linear Determining
when to induce this pressure differential and how much pressure differential to apply is
critical to overall optimization of the process
1334 Subcool (Steam-trap control)
The steam circulation is aimed at establishment of the connectivity between injector
and producer Once the communication between the wells is achieved the SAGD process
16
is switched into the normal injection-production process Over this period the steam may
break into the producer and by-pass the heated bitumen In order to decrease the risk of
such steam breakthrough a back pressure is imposed on the production well which
creates level of liquid above the production well which is called subcool The subcool can
be either high or low pressure In the high pressure subcool the liquid level decreases
while in the low pressure one it increases In a field project the sucool varies between
high and low pressures at different time periods Optimization of the subcool amount and
implementation time frame requires intensive investigations
1335 Steam Additives
In SAGD process addition of hydrocarbon solvents for mobility control may play an
important role Components of hydrocarbon solvents based on their PVT behavior may
penetrate into immobile bitumen beyond the thermal boundary layer This provides
additional decrease in viscosity due to dilution with lighter hydrocarbons in that zone
Different solvent mixtures with varying compositions can be employed for achieving
enhancement in SAGD recovery
1336 Non-Condensable Gas
In the practical application of SAGD process the steam within the steam chamber can
be expected to contain non-condensable gases methane and carbon dioxide Carbon
dioxide is often found in the produced gas from thermal-recovery projects and its source
is thought to be largely from the rocks within the chamber The small amounts of non-
condensable gas can be beneficial because the gases accumulate at the top edges of the
steam chamber and restrict the rate of the heat loss to the overburden [3] The non-
condensable gases may not increase the ultimate recovery but will decrease the SOR
However presence of too much non-condensable gas can reduce the steam chamber
temperature and interfere in the heat transfer process at the edge of the chamber
1337 Wind down
The last stage for SAGD operation is wind down It can be done by either low quality
steam or some non condensable gases Based on field experiences it was proposed to use
low quality steam In order to find the level of this low quality some sensitivity analysis
17
must be done to find the best time for applying the wind down and also the possibility of
adding some non condensable gases
14 Objectives Since mid 1980rsquos SAGD process feasibility has been field tested in many successful
pilots and subsequently through several commercial projects in various bitumen and
heavy oil reservoirs Although SAGD has been demonstrated to be technically successful
and economically viable it still remains very energy intensive extremely sensitive to
geological and operational conditions and an expensive oil recovery mechanism A
comprehensive qualitative understanding of the parameters affecting SAGD performance
was provided in the previous section Well configuration is one of the major factors
which require greater consideration for process optimization Over the 20 years of SAGD
experience the only well configuration that has been extensively field tested is the
standard 11 configuration which has a horizontal injector lying approximately 5 meters
above a horizontal producer
The main objective of this study is to evaluate the effect of well configuration on
SAGD performance and develop a methodology for optimizing the well configurations
for different reservoir characteristics The role of well configuration in determining the
performance of SAGD operations was investigated with help of numerical and physical
models Numerical modeling was carried out using a commercial fully implicit thermal
reservoir simulator Computer Modeling Group (CMG) STARS The wellbore modeling
was utilized to account for frictional pressure drop and heat losses along the wellbore A
3-D physical model was designed based on the available dimensional analysis for a
SAGD type of recovery mechanism Physical model experiments were carried out in the
3-D model With this new model novel well configurations were tested
1 The most common well configuration for SAGD operation is 11 ratio pattern in
which a single horizontal injector is drilled directly above a single horizontal
producer However depending on the reservoir and oil properties it might be
advantageous to drill several horizontalvertical wells at different levels of the
reservoir ie employ other configurations than the base case one to enhance the
drainage efficiency In this study three types of bitumen and heavy oil reservoirs
18
in Alberta Athabasca Cold Lake and Lloydminster were considered for
evaluating the effects of well configuration For example in heavy oil reservoirs
containing mobile oil at the reservoir condition it may be advantageous to use an
offset between injector and producer Figure 1-5 presents some of the modified
well configurations that can be used in SAGD operations These well
configurations need to be matched with specific reservoir characteristics for the
optimum performance None of them would be applicable to all reservoirs The
aim of this research was to investigate the conditions under which one or more of
these well configurations would give improved performance When two parallel
horizontal wells are employed in SAGD the relevant configuration parameters
are (a) height of the producer above the base of the reservoir (b) the vertical
distance between the producer and the injector and (c) the horizontal separation
between the two wells which is zero in the base case configuration (d) well
length of well-pairs The effects of these parameters in different types of
reservoirs were evaluated with numerical simulation and some of the optimized
configurations were tested in the 3-D physical model
2 Hybrids of vertical and horizontal well pairs were also evaluated to see the
potentials of bringing down the cost by using existing vertical wells
3 The most promising well patterns would be experimentally evaluated in the 3-D
physical model
4 The results of physical model experiments will be history matched with reservoir
simulators to validate the simulations and to extend the simulations to the field
scale for performance predictions
19
Basic Well Configuration Reversed Horizontal Injector
Injector InjectorsInjector Produce
Producer Producer
Injectors Multi Lateral Producer Top View
Injector
Injector Producer Producer Producer
C-SAGD Vertical Injector Inclined Injector
Figure 1-6 Various well configurations
15 Dissertation Structure This study comprised seven chapters of which Chapter 1 describes the basic
concepts of SAGD process a review on dimensional analysis for SAGD explanation of
effective parameters on SAGD and eventually the research objectives
Chapter two provides a general review on previous researches on SAGD This
includes both numerical and experimental studies achieved to evaluate SAGD In
addition extensive literature reviews of proposed well configuration in SAGD process
are provided Most of commercial SAGD projects in three reservoirs of Athabasca Cold
Lake and Lloydminster are described in chapter two as well
In Chapter three a simple geological description of Athabasca Cold Lake and
Lloydminster reservoirs is provided The sequence and description of different formation
for each reservoir is explained and their properties such as porosity permeability and oil
saturation are provided The target formations of most commercial projects are referred
In Chapter four the experimental apparatus which comprised several components
such as steam generator data acquisition temperature probes and physical model is well
described The prepost experimental analysis was achieved in series of equipments such
as permeability measurement apparatus viscometer and dean stark distillation Each
equipment was described briefly The experimental methods and procedures are
explained in this chapter as well
Chapter five discusses the numerical simulation studies conducted to optimize the
well configuration for Athabasca Cold Lake and Lloydminster reservoirs The well
20
constraints operating condition and input data such as description of the geological
models and PVT data for each reservoir are presented This chapter outlines the
comparison of different well patterns results with the base case results for each reservoir
Based on the RF and cSOR results some new well patterns are recommended for each
reservoir
Chapter six comprises the presentation and discussion of the experimental results
Three sets of well patterns are examined for Athabasca and Cold Lake type of reservoir
Each well pattern is compared against the basic SAGD pattern The results of each
experiment are analysed and described in detail Eventually each test was history
matched using CMG-STARS
Chapter seven summarizes the contribution and conclusions of this research in
optimizing the SAGD process under new well configuration both numerically and
experimentally Some future recommendations and research areas are provided in this
chapter as well
CHAPTER 2
LITERATURE REVIEW
22
21 General Review Thermal recovery processes involves several mechanisms such as a) reduction of the
fluid viscosity resistance against the flow via introducing heat in the reservoir b)
distillationcracking of heavy components into lighter fractions Since distillation and
cracking requires specific conditions such as high temperature at low pressures or super
high temperature at high pressures therefore the dominant mechanism in thermal
recovery methods is viscosity reduction In thermal techniques steam fire or electricity
are employed to heat the oil and reservoir
Among all fluids water is abundant and has exceptionally high latent heat of
vaporization which makes it the best heat carrier for thermal purposes Therefore within
all thermal methods steam based recovery methods have become the most efficient for
exploiting bitumen and heavy oil At the same time steam mobility is also very high
Consequently combining the gravitational force and mobility difference of bitumen and
steam would cause the steam to easily penetrate rise into and override within the
reservoir These characteristics are taken advantage of in the SAGD process In fact
using horizontal well-pairs in SAGD causes the steam chamber to expand gradually and
drain the heated oil and steam condensate from a very large area even though the well-
pairs are drilled in the vicinity of each other and the chance of steam breakthrough in the
production well is high
SAGDrsquos efficiency has been compared to the prior field-tested thermal methods such
as steam flood or CSS In steam flooding as a result of steam and crude oil density
difference the lighter steam tends to override and it can breakthrough too early in the
process However being a gravity drainage process SAGD overcomes this limitation of
steam flooding SAGD offers specific advantages over the rest of thermal methods
a) Smooth and gradual fluid flow Unlike the steam flood and CSS less oil will be
left behind
b) No steam override or fingering
c) Moderate heat loss which yields higher energy efficiency
d) Possibility of production at shallow depths
e) Stable gravitational flow
f) Production of heated oil at high rates resulting in faster payout time
23
Since the 1980lsquos the use of shovels and trucks have dominated tar sands mining
operations [2] Using strip mining is still economical for the deposits that are close to
surface but the major part of the oil sand deposits is too deep to strip mine As the depth
of deposit increases using thermal and non-thermal in situ recovery methods becomes
vital
SAGD was first developed by Butler et al [2] A mathematical model was proposed to
predict the production of SAGD based on a steady state assumption Through years of
experiments and field pilot applications the understanding of SAGD process has been
greatly broadened and deepened
Butler further estimated the shape of the steam chamber During the early stage of
steam chamber growth the upward motion of the interface is in the form of steam fingers
with oil draining around them while subsequently the lateral and downward movement of
the interface takes a more stable form [6]
Alberta Oil Sands have seen over 30 years of SAGD applications and numerous
numerical and experimental studies have been conducted to evaluate the performance of
SAGD process under different conditions The experimental models used in laboratory
studies were mostly 2-D models
Chung and Butler examined geometrical effect of steam injection on SAGD two
scenarios (spreading steam chamber and rising steam chamber) were established to
elucidate the geometrical effect of steam injection on wateroil emulsion formation in the
SAGD process [7]
Zhou et al conducted different experiments on evaluation of horizontalvertical well
configuration in a scaled model of two vertical wells and four horizontal well for a high
viscosity oil (11000 cp) The main objective was to compare the feasibility of steam
flood and SAGD in a high mobility reservoir The results showed that a horizontal well-
pair steam flood is more suitable than a classic SAGD [8]
Experiments and simulation were also carried out by Nasr and his colleagues [9] A
two-dimensional scaled gravity drainage experiment model was used to calibrate the
simulator The results obtained from simulation promoted insight into the effect of major
parameters such as permeability pressure difference between well pair capillary pressure
and heat losses on the performance of the process [9]
24
Chan [10] numerically modeled SAGD performance in presence of an overlying gas
cap and an underlying aquifer It was pointed out that the recovery in these situations may
be reduced by up to 20-25 depending on the reservoir setting
Nasr and his colleagues ran different high pressure tests with and without naphtha as
an additive Steam circulation was eliminated and two methods to enhance recovery were
proposed as they believed steam circulation causes delay in oil production [11]
Sasaki [12 13] reported an improved strategy to initialize the communication
between the injector and producer An optical-fiber scope with high resolution was used
together with thermocouples to better observe the temperature distribution of the model
It was found that oil production rate increased with increasing vertical spacing however
the initiation time of the start of production was postponed A modified process was
proposed to tackle this problem
Yuan et al [14] investigated the impact of initial gas-to-oil ratio on SAGD
performance A numerical model was validated through history matching experimental
tests and thereafter the numerical model was utilized for further study Based on the
results they could not conclude the exact impact of the gas presence They stated that it
mostly depends on reservoir conditions and operations
Different aspects of improving SAGD performance were discussed by Das He
showed that low pressure has two advantages of lower H2S generation and less silica
production but has a tendency to require artificial lift [5]
The start-up phase of the SAGD process was optimized using a fully coupled
wellborereservoir simulator by Vanegas Prada et al [15] They conducted a series of
sensitivity runs for evaluating the effects of steam circulation rate tubing diameter
tubing insulation and bottom hole pressure for three different bitumen reservoirs
Athabasca Cold Lake and Peace River
The production profile in SAGD process consists of different steps such as
Circulation Ramp-up Plateau and Wind-down Li et al [16] studied and attempted to
optimize the ramp-up stage The effect of steam injection pressure on ramp-up time and
the associated geo-mechanical effect were investigated as well The results demonstrated
that the higher injection pressure would reduce the ramp-up period and consequently the
contribution of the geo-mechanical effect in the ramp-up period would be greater [16]
25
Barillas et al [17] studied the performance of the SAGD for a reservoir containing a
zone of bottom water (aquifer) The effect of permeability barriers and vertical
permeability on the cumulative oil was investigated Their result was a bit unusual since
they concluded that the lower kvkh would increase the oil recovery factor [17]
Albahlani and Babadagli [18] provided an extensive literature review of the major
studies including experimental and numerical as well as field experience of the SAGD
process They reviewed the SAGD steps and explained the role of geo-mechanical and
operational effects [18]
The effects of various operational parameters on SAGD performance were discussed
in the previous chapter However the geological (reservoir) characteristics and
heterogeneities play the most significant role in recovery process performance While
every single reservoir property has a specific impact on SAGD process heterogeneity is
the most critical aspect of the reservoir which has a direct effect on both injection and
production behavior Heterogeneity may consist of significant sized shale layers or may
be grain-sized barriers whose effect is reflected by a lower vertical than horizontal
permeability A significant concern in the development of the SAGD process is that of
the possible effects of barriers to vertical flow within the reservoir
Yang and Butler [19] conducted several experiments using heterogeneity in their
physical model Various scenarios such as two layered reservoir high permeability
above low permeability and low permeability above high permeability long horizontal
barrier short horizontal barrier and tilted barrier The results demonstrated that in the two
layered reservoir a faster production rate would be achieved when the high permeability
layer is located above the low permeability zone In addition they showed that the short
horizontal barrier does not affect the process [19]
Chen and Kovscek [20] numerically studied the effect of heterogeneity on SAGD A
stochastic model in which the reservoir heterogeneity in the form of thin shale lenses was
randomly distributed throughout the reservoir Besides shale heterogeneity effect of
natural and hydraulic fractures was studied as well [20]
Several studies were conducted to evaluate the contribution of various parameters in
the SAGD process One of the parameters that control the SAGD performance is the well
configurations Over the life of SAGD the only well configuration that has been field
26
tested is the standard 11 configuration which has a horizontal injector lying
approximately 5 meters above a horizontal producer in the same vertical plane On the
course of well configuration some 2-D experimental and 3-D numerical simulations were
conducted which mostly compared the efficiency of vertical vs horizontal injectors It
seems that well configuration is an area that has not received enough attention
Chung and Butler tested two different well configurations the first scheme used
parallel wellbores while the second one used a vertical injector which was perforated near
the top of the model Figure 2-1 displays both schemes [6]
Figure 2-1 Chung and Butler Well Schemes [6]
Chan conducted a set of numerical simulations including the standard SAGD well
configuration as displayed in Figure 2-2A He captured additional recovery up to 10-15
in offsetting the producer from injector The staggered well pattern provided the best
results within all the proposed configurations in terms of RF Increasing drawdown or
fluid withdrawal rate could also enhance oil recovery of SAGD process under those
conditions [9]
Joshi studied the thermally aided gravity drainage process by laboratory experiments
He investigated SAGD performance for three different well configurations 1) a
horizontal well pair 2) a vertical injector and a horizontal producer and 3) a vertical well
pair Figure 2-2B presents the schematic of the well patterns The maximum oil recovery
27
was observed in the horizontal well pair It was also shown that certain vertical fracture
may help the gravity drainage process especially at the initial stage as the fracture gave
a higher OSR than the uniform pack [21]
Top of Formation
Conventional Offset Staggered
Injector
Producer
Base of Formation
Figure 2-2A Well Placement Schematic by Chan [9]
Figure 2-2B Joshirsquos well pattern [20]
Leibe and Butler applied vertical injectors for three types of production wells
vertical horizontal and planar horizontal Effect of well type steam pressure and oil
properties were studied [22]
Nasr et al [10] conducted a series of experimental well configuration optimization
Figure 2-3 displays a summary of their studied patterns Their objective was to combine
an existingnewly drilled vertical well with the new SAGD well-pairs The experiments
were conducted in a 2-D scaled visual model and total of 5 tests were achieved The
combined paired horizontal plus vertical well was able to sweep the entire model in fact
chamber was growing vertically and horizontally The vertical injector accelerated the
communication between injector and producer The RF was improved from 40 up to
28
60 In addition they showed that for a fixed length of horizontal injector the longer
producer would show better performance [10]
Figure 2-3 Nasrrsquos Proposed Well Patterns [10]
The main goal of the industry has been to reduce the cost of SAGD operations which
drives the need to create and test new well patterns The Single well SAGD was
introduced to use a single horizontal well for both injection and production Figure 2-4
display the SW-SAGD well pattern It was field tested primarily at Cold Lake area Later
on several studies were conducted to investigate and optimize SW-SAGD [23] Luft et al
[24] improved the process by introducing insulated concentric coiled tubing (ICCT)
inside the well which would reduce the heat losses and was able to deliver high quality
steam at the toe of the well Falk et al [25] reviewed the success and feasibility of SW-
SAGD and confirmed ICCT development They reported the key pilot parameters and
reviewed the early production data
Polikar et al [26] proposed a new theoretical configuration called Fast-SAGD An
offset well with the depth and length as the producer was horizontally drilled 50 meters
away from the producer The offset single well is operated under Cyclic Steam
Stimulation mode They found that the offset well would precipitate the chamber growth
and increases the ultimate recovery factor
Shin and Polikar [27] focused on FAST-SAGD process and examined several more
patterns as displayed in Figure 2-5 They confirmed the enhancement of SAGD via
FAST-SAGD process In addition they demonstrated that addition of two offset wells on
29
either sides of a SAGD well-pair would enhance the total performance by increasing the
RF and decreasing the cSOR
Figure 2-4 SW-SAGD well configuration [23]
Figure 2-5 SAGD and FAST-SAGD well configuration [27]
Further investigation of the effects of well pattern was done by Ehlig-Economides
[28] Inverted multilevel and sandwiched SAGD were simulated for the Bachaquero
field in Venezuela (Figure 2-6) She included an extra producer in the new well schemes
of multilevel and sandwiched The idea was to utilize and optimize the heat transfer to the
reservoir The results showed that a large spacing between injector and producer is
beneficial and the available excess heat in the reservoir can be captured through extra
producer
30
Figure 2-6 Well Pattern Schematic by Ehlig-Economides [28]
Stalder introduced a well configuration called Cross-SAGD (XSAGD) for low
pressure SAGD The proposed pattern is displayed in Figure 2-7 The main idea is to
solve the limitation in oil drawdown due to steam trap control which originates from the
small spacing between injector and producer The injectors are located several meters
above the producers but they are perpendicular to each other The main concept behind
this well configuration is to move the injection and production point laterally once the
communication between injector and producer has been established In order to improve
the oil rate and obtain thermal efficiency the section of the wells close to the crossing
points requires to be either restricted from the beginning or needs to be plugged later on
The XSAGD results were much more promising at lower pressures [29]
Figure 2-7 The Cross-SAGD (XSAGD) Pattern [29]
31
Gates et al [30] proposed JAGD scheme for the reservoirs with vertical viscosity
variation The injector is a simple horizontal wellbore located at the top of the formation
but the producer is designed to be J-shaped to access all the reservoir heterogeneity They
proposed that the heel of the producer needs to be in vicinity of the base of the net pay
while the toe has to be several meters below the injectorrsquos toe Figure 2-8 displays the
JAGD well configuration schematic Initially the injector would be used for just cold
production thereafter it is converted to the thermal process while the cold production has
no more economical benefits Gates et al conducted a series of numerical simulations
and believed that the thermal efficiency of JAGD is beneficially higher than the normal
SAGD for the selected reservoirs
Figure 2-8 The JAGD Pattern [30]
In 2006 a SAGD pilot was started in Russia introducing a new well configuration
called U-shaped horizontal wells which is displayed in Figure 2-9 The pilot contained
three well pairs with the length of 200-400m The well pairs were drilled into the
formation primarily vertically down to the heel then followed the horizontal section and
eventually drilled up to the surface at the toe The vertical distance between the well pairs
is 5m It was shown that the U-Shaped wellbores will effectively displace the oil for the
complex reservoir with the SOR of 32 tt [31]
32
Figure 2-9 U-Shaped horizontal wells pattern [31]
Bashbush and Pina [32] designed Non-Parallel SAGD well pairs for the warm heavy
oil reservoirs Two cases with azimuth variation were compared against the basic SAGD
well configuration The first case named as Farthest Azimuthal in which the injector was
drilled upward from heel to toe The second case was called as Cross Azimuth in which
the heels of producer and injector are 6rsquo apart in one direction and the toes are 14rsquo apart
in the other direction Both cases are presented in Figure 2-10 Based on the presented
results none of the new patterns were able to improve the SAGD performance and the
recovery of basic SAGD was more impressive and successful
Figure 2-10 The Schematic of well patterns proposed by Bashbush and Pina [32]
Since the main objective of this study is to evaluate the effect of well configuration
on SAGD performance for three bitumen and heavy oil reserved of Alberta Athabasca
Cold Lake and Lloydminster it would be beneficial to review the existing pilot and
commercial SAGD projects in these reservoirs
33
22 Athabasca SAGD has been field tested in many successful pilots and subsequently through
several commercial projects in Athabasca-McMurray Formation Currently the number of
active SAGD pilot and commercial projects in Athabasca is quite large Figure 2-11
presents an overview of SAGD projects in Athabasca
The Underground Test Facility (UTF) was the first successful SAGD field test project
which was initiated by AOSTRA at 40 km northwest of Fort Mc-Murray [34 35] The
test consisted of multiple phases ldquoPhase Ardquo was meant to be just a case study to validate
the SAGD physical process ldquoPhase Brdquo was aimed at the commercial feasibility of
SAGD process ldquoPhase Drdquo tested horizontal drilling from surface which was not
completely successful The pilot was operated until 2004 with the ultimate recovery of
approximately 65 and cSOR of 24 m3m3 Since then SAGD has been applied in
various pilot and commercial projects in Athabasca
CENOVUS (Encana) is currently running the largest commercial SAGD project in
Canada The Foster Creek project started as a pilot with 4 well pairs in 1997 and then
expanded to 28 well-pairs in 2001 Currently it consists of more than 160 well pairs and
is producing over 100000 bbld The pay zone is located at 450 m depth and the target
formation is Wabiskaw-McMurray [36]
JACOS started its own SAGD project in Hangingstone using 2 well pairs in 1999 [37
38] Due to the success of primary pilot the project was expanded to 17 well pairs in
2008 Currently they are producing 10000 bbld The project is producing from
Wabiskaw-MacMurray which has 280-310 m depth [39]
One of the best existing SAGD project with respect to its cSOR appears to be the
MacKay River (currently owned by Suncor) with the average cumulative SOR of 25
m3m3 This project was started with 25 well pairs in 2002 steam circulation started in
September 2002 thereafter the production commenced in November 2002 Later 16
additional well pairs were added in 20052006 This project is also producing from
Wabiskaw-McMurray formation which is located 150m below the surface [40 41]
Encana (now CENOVUS) started a 6 well-pairs pilot SAGD at Phase-1 Christina
Lake in 20022003 Christina Lake has the lowest cSOR which is equal to 21 m3m3
34
Currently MEG Energy is also running SAGD at Christina Lake The net pay which is
Wabiskaw-McMurray is located at ~ 400m depth [42 43 and 44]
ConocoPhilips started their SAGD operation with a 3-well-pairs pilot project at
Surmont in 2004 Two of these well pairs contain 350 m long slotted liners while the
third well contains a 700 m long slotted liner The commercial SAGD at Surmont started
steam injection in June 2007 and oil production later on in Ocotber Currently Surmont is
operated by ConcoPhilips Canada on behalf of its 50 partner Total EampP Canada The
reservoir depth is ~400 m and the formation is Wabiskaw-McMurray [45 46 and 47]
Figure 2-11 Athabasca Oil Sandrsquos Projects [33]
Suncor is also a leader in SAGD operations currently running the Firebag with 40
well-pairs and the MacKay River project mentioned earlier The first steam injection in
the Firebag project commenced in September 2003 and the first oil production was in
January 2004 [48] The average daily bitumen production rate is 48400 bblday with the
cSOR of 314 m3m3 However the current capacity is 95000 bbld
The shallowest SAGD operation started in North Athabasca which had 90-100m
depth The Joslyn pilot project started with a well-pair and steam circulation in April
2004 While the Phase II of the project was ongoing a well blowout occurred in May
2006 Currently there is no injection-production in that area [49]
35
A 6535 joint venture of Nexen and OPTI Canada (now CNOOC Canada) phase 1 of
the Long Lake Project is the most unique SAGD project in Athabasca area The Long
Lake project is connected to an on-site upgrader The project involved three horizontal
well pairs at varied length from 800-1000 m 150 m well spacing Phase 1 of the project
is currently operational with a full capacity of 70000 bd operation that will extract crude
oil from 81 SAGD well-pairs and covert it into premium synthetic crude oil [50 51]
Devon started its Jackfish SAGD project in Athabasca drilling 24 well-pairs in 4 pads
in 2006 at a depth of 350m The target formation was Wabiskaw-McMurray First steam
injection commenced in 2007 The project capacity was designed for 35000 bbld
Currenlty the average cSOR is 24 m3m3 The second phase of Jackfish project
construction was started in 2008 and it is identical to the first phase of Jackfish 1 [52 53]
23 Cold Lake Cyclic Steam Stimulation (CSS) is the main commercial thermal recovery method
employed in the Cold Lake area Currently the largest thermal project across Canada is
the CSS operated by Imperial Oil However CSS has its own limitations which point to
application of SAGD at Cold Lake More recently Steam-Assisted Gravity Drainage
(SAGD) has been field tested in number of pilot projects at Cold Lake
The first SAGD pilot at Cold Lake area was Wolf Lake project Amoco started the
project in 1993 by introducing one 825 m horizontal well-pair in Clearwater Formation
The high cSOR and low RF of first three years operation forced Amoco to change the
project into a CSS process [54 55]
Suncor proposed Burnt Lake SAGD project with the target zone of Clearwater
Formation in 1990 and the operation was started in 1996 Later Canadian Natural
Resources Limited (CNRL) acquired the operation of Burnt Lake in 2000 It consists of
three well-pairs of 700 -1000m well length The reported cSOR and RF till end of 2009
were 39 m3m3 and 479 respectively [55 56]
The Hilda Lake pilot SAGD project was commenced by BlackRock in 1997 Two
1000 m well-pairs were drilled in the Clearwater Formation The operation was acquired
by Shell in 2007 The cSOR and RF at the end of 2009 were 35 m3m3 and 35 [57]
36
Amoco started its second SAGD pilot project in 1998 in Cold Lake area The pilot
included just one well pair of 600 m length which was drilled in Clearwater Formation
The Pilot was on operation for two years and due to high cSOR and low RF of the project
was turned into a CSS process [54]
Orion is a commercial project located in Cold Lake area producing from Clearwater
Formations Shell has drilled total of 22 well pairs with the average well length of 750m
However only 21 of them are on steam The first steam injection commenced in 2008
The cSOR is high due to early time of the project and the reported RF is 6-7 [54]
Husky established its own commercial SAGD at Cold Lake where the drilling of 32
well-pairs was completed in second half of 2006 The well-pairs have approximately
700m length The Tucker project aimed at producing from Clearwater formation with a
depth of ~400m First steam injection was initiated in November 2006 Eight more well-
pairs were appended to the project in 2010 The cSOR to end of May 2010 was above 10
m3m3 while the RF is below 5 [58]
Although SAGD has been demonstrated to be technically successful and
economically viable questions remain regarding SAGD performance compared to CSS
A more comprehensive understanding of the parameters affecting SAGD performance in
the Cold Lake area is required Well configuration is one of the major factors which
require greater consideration for process optimization Nevertheless the only well
configuration that has been field tested is the standard 11 configuration
24 Lloydminster The Lloydminster area which is located in east-central Alberta and west-central
Saskatchewan contains huge quantities of heavy oil The reservoirs are mostly complex
and thin and comprise vast viscosity range The peculiar characteristics of the
Lloydminster deposits containing heavy oil make almost every single production
techniques such as primary waterflood CSS and steam-flood uneconomic and
inefficient In fact the highly viscous oil coupled with the fine-grained unconsolidated
sandstone reservoirs result in huge rates of sand production with oil Although these
techniques may work to some extend the recovery factors remain low (5 to 15) and
large volumes of oil are left unrecovered when these methods have been exhausted
37
Because of the large quantities of sand production many of these reservoirs end up with a
network of wormholes that makes most of the displacement type enhanced oil recovery
techniques unsuitable Among the applicable methods in Lloydminster area SAGD has
not received adequate attention
Huskys Aberfeldy steam drive pilot started in February 1981 with 43 well drills out
of which 7 wells were for steam injection The pilot was on primary production for a
couple of years and the target zone was the Sparky Sands at 520m depth [59]
CSS thermal recovery at Lloydminster began in 1981 when Husky started the Pikes
Peak project It developed the Waseka sand at the depth of 500 meters which is a fairly
thick sand of higher than 10m pay The project initially consisted of 11 producing wells
In 1984 the project was altered into steamflood since the inter-well communication was
established Later on up to 2007 the project was expanded to 239 wells including 5
SAGD well-pairs The project has become mature with the recovery factor of around 70
percent [59 60]
The North Tangleflags reservoir contains fairly thick Lloydminster channel sand
(about 30 meters thick) The reservoir quality including porosity permeability and oil
saturation can be considered as superior Despite the encouraging initial oil rate primary
production failed due to the high viscosity oil of 10000 cp and water encroachment from
the underlying bottom water While the aquifer is only 5 metres compared to the oil zone
thickness of 30 metres the aquifer is quite strong and dominates primary production
performance limiting primary recovery to only a few percent In 1987 the operator
Sceptre Resources constructed a SAGD pilot which included four vertical injectors and a
horizontal producer The steam injection inhibits water encroachment as well as reducing
oil viscosity and this resulted in high recovery factor and low steam oil ratio In 1990 a
new horizontal well was added and performed the same manner as the existing one The
production well-pairs established an oil rate of as high as 200 m3d [61]
The Senlac SAGD project was initiated in 1996 with Phase A which consisted of
three 500m well pairs It is located 100 kilometers south of Lloydminster Alberta
Canada The target zone is the highly permeable channel sand of DinaCummings
formation buried 750 m deep Like other formations in the Lloydminster area the pay
zone is located above a layer of water In 1997 an extra 450 m well-pair was added to the
38
pilot Phase B was started in 1999 using three 500m well-pairs The vertical and
horizontal distance of the well-pairs is 5m and 135m respectively Later on Phase C
including two 750m of well-pairs was started up [62]
CHAPTER 3
GEOLOGICAL DESCRIPTION
40
31 Introduction Canada has the third largest hydrocarbon reserves after Venezuela and Saudi Arabia
containing 175 billion barrels of bitumenheavy oilcrude oil Currently the industry
extracts around 149 million barrels of bitumen per day [63] Figure 3-1 displays a review
of the bitumen resources and their basic reservoir properties
Figure 3-1 Albertarsquos bitumen resources estimate volume as of December 31 2011 [64]
The huge reserves of bitumen and heavy oil in Alberta are found in variety of
complex reservoirs The proper selection of an in-situ recovery method which would be
suitable for a specific reservoir requires an accurate reservoir description and
understanding of the geological setting of the reservoir In fact a good understanding of
the geology is essential for overcoming the challenges and technological difficulties
associated with in-situ oil sands development
Alberta has several types of hydrocarbon reserves but the major bitumen and heavy
oil deposits are Athabasca Cold Lake Peace River and Lloydminster Figure 3-2
displays the location of the extensive bitumen and heavy oil reservoirs across Alberta and
41
Saskatchewan The main deposits are in the Lower Cretaceous Mannville Group which is
found running from Northeastern Alberta to Southwest Saskatchewan
Figure 3-2 Bitumen and Heavy Oil deposit of Canada [65]
In this chapter a brief review of the geological description associated with the three
major oil sand and heavy oil reservoirs of Athabasca Cold Lake and Lloydminster is
presented
32 Athabasca This section of the geology study covers the Athabasca Wabiskaw-McMurray oil
sands deposit
Athabasca oil sands deposit is the largest petroleum accumulation in the world
covering an area of about 46000 km2 [66] In the Athabasca oil sand most of the
bitumen deposits are found within a single contiguous reservoir the lower cretaceous
McMurray-Wabiskaw interval Albertarsquos oil sands are early Cretaceous in age which
means that the sands that contain the bitumen were originally laid down about 100
million years ago [67] The McMurray-Wabiskaw stratigraphic interval contains a
significant quantity (up to 55) of the provincersquos oil sands resources Extensively drilled
studied and undergoing multi-billion dollar development the geology of this reservoir is
well understood in general but still delivers geological surprises
42
Both stratigraphic and structural elements are engaged in the trapping mechanisms of
Athabasca deposit The McMurray formation was deposited on the Devonian limestone
surface in a north-south depression trend along the eastern margin of the Athabasca oil-
sands area There is a structural dome in the Athabasca area which resulted from the
regional dip of the formation to the west and the salt collapse in the east [68] As
displayed in Figure 3-3 most of the reserves in Athabasca area are located east of this
anticline feature
Figure 3-3 Distribution of pay zone on eastern margin of Athabasca [69]
The thickest bitumen within the Athabasca McMurray-Wabiskaw deposit is generally
located in a northndashsouth trending channel complex along the eastern portion of the
Athabasca area Figure 3-4 displays the pay thickness of McMurray-Wabiskaw in
Athabasca area This bitumen trend contains all existing and proposed SAGD projects in
the Athabasca Oil Sands Area Outside the area the McMurray-Wabiskaw deposit
43
typically becomes thinner channel sequences are less predominant and the bitumen is
generally not believed to be exploitable using SAGD or reasonably predictable thermal
technologies Within the area of concern there is approximately 500 billion barrels of
bitumen in-place in the McMurray-Wabiskaw
Figure 3-4 Pay thickness of McMurray-Wabiskaw in the Athabasca Area [64]
As mentioned earlier currently there are two available commercial production
methods for the exploitation of bitumen out of McMurray-Wabiskaw Formations either
open-pit mining or in-situ methods The surface mining is able to extract approximately
10 percent of the reserves and mostly from the reserves situated along the valley of the
Athabasca River north of Fort McMurray The Cretaceous Formation in Athabasca River
has been eroded in a way that the oil sands are exposed in vicinity of the surface and
provide access for the shovel and trucks Figure 3-5 displays the cross view of the
Cretaceous Formation in Athabasca River The rest of the reserves are situated too deep
44
to provide access for the surface mining facilities and their recovery requires in-situ
methods However there are some deposits with a buried depth of 80-150m that are too
deep for surface mining and too shallow for steam injection
Figure 3-5 Athabasca cross section [69]
There is no official and formal classification for the stratigraphic nomenclature of the
Athabasca deposit however it has been developed based on experience Generally the
geologists divide the McMurray formation into three categories of Lower Middle and
Upper members This simple scheme may be valid on a small scale but when extended to
a broader scale may no longer apply [70] This historical nomenclature fails in some part
of the McMurray Formation In some areas McMurray Formation just includes lower
and upper members while in other parts of McMurray only middle and upper members
exist
The McMurray Formation is overlain by the Wabiskaw member of the Clearwater
Formation which is dominantly marine shale and sandstone The Clearwater itself is
located underneath the Grand Rapids Formation which is dominated by sandstone
Clearwater Formation acts as the cap rock for the McMurray reservoirs which prevents
45
any fluid flow from McMurray formation to its overlaying formation or ground surface
The thickness of Clearwater formation varies between 15 to 150m [71] The thickness
and integrity of Clearwater formation is essential since it must be able to hold the steam
pressure during the in-situ recovery operations However for the part of Athabasca where
the oil sand is shallow or the cap rock has low thickness special operating design such as
pressure and steam temperature is required
Figure 3-3 displays a summarized description of the facies characteristics through the
McMurray-Wabiskaw interval The McMurray Formation is located on top of the
Devonian Formation which is mostly shale and limestone
Age Group Wabasca Athabasca
Grand Rapids Grand Rapids
Clearwater ClearwaterU
pperM
annville Wabiskaw Wabiskaw
Lower C
retaceous
Lower
Mannville
McMurray McMurray
Mainly Sand Bitumen Saturated Sand
Figure 3-6 Correlation chart of Lower Cretaceous bitumen deposits at Athabasca Oil Sand
The Lower McMurray has good petro-physical properties it has high porosity and
permeability It mostly contains the bottom water in Athabasca area but in some specific
regions it comprises sand-dominated channel-and-bar complexes [69] The maximum
thickness of this member is up to 75m which is composed of mostly water-bearing sand
and is located above a layer of shale and coal The grain size in the lower member is
coarser than the other two members [68 72]
46
The Middle Member may have 15-30 m of rich oil-bearing sand and in some specific
areas it can even be up to 35 m Thin shale breaks are present while coal zone is absent in
the Middle McMurray The interface of Lower and Middle member is somewhere sharp
but it can be gradual as well In some specific areas of Athabasca the Middle member
channels penetrated into the Lower McMurray sediments deeply The upward-fining in
the Middle Member is typical [68 72]
The richest bitumen reserve among Athabasca deposit belongs to the Upper
McMurray member The Upper McMurrayrsquos channel sand thickness may be as high as 60
m with no lateral widespread shale discontinuity [69] This member is overlain by
Wabiskaw member of the Clearwater Formation Thin coal bioturbated sediments very
fine-grained and small upward coarsening sequences are typical in the Upper Member
[68] The Upper McMurray has somewhat lower porosity reduced permeability
compared to Lower McMurray The successful pilot and commercial schemes within the
Upper McMurray include the Dover UTF MacKay River Hangingstone and Christina
Lake
The Athabasca sands is comprise of approximately 95 quartz grains 2 to 3
feldspar grains and the rest is mostly clay and other minerals [67] The Athabasca sands
are very fine to fine-grained and moderately well sorted Shale beds within the oil sands
consist of silt and clay-sized material and only rarely contain significant amounts of oil
Less than 10 percent of the fines fraction is clay minerals [69] Low clay content and lack
of swelling clays differentiates it from other deposits in Alberta [68]
The McMurray Formation mostly occurs at the depths of 0 to 500 m The Athabasca
oil sands deposit is extremely heterogeneous with respect to physical reservoir
characteristics such as geometry component distribution porosity permeability etc
Several factors affect the petro-physical properties in Athabasca area and are attributed to
high porosity and permeability of McMurray Formation compared to the other sandstones
deposits minimum sediment burial early oil migration lack of mineral cement in the oil
sands which occupies the void space in porous media The petro-physical properties of
Athabasca are thought to have resulted from the depositional history of the sediments
However the bitumen properties are strongly affected by post depositional factors [71]
The reservoir and bitumen properties have a distinctive lateral and vertical variation It is
47
believed that the microbial degradations had a major effect on bitumen heterogeneity
across the Athabasca which resulted in heavier petroleum with accompanying methane as
a side product At reservoir temperature (11 degC) bitumen is highly viscous and immobile
The bitumen density varies from 6 to 11ordm API with a viscosity higher than 1000000 cP
Viscosity can vary by an order of magnitude over 50 m vertical span and 1 km lateral
distance
The single most fortunate characteristic feature of the Alberta oil sands is that the
grains are strongly water-wet However lack of this characteristic would not allow the
hot watersteam extraction process to work well
There are areas where basal aquifer with thickness of greater than 1 m are expected
however due to existence of an impermeable layer the oil-bearing zone is not always in
direct contact with bottom water [69]
33 Cold Lake The Cold Lake oil-sands deposit has been recognized as a highly petroliferous region
covering approximately 23800 km2 in east-central Alberta and containing over 250
billion barrels of bitumen in place it has the second highest rank for volume of reservesshy
in-place among the major oil sand areas in Canada [64] The bitumen and heavy oil
reserves at the Cold Lake area are contained in various sands of the Mannville Group of
Lower Cretaceous age Figure 3-7 and 3-8 present the correlation chart for Lower
Cretaceous bitumen and heavy oil deposits at Cold Lake area
As displayed on Figure 3-7 Cold Lake is inimitable in comparison with Athabasca
deposit all the formations in Mannville Group are oil bearing zones For this reason the
Cold Lake area provides an ideal condition for various recovery method applications
At Cold Lake the Mannville Group comprises the Grand Rapids Clearwater and
McMurray Formations Unlike the Athabasca Oil Sands more reserves belong to the
Grand Rapids and Clearwater Formations than the McMurray Currently the main target
of industry at Cold Lake area is Clearwater Formation Although the Grand Rapids has
higher saturation it is considered a future prospective target zone The Mannville Group
is overlain by the marine shale of the Colorado Group [73] At Cold Lake area the
48
Mannville sands are unconsolidated and the reservoir properties vary significantly over
the areal extension
Figure 3-7 Oil Sands at Cold Lake area [73]
Age Group Cold Lake Athabasca
Grand Rapids Grand Rapids
Clearwater
Upper M
annville Clearwater Wabiskaw
Lower C
retaceous
Lower M
annville
McMurray McMurray
Mainly Sand Bitumen Saturated Sand Shale
Figure 3-8 Correlation chart of Lower Cretaceous at Cold Lake area
49
The Clearwater is an unconsolidated and oil-bearing formation It is located on top of
the McMurray section The Clearwater is overlain by the Lower and Upper Grand Rapids
Formation which extends to the top of the Manville Group The Formation quality is
moderate and the thickness can be as high as 50 m [73] At Clearwater Formation only
about 20 of the sand is quatz The rest is feldspar (~28) volcanics (23) chert
(~20) and the rest is other minerologies [74 75 and 76] The reservoir continuity in
horizontal direction is considered excellent but on the other hand there is vertical
discontinuity in the forms of shale and tight cemented sands and siltstones which occurs
irregularly There are also many calcite concretions present The petro-physical properties
are considered excellent with the average porosity being 30 to 35 and the average
permeability in the order of multiple Darcies [75 77] Figure 3-9 displays the cross
section of Clearwater Formation at Cold Lake area and the extension trend of the reserves
in Alberta
In contrast to the massive sands of the Clearwater Formation the oil bearing zone in
the upper and lower members of the Grand Rapids Formation are thin and poorly
developed [75] In the Grand Rapids heavy oil can be associated with both gas and
water The gas can exist in forms of solution gas and gas cap Mostly the Upper Grand
Rapids has high gas saturations and acts as the overlaying gas cap formation
Fig 3-9 Clearwater Formation at Cold Lake area [75]
50
In the lower member of the Grand Rapids Formation reservoirs contain thin sands
with the interbedded shale the sands thickness ranges from 4-7 m but at some specific
zones the formation can be as thick as 15m The bed continuity is in sheet form and
considered as good but existence of occasional shale leads to poor reservoir continuity
The Lower Grand Rapid Formation has a fairly good continuity in both vertical and
horizontal directions Reservoir sands are fine to medium-grained and well sorted
Porosity can be as high as 35 while the permeability is in multi-Darcy range [78]
Figure 3-10 demonstrates the extension and cross plot of Lower Grand Rapids Formation
in Cold Lake area The lower Grand Rapids Formation is saturated with higher viscosity
bitumen and the solution gas is much lower than the Clearwater Formation [76] This
makes the Lower Grand Rapids a less desirable target zone for thermal applications
Another critical issue is that the formation is in contact with the water bearing sands The
Lower Grand Rapids formation has had a history of sand production problems due to its
highly unconsolidated nature
Fig 3-10 Lower Grand Rapids Formation at Cold Lake area [74]
In the upper member of the Grand Rapids Formation reservoirs consist of mostly gas
but in some regions the formation has oil bearing zone with the interbedded shale layers
The reservoirs are discontinuous with the average thickness of 6m Shale layer interbeds
are typical The sands are poorly to well sorted with a fine to medium grain size Porosity
51
is less than 35 and permeability is generally poor due to high silt and clay content
[75] Figure 3-11 displays the cross section of the Upper Grand Rapids Formation
The McMurray Formation at Cold Lake area has basal sand section upper zone of
thinner sand and interbedded shale layers The upper zone is generally oil-bearing sands
while the basal sand is mostly water saturated zone [74] Therefore the formation is
formed of couple of single pay zones which offers the possibility of multi-zone
completion The McMurray Formation at Cold Lake area is over a layer of aquifer The
deposit is fairly thin with the maximum thickness of 9m The lateral continuity of the
formation is fairly good but the vertical communication suffers from interbedded shale
layers The sands are fine to medium grain size and moderately well sorted The average
porosity is 35 which implies good permeability [75] Figure 3-12 presents the cross
view of the McMurray Formation at Cold Lake area
Fig 3-11 Upper Grand Rapids Formation at Cold Lake area [75]
52
Fig 3-12 McMurray Formation at Cold Lake area [75]
Most of Cold Lake thermal commercial operational target is Clearwater Formation
which is mostly at the depth of about 450 m The minimum depth to the first oil sand in
Cold Lake area is ~300m Grand Rapids Formation is a secondary thermal reservoir At
Clearwater the sands are thick often greater than 40m with a high netgross thickness
ratio Porosity ranges from 30 to 35 with oil saturations that average 70 PV At the
initial reservoir temperature of 13 degC the oil viscosity is about 100000 cp It is ordinary
to find layers of mud interbeds shale and clasts in Clearwater Formation Existence of
any clays or mud interbeds tends to significantly reduce the porosity of sediments and
consequently reducing permeability [77] The major issue in SAGD application in Cold
Lake area is the presence of heterogeneities of various forms
Generally the net pay at Cold Lake area is higher than the one in Athabasca On the
other hand Cold Lake reservoirs contain lower viscosity lower permeability higher
shale percentage lower oil saturation and extensive gas over bitumen layers
The main production mechanism in Cold Lake area is Cyclic Steam Stimulation
which has been the proven commercial recovery method since 1980rsquos Steam is injected
above formation fracture pressure and fractures are normally vertical oriented in a northshy
east to southwest direction However the CSS process has various geological and
operational limitations which make its applications so limited Unlike the CSS process
this area is in its in infancy for the SAGD applications Due to specific Cold Lake
53
reservoir properties SAGD method was less attractive here than in Athabasca A limited
number of SAGD projects have been field tested in the Lower Grand Rapids and
Clearwater Formations at Cold Lake area The Burnt Lake (Shell) and Hilda Lake
(Husky) were designed to produce bitumen from the Clearwater formation via the SAGD
process Later on since CSS had discouraging results at Lower Grand Rapids in the Wolf
Lake area due to extensive sand production BP and CNRL replaced CSS with the
SAGD The results demonstrated promising behaviour
34 Lloydminster Large quantity of heavy oil resources are present in variety of complex thin reservoirs
in Lloydminster area which are situated in east-central Alberta and west-central
Saskatchewan The area has long been the focal point of heavy oil development Figure
3-13 displays the latitude of Lloydminster area The whole area covers about 324
townships or 29 860 km2 [80] The Lloydminster heavy oil sands are contained in the
Mannville Group sediments which are early Cretaceous in age The Lower Cretaceous
contains both bitumen and heavy oil and has a discontinuous north-south trend which
starts from Athabasca in the north passes through Cold Lake and ends up in the
Lloydminster area [81]
At Lloydminster the entire Mannville Group is considered a target zone Which is
completely different from that which was characterized in Central Alberta In the
Lloydminster area interbedded sandstones with layers of shale and mudstones are
overlain by coals which occur repeatedly throughout the entire Mannvile Group [82 83]
Thus the Mannville Group is a complex amalgamation sandstone siltstone shale and
coal which are overlain by the marine shale sands of Colorado Group [80] The
sandstones are mostly unconsolidated with porous cross-beddings The shale is generally
bioturbated with a gray color which has acted as a hydrocarbon source rock [83]
In the Lloydminster area the Mannville Group can be subdivided into groups of the
Lower Middle and Upper members Each member informally comprises a number of
formations Different stratigraphic nomenclatures have been used in the Lloydminster
heavy oil area A summary of different subdivisions for the Mannville Group is presented
in Figure 3-14
54
Figure 3-13 Location of Lloydminster area [80]
There are some discrepancies in subdivision of the Mannville Group members
because of drastic lateral changes in facies Some geologists assign only Dina formation
to the lower Mannville while others include Lloydminster and Cummings Formations as
well In this research the stratigraphic nomenclature which is presented on Figure 3-14
has been considered As displayed on Figure 3-14 the Mannville group at Lloydminster
area is subdivided into nine stratigraphic units
The Lower Mannville contains Dina Formation which is formed of thick and blocky
sandstone Its thickness can reach as high as 67 m A layer of thick coal is located on top
of Dina This is the thickest coal in Manville Group at Lloydminster area which can be up
to 4m thick
55
Age Group Cold Lake Lloydminster
Colony
McLaren
Waseca U
pperGrand Rapids
Clearwater
Sparky
GP
RL-Rex
Lloydminster
Cummings
Middle
Lower C
retaceous
Mannville G
roup
McMurray Dina
Low
er
Mainly Sand
Heavy Oil Saturated Sand
Shale
Figure 3-14 Correlation chart of Lower Cretaceous at Lloydminster area
The Dina Formation is corresponding to the McMurray Formation in the Lower
Mannville Group of the Northern and Central Alberta basin [81] It is both oil and a gas
bearing zone but due to small reserve is not considered as a productive zone [84] The
sandstones are fine to medium-grained size and mainly well-sorted with some layers of
coal and shale
The Middle Mannville consists of five distinct members Cummings Lloydminster
RL-Rex General Petroleum (GP) and the Sparky This member is comprised of narrow
Ribbon-Shaped sandstone and shale layers [80] The associated thickness for each single
formation is approximately 6-9m and their range in width is about 16-64 km and in
length is 15-32 km [85]
The Sparky sandstone is very fine to fine-grained well sorted coarsening upward
with cycles of interbedded shale A thin coaly unit or highly carbonaceous mudstone is
usually present right at the top of Sparky unit [82] The Sparky Member might have a
thickness of up to 30m and usually with a 1m to 2m of mudstone The length of the
56
channel sand could extend in order of tens of kilometers while its width would be in
range of 03-2 km The water saturation in higher part of the Sparky is about 20 percent
whilst due to a transition zone in the lower part of Sparky the water saturation increases
as high as 60 percent [85] The permeability of the Sparky formation ranges between 500
to 2000 mD
GP Member with the maximum thickness of up to 18m thick (Average net pay of 6m)
is located beneath the Sparky member and has a fairly constant recognizable thickness
[86] The sands of GP are mostly oil saturated very fine-grained and well sorted A layer
of shale is situated beneath the oil stained sands of GP The clean sand porosity of the GP
usually exceeds 30 GP is less productive than Sparky
Rex Member can not be counted as a good pay among the Middle Mannvile Group It
included series of shale layers near the base of the formation and coal at the top Its
thickness may vary from 15-24m [87]
The Lloydminster is the most similar to the GP in terms of thickness and distribution
It consists of shale layers which are mostly gray with the very fine to fine grained sands
Thin layer of coal exists near the top of Lloydminster Formation The sands are mostly
oil stained but have high water saturation as well
The Cummings Member has a thickness of 12-48m containing highly interbedded
light gray shale Like the other members at Middle Mannville the sandstone is ribbon
shaped and mostly sheet sand stone (several tens of km2) [80] It has both oil and gas
saturations but it is not considered as commercially productive
Figure 3-15 clearly presents the distribution of Ribbon-Shaped Mannville group
57
Figure 3-15 Distribution of Ribbon-Shaped Manville Group at Lloydminster area [80]
The Upper Mannville comprises Colony McLaren and Waseca Formation This zone
has the same sandstone distribution as in the Middle Mannville The sandstones are
discontinuous and sheet-like which have variable thickness and width but mostly in the
range of 35 m and 300 m respectively [80] Variable successions of coal layers are
present throughout the Upper Member The Upper Mannville has both oil and gas zones
but the gas zone is situated in Alberta while the oil bearing horizons are mostly in the
Saskatchewan side [87]
The Colony and McLaren are usually difficult to differentiate Both are comprised of
fine to very fine grained sandstone with the interbedded light gray shale and variable coal
sequences [86 88] Their thickness can be as high as 61m while 6 m of that could be
shale or coal The oil and gas saturations are not commonly distributed over the entire
area but these formations are mostly gas stained However some local oil or gas stained
deposits can be found as well
Waseca Formation follows the same trend as the members of Middle Mannville
Group It consists of two pays with the thickness of 3-6m which is separated by 1m thick
58
interbedded shale layer [87] The lower part of Waseca Formation is oil saturated zone
and has high quality with porosity of ranging from 30-35 and permeability of 5-10
Darcyrsquos
In the Lloydminster area the target formations have quite a range and unlike the
Athabasca and Cold Lake area there is no specific and single pay for the current and
future developments However most of the Mannville Group formations are situated at
depth of about 450-500 m
The conventional oil ranges from heavy (lt15deg API) to medium gravity (up to 38deg
API) at reservoir temperature The Mannville Group sands in general have quite a large
range of the viscosity the crude oil viscosity ranges from 500 to 20000 cp at reservoir
temperature of 22 degC Water saturation varies between 10 to 20 percent The porosity and
permeability of most formations in Mannville Groups are 22-32 percent and 500-5000
mD respectively The rocks are mostly water wet but in some specific areas they can be
oil wet as well
The recovery mechanism in the study area is mostly primary depletion which is
principally by solution gas drive and gas cap expansion The primary recovery has a low
efficiency of about 8 due to high crude oil viscosity low solution GOR and low initial
reservoir pressure At the same time due to bottom water encroaching high water cuts
can be observed as well However numerous primary and secondary (mostly water-
flood) projects are being implemented in the area Figure 3-16 presents various active
projects in the Lloydminster area
The reservoirs are mostly complex and thin with a wide range of oil viscosity These
characteristics of the Lloydminster reservoirs make most production techniques such as
primary depletion waterflood CSS and steamflood relatively inefficient The highly
viscous oil coupled with the fine-grained unconsolidated sandstone reservoir often
result in huge rates of sand production with oil during primary depletion Although these
techniques may work to some extent the recovery factors remain low (5 to 15) and
large volumes of oil are left unrecovered when these methods have been exhausted
Because of the large quantities of sand production many of these reservoirs end up
with a network of wormholes which make most of the displacement type enhanced oil
recovery techniques inapplicable
59
For heavy oil reservoirs containing oil with the viscosity smaller than 5000 cp both
SAGD and steam-flooding can be considered applicable for extraction of the heavy oil
Minimum reservoir thickness of at least 15 meters is likely required for SAGD to be
applicable In fact this type of reservoir provides more flexibility in designing the thermal
recovery techniques as a result of their higher mobility and steam injectivity Steam can
be pushed and forced into the reservoir displacing the heavy oil and creating more space
for the chamber to grow There is considerable field experience available for developing
such techniques Aberfeldy steam drive pilot CSS thermal recovery at Pikes Peak North
Tangleflags SAGD pilot project and Senlac SAGD project
Figure 3-16 Lloydminster area oil field [89]
35 Heterogeneity The Albertarsquos oil sands deposits are extremely heterogeneous with respect to physical
reservoir characteristics and fluid properties Therefore the recovery methods which
depend on inter-well communication will suffer in Alberta deposits since the horizontal
continuity is commonly poor The reservoir heterogeneities have a deep impact in steam
chamber development and the ultimate recovery of SAGD In high quality reservoirs
60
which encounter no shale barrier or thief zones the classic SAGD chamber would be in
the form of inverted triangle pointing to the producer while for the poor quality reservoirs
the form of steam chamber is more elliptical than triangle and will be driven by
heterogeneities
The feasibility of SAGD field implementation depends on various reservoir
parameters such as reservoir geometry horizontal and vertical permeability depth net-
pay thickness bottom water overlaying gas cap existence of shale barriers component
distribution cap rock thickness viscosity of bitumen etc Detailed characterization of
above aspects is required to better understand the reservoir behaviour and reactivity at
production conditions SAGD performance depends directly on the presence or absence
of these factors
In controlling SAGD performance the following factors play critical roles
frac34 Horizontal continuity of cap rock
frac34 Ease of establishing an efficient communication between Injector and Producer
frac34 Presence of any heterogeneity across the net pay and their laterallongitudinal
extension
frac34 Extent of shale along the wellbore
frac34 Existence of bottom water or gas cap
frac34 Presence of lean zones (thief zones)
Both Lloydminster and Cold lake area have quite a thick and continuous cap rock laid
over the pay zones The horizontal continuity of cap rock within the McMurray
Formation is relatively poor and in some regions there is no cap rock at all and if shallow
enough the bitumen is extracted by surface mining
The shale heterogeneity is a minor issue at Athabasca while it creates serious
concerns at Cold Lake and Lloydminster area McMurray formation almost exhibits
analogous characteristics over the Athabasca region but some local heterogeneity also
exists There is no specific way to determine the extension of shale barriers in the oil
sands deposits The effect of shale presence on SAGD performance needs to be evaluated
through numerical simulations
In addition to the shale barriers and cap rock continuity water and gas zones have a
deep impact in steam chamber development and the ultimate recovery The bottom water
61
and gas cap thickness varies over few meters over the entire area of Alberta Their impact
on SAGD is variable and really depends on their thickness and extension over the entire
net pay In the McMurray less gas cap and bottom water exists while at Cold Lake and
Lloydminster and specifically at Lloydminster there are few formations which are not in
contact with gas or water zones
CHAPTER 4
EXPERIMENTAL EQUIPMENT AND
PROCEDURE
63
This chapter describes first the experimental equipment and second the experimental
procedures used to collect and analyse the data presented A consistent experimental
procedure was kept throughout the tests
The equipment description is presented in three sections a) viscosity and
permeability measurement equipment b) the equipment which comprised the physical
model setup and c) sample analysis apparatus
41 Experimental Apparatus The schematic of the SAGD physical model is presented in Figure 4-1
Steam
Water
Load Cell
Steam
Model Temperature
Figure 4-1 Schematic of Experimental Set-up
The model comprised several components including a) Steam Generator b) Data Acquisition
System c) Temperature Probes and d) Physical Model
411 3-D Physical Model
Physical models have been assisting the development of improved understanding of
complex processes where analytical and numerical solutions require numerous
simplifications During the past decades physical models have become a well-established
64
aid for improving the thermal recovery methods The physical models for studying
thermal recovery can be either in the form of partial (elemental) or fully scaled models
Due to the issues with respect to the handling operating and sampling of the thermal
projects usually elemental models have been incorporated to study the thermal processes
For the SAGD process the scaling criteria proposed by Butler were used in this study to
scale down the target reservoirs to the physical model size Butler analysed the
dimensional similarity problem in SAGD and found that a dimensionless number B3 as
given by the equation below must be the same in the field and the physical model [1]
kghB3 = αφΔSomυs
The dimensional analysis includes some approximations and simplifications as well
Some parameters were excluded from the above dimensional analysis and consequently
would be un-scaled between reservoir and physical model These parameters are rock-
fluid properties such as relative permeability and capillary pressure and thermal
expansion-compression emulsification effect and wellbore completion properties such
as skin and perforation zones
There are several additional discrepancies such as operating condition initial
bitumen viscosity and rock properties between the physical model and the field
Therefore to conduct a reasonable dimensional analysis a few assumptions concerning
the properties of the reservoir were considered which are listed in Table 4-1
Table 4-1 Dimensional analysis parameters field vs physical
Parameter Physical Model Athabasca Cold Lake m 19 39 39 Permeability D 300 3-5 3-5 Net pay m 025 20 20 micros cp ρ kgm3
70 987
30 1000
40 1000
φΔSo 04 02 02 Wellbore length m 05 500 500 Well-pair spacing m 05 200 200
According to economicalsimulation study conducted by Edmunds the minimum net
pay which can make a SAGD project feasible is 15m [90] So a thickness of 20m was
selected for both Cold Lake and Athabasca reservoirs The viscosity of saturating
65
bitumen at injecting steam temperature is different between the physical model and field
condition The thermal diffusivity α was assumed to be equal in physical model and the
field The permeability of the packing sand for the physical model is selected to make the
physical model dimensionally similar to the field As per Table 4-1 in order to establish
the dimensional similarity it is necessary to select high permeable packing sand for the
physical model comparing to the packing medium in field
The well length and well-pair spacing has no effect on B3 value but they impact the
physical model dimensions
The physical model designed for this study was a rectangular model which was
fabricated from a fiber reinforced phenolic resin with dimensions of 50macr50macr25 cm in i
j k directions The physical model is schematically shown in Figure 4-2 50 cm
Physical Model Cavity
25 cm
50 cm
Figure 4-2 Physical model Schematic
As a role of thumb the minimum well spacing is twice the net pay In designing the
current physical model the same rule was employed and the model width was selected as
50 cm The 50 cm well length is a minimal arbitrary value that was selected so that the
effect of well length on SAGD performance can be observed and at the same time the
total weight of model (the box 110 kg of sand and 25 liter of oil) would be reasonable
As shown in Figure 4-3 the model was mounted on a 15 m stand to facilitate its
handling Two mounting shafts were incorporated at the side of the model to enable
rotating the model by full 360 degrees
Most SAGD physical models described in the literature use one transparent side
which is usually made of Plexiglas Since this model is designed to account for the
longitudinal and lateral extension of chamber along a horizontal wellbore no visual side
66
was incorporated A total of 31 multi-point thermocouple probes each providing 5 point
measurements were installed to track the steam chamber within the model Figure 4-4
displays the location of the thermocouple probes in the model Thermocouples were
entered into the model from its back side and in 8 rows (A to G rows in Figure 4-4) Their
location was selected in a staggered pattern to cover the entire model The odd rows (A
C E and G) comprised 4 columns of thermocouples while the even rows (B D and F)
have 5 columns of thermocouples The thermocouples were connected to the Data
Acquisition instrument which provided the inputs for the LabView program to record
and display the temperature profile within the model
The pressure of the model is somewhat arbitrary It has an effect on the fluid
viscosity via its effect on the steam temperature but the scaling does not dictate any
pressure on the production side The model used in this work was designed for low
pressure operation and its rated maximum operating pressure was 100 kPa (gauge) The
maximum steam injection pressure used in the experiments was about 40 kPag
Figure 4-3 Physical Model
67
4
3 A B C D E F G
Figure 4-4 Thermocouple location in Physical Model
There are numerous reported studies of SAGD process using physical models but
most of them use two-dimensional models which ignore the effect of wellbore length in
the chamber development However since this model can be considered a semi-scaled 3shy
D model it is expected to provide more realistic and field representative results on the
effects of well configuration
412 Steam Generator
A large pressure cooker was modified to serve as the steam generator The pressure
cooker was made of heavy cast aluminum with the internal capacity of approximately 28
litres The vessels inside diameter was 126 inches the inside height was 14 inches and
its empty weight was 29 lbs
A frac12 inch line was connected to the opening for automatic pressure control which
eliminated the weight based pressure control During the experiments this outlet line was
connected to the injector well of the physical model Electrical heaters were installed in
the pressure cooker to heat the water and convert it to steam These electrical heaters
were controlled by a temperature controller that maintained the desired steam
temperature in the vessel In addition a pressure switch was installed in the power line
that would cut off the power to the heaters if the pressure became higher than the safe
limit Finally the pressure cooker also contained a rupture disc that would have relieved
the pressure if the internal pressure had become unsafe The selective pressure regulator
was designed to release excess steam at 18 lb of pressure The steam generator was
placed on top of a load cell to record the weight of the vessel and its contents The
decline in the weight provided a direct measure of the amount of steam injected into the
physical model
68
Figure 4-5 Pressure cooker
413 Temperature Probes
The temperature measurements inside the physical model were made with 31 multishy
point (5 points per probe) 18 inch diameter 23 inch length type-T thermocouples
Figure 4-5 presents the specification of the multi-point thermocouples
23rdquo
85rdquo
PTB
PTE
215rdquo
PTD
175rdquo
PTC
130rdquo
PTA40rdquo
Figure 4-6 Temperature Probe design
42 Data Acquisition A National Instruments data acquisition system was used to monitor and record the
experimental data These data included the temperatures sensed by a large number of
thermocouples in the experimental set-up as well as the weight of the steam generator A
LabVIEW program was used to coordinate the timing and recording of the data
43 RockFluid Property Measurements
431 Permeability measurement apparatus
A simple sand-pack apparatus was assembled to measure the permeability of the sand
used in the physical model experiments The apparatus comprised a low rate pump a
69
differential pressure transducer and a Plexiglass sand-pack holder (for high rates a
stainless steel holder was used) The schematic of the apparatus is displayed in Figure 4shy
7 The main objective was to inject water at specific rates and measure the corresponding
pressure difference across the sand pack The permeability was determined using Darcyrsquos
law since the length and diameter of the sand pack was known
24 cm 25 cm
Figure 4-7 Permeability measurement apparatus
432 HAAKE Roto Viscometer
The HAAKE RotoVisco 1 is a controlled rate (rotational) viscometer rheometer
which is specifically designed for quality control and viscosity measurements of fluids
such as liquid hydrocarbons It measures viscosity at defined shear rate or shear stress
The possible range of temperature that the HAAKE viscometer can handle is 5-85 ordmC
Figure 4-8 displays the front view of the HAAKE viscometer
The viscometer used in this work offered a choice of 3 sensor rotors Z31 Z38 and
Z41 which are designed for high middle and low viscosity fluids respectively The
amount of sample required for each sensor is different and the choice of sensor depends
primarily on the viscosity of the fluid The table 4-2 presents the specification for each
sensor
70
Figure 4-8 HAAKE viscometer
Table 4-2 Cylinder Sensor System in HAAKE viscometer
Senor Z31 Z38 Z41
Rotor
Material Titanium Titanium Titanium
Radius Ri mm 1572 1901 2071
+- ΔRi mm 0002 0004 0004
Length mm 55 55 55
+- L mm 003 003 003
Cup
Material Steel Steel Steel
Radius Ra mm 217 217 217
+- ΔRa mm 0004 0004 0004
Sample Volume cm3 520 330 140
71
433 Dean-Stark distillation apparatus
Two types of samples were obtained from each experiment 1) the samples which
were in the form of water in oil emulsions and 2) the water-oil-sand samples in the form
of core sample from the model For separation of water from oil and water and oil from
sand the extraction method which uses the Dean-Stark distillation method was
incorporated The Dean-Stark apparatus consists of a heating mantle round bottom flask
trap and condenser as shown in Figure 49
The sample was mixed with toluene with the proportion of 21 and was poured in the
flask The sample was heated with the heating mantle for 24 hours During the heating
vapors containing the water and toluene rise into the condenser where they condense on
the walls of the condenser Thereafter the liquid droplets drip into the distilling trap
Since toluene and water are immiscible they separate into two phases When the top
layer (which is toluene being less dense than water) reaches the level of the side-arm it
can flow back to the flask while the bottom layer (which is water) remains in the trap
After 24 hours no more water exists in the form of emulsion in oil It is important to drain
the water layer from the Dean-Stark apparatus as needed to maintain room for trapping
additional water
Since during each test up to 60 samples were collected a rack containing six units of
Dean-Stark distillation set-ups were employed to speed up the analysis These units were
located in a fume hood
Extraction of water and oil from oil-water-sand mixture was conducted in the same
Dean-Stark distillation apparatus with implementation of some minor changes A Soxhlet
was inserted on top of the flask The mixture of water-oil-sand was placed inside a
thimble which itself is placed inside the Soxhlet chamber The rest of process is the same
as the one expressed on Dean-Stark distillation process The sand extraction apparatus is
displayed on Figure 4-10
72
Figure 4-9 Dean-Stark distillation apparatus
Figure 4-10 Sand extraction apparatus
73
44 Experimental procedure Each experiment consisted of four major steps model preparation running the
experiment analysis of the produced samples cleaning
Prior to each experiment the load cell was calibrated to decrease the errors with
respect to weight measurement of the steam generator
441 Model Preparation
The model preparation was achieved in a step-wise manner as follows
bull Cleaning the physical model
bull Pressure testing the model
bull Packing the model
bull Evacuating the pore space of packed model
bull Saturating the model with water
bull Displacing the water with bitumen
Prior to each experiment the physical model was opened the thermocouples were
taken out and the whole set was cleaned Thereafter the model was assembled the
thermocouples were placed back into the model and the pressure test was conducted to
make sure there was no leak in the model Usually the model was left pressurized with
gas for 12 hrs to make sure there was no pressure leak
Various fittings were incorporated in the model for the purpose of packing bitumen
saturation and future well placement The ones for bitumen saturation had mesh on them
while the other ones were fully open
At the next stage the physical model was packed using clean silica sand During
packing the model was vibrated using a pneumatic shaker During the vibration the model
was held at several different angles to make sure that the packing was successful and no
gap would be left behind and a homogenous packing was created The packing and
shaking process typically took 48 hours of work and about 120 kg of sand was required to
fill the model
The next step was to evacuate the model to remove air from the pore space The
model was connected to a vacuum pump and evacuated for 12 hours The model was
disconnected from the vacuum pump and kept on vacuum for couple of hours to make
74
sure that it held the vacuum If high vacuum was maintained it was ready for saturating
with water
The model was saturated with de-ionized water using a transfer vessel The water
vessel was filled with water placed on a balance and was connected to the bottom of the
model Since the transfer vessel was placed at a higher level than the model both
pressure difference and gravity head forced the water to imbibe into the packed model
Approximately 21-22 kg water was required to fully saturate the model with water which
was equal to the total pore volume of the model The last stage is the drainage
displacement of water with the bitumen Two different bitumen samples were available
and both of them were practically immobile at room temperature The oil was placed in a
transfer vessel which was wrapped with the heating tapes and was connected to a
nitrogen vessel The oil was warmed up to 50-60 ordmC and was pushed into the model by
gravity and pressurized nitrogen The selected temperature was high enough that made
the bitumen mobile and was low enough to prevent evaporation of the residual water
Figure 4-11 displays bitumen saturation arrangement
A three point injection scheme was used with injection points at the top of the model
During the oil flood the injection points started at the far end and were moved to the
middle of the model after about 60 of the expected water production had occurred and
finally were directly on top of the production ports near the end of drainage The
displaced water was produced via three different valves and the relative amount of water
produced from the two outer valves was monitored and kept close to each other by
manipulating the openings of these TWO valves This ensured uniform bitumen
saturation throughout the model and specifically at the corners of the model The
displaced water was collected and the connate water and initial oil saturation were
calculated Approximately 18 kg of bitumen was placed in the model which took between
two to three weeks of bitumen injection
75
1
2
3
1 Pressure vessel wrapped with heating tapes
2 Isolated transfer line
3 Connection valves
Bitumen flow direction
Figure 4-11 Bitumen saturation step
442 SAGD Experiment
Each experiment was initiated by calibration of the load cell A few hours before
steam injection the steam generator was filled with de-ionized water step by step (by
adding weighed quantities of water) and the load cell reading was recorded
The steam generator was set to a desired temperature between 107-110 ordmC The steam
transfer line which connected the steam generator to the model was wrapped with heating
tape The purpose was to ensure that high quality steam would be injected into the model
and eliminate any steam condensation prior to the inlet point of the injector The weight
of the steam generator was recorded every minute
After the steam generator had reached the set point temperature the injection valve
was opened to let the steam flow into the model The production valve was opened
simultaneously The produced oil and water samples were collected in glass jars
76
Figure 4-12 InjectionProduction and sampling stage
The temperatures above the injection and production wells in the model were
continuously monitored via LabView program Once steam break-through occurred in the
production well steam trap control was achieved using back pressure via the production
valve This was confirmed by monitoring the temperature of the zone between producer
and injector and ensuring that an adequate sub-cool (approximately 10 ordmC) was present
The produced fluid sampling bottle was changed every 20-30 minutes and each
experiment took between 12 to 30 continuous hours to complete Figure 4-12 shows the
injectionproduction and sampling stage
At end of the test the steam injection was stopped but the production was continued
to get the amount of oil which could be produced from the stored heat energy in the
model Then the steam generator was shut off and the physical model was cooled down
After the model had completely cooled down the thermocouples were taken out in 3
steps and 27 samples of sands were taken from the model from three different layers in
the model Figure 4-13 displays the bottom view of the mature SAGD model and the
location of the sand samples in that layer
77
1 2 3
4 5 6
7 8 9
Figure 4-13 Bottom layer of the model after SAGD experiment and the sampling points for sand analysis
443 Analysing samples
Each sample bottle was weighed to obtain the weight of the produced sample The
sample analysis started with separation of water from oil in the Dean Stark set up Each
jarrsquos content was mixed with toluene and the whole mixture was placed in one single
flask 6 samples were analysed simultaneously using the six available Dean-Stark set ups
Each analysis took at least 12 hours During the extraction the collected water in the trap
part of the set up was drained as needed to allow more water to be collected in the trap
Once the separation was completed the total amount of water produced from the sample
was weighed and recorded The amount of oil produced was determined from the
difference between the total sample weight and the weight of water This procedure was
repeated for the all samples and eventually the cumulative oil and water production
profile could be determined This water-oil separation took about 10-15 days for each
experiment
The next step was separation of water and oil from the collected sand samples Since
only 4 Soxhlet units were available only four sets of separation could be run
78
simultaneously The mixture was placed in the thimble and weighed The thimble
containing the sand sample was placed in the Soxhlet chamber The evaporation and
condensation of toluene washes the water and oil from the sand and eventually they will
be condensed and the water collected in the trap Once the thimble and sand were clean
it was taken out and dried The amount of collected water was recorded and consequently
the residual oil and water saturations could be determined
444 Cleaning
At the end of each run the entire set up including the physical model the injector and
producer all fittings and valves and connection lines were disassembled The valves and
fittings were soaked in a bucket of toluene while the wells and the physical model were
washed with toluene
CHAPTER 5
NUMERICAL RESERVOIR SIMULATION
80
This chapter discusses the numerical simulation studies conducted to optimize the
well configuration in a SAGD process These numerical studies were focused on three
major reservoirs in Alberta as Athabasca Cold Lake and Lloydminster The description
of the simplified geological models associated with each reservoir is presented first
followed by the PVT data for each reservoir The results of simulation studies are then
presented and discussed
51 Athabasca
The McMurray formation mostly occurs at the depths of 0 to 500 m The total
McMurray formation gross thickness varies between 30-100 meters with an average of 30
m total pay The important petro-physical properties of McMurray formation are porosity
of 25ndash35 and 6-12 D permeability The bitumen density varies from 8 to 11ordm API with a
viscosity of larger than 1000000 cp at reservoir temperature of 11 degC
511 Reservoir Model
Numerical modeling was carried out using a commercial fully implicit thermal
reservoir simulator Computer Modeling Group (CMG) STARS 200913 A simplified
single well pair 3-D model was created for this study The model was set to be
homogenous with average reservoir and fluid properties of the McMurray formation
sands in Athabasca deposit Since the model is homogenous and the SAGD mechanism is
a symmetrical process only half of the SAGD pattern was simulated The model size was
30macr500macr20 m and it was represented with the Cartesian grid blocks of size 1macr50macr1 m
in imacrjmacrk directions respectively The total number of grid blocks equals 6000 Figure
5-1 displays a 3-D view of the reservoir model
Figure 5-2 shows that across the well pairs the size of the grid blocks are minimized
which allows capturing a reasonable shape of steam chamber across the well pairs In
addition since most of the sudden changes in reservoir and fluid temperature saturation
and pressure occurs in vicinity of the well-pairs using homogenized grid blocks across
the well-pairs allows the model to better simulate them
81
Figure 5-1 3-D schematic of Athabasca reservoir model
30 500
20
Figure 5-2 Cross view of the Athabasca reservoir model
Injector
Producer
The horizontal permeability and porosity was 5 D and 34 respectively and the
KvKh was set equal to 08 for all grid blocks The selected reservoir properties for the
representative Athabasca model are tabulated in table 5-1 The initial oil saturation was
assumed to be 85 with no gas cap above the oil bearing zone The thermal properties of
rock are provided in table 5-1 as well [91] The heat losses to over-burden and under-
burden are taken into account CMG-STARS calculate the heat losses to the cap rock and
base rock analytically
The capillary pressure was set to zero since at reservoir temperature the fluids are
immobile due to high viscosity and at steam temperature the interfacial tension between
82
oil and water becomes small Moreover the capillary pressure is expected to be very
small in high permeability sand
Table 5-1 Reservoir properties of model representing Athabasca reservoir
Net Pay 20 m Depth 250 m Permeability Kh 5000 md KvKh 08 Porosity 34 Initial Pressure PR 2000 kPa Initial Temperature TR 11 degC Oil Saturation So 85 mole fraction Gas in Oil 6 Oil Viscosity TR 16E+6 cp Formation Compressibility 14E-5 1kPa Rock Heat Capacity 26E+6 Jm3degC Thermal Rock Conductivity 66E+5 JmddegC OverburdenUnderburden Heat Capacity 26E+6 Jm3degC
512 Fluid Properties
Only three fluid components were included in the reservoir model as Bitumen water
and methane Three phases of oleic aqueous and gas exist in the model The oleic phase
can contain both bitumen and methane the aqueous phase contains only water while the
gas phase may consists of both steam and methane
The thermal properties of the fluid and rock were obtained from the published
literature The properties of the water in both aqueous and gas phase were set as the
default values of the CMG-STARS The properties of the fluid (Bitumen and methane)
model are provided in Table 5-2
Table 5-2 Fluid properties representing Athabasca Bitumen
Oil Viscosity TR 16E+6 cp Bitumen Density TR 9993 Kgm3
Bitumen Molecular Mass 5700 gmole Kv1 545 E+5 kPa Kv4 -87984 degC Kv5 -26599 degC
To represent the phase behavior of methane a compatible K-Value relationship was
implemented with the CMG software [92] The corresponding K-value for methane is
provided in table 5-2 [91] It is assumed that no evaporation occurs for the bitumen
component
83
Kv4Kv T + KvK minus Value = 1 exp 5
P
To estimate a full range of viscosity vs temperature the Mehrotra and Svercek
viscosity correlation was used [93]
ln ln (μ) = A + B ln (T) Figure 5-3 shows the viscosity-temperature variation for bitumen model
10
100
1000
10000
100000
1000000
10000000
100000000
Visc
osity
cp
00 500 1000 1500 2000 2500 3000
Temperature C
Figure 5-3 Temperature dependency of bitumen modelrsquos Viscosity for Athabasca
513 Rock-Fluid Properties
Since there was no available experimental data for the rock fluid properties the three
phase relative permeability defined by Stonersquos Model was used to combine water-oil and
liquid-gas relative permeability curves Two types of rock were defined in most of the
numerical models rock type 1 which applied to entire reservoir and rock type 2 which
was imposed on the wellbore but in both rock types the rock was considered water-wet
Straight line relative permeability was defined for the rock fluid interaction in the well
pairs
Some typical values of residual saturates were selected [91 47] and since this part of
study does not include any history matching procedure therefore all the end points are
84
equal to one Table 5-3 summarizes the rock-fluid properties The water-oil and gas-oil
relative permeability curves are displayed on Figure 5-4 Figure 5-5 presents the relative
permeability sets for the grid blocks containing the well pairs
Figure 5-4 Water-oil relative permeability
85
Figure 5-5 Relative permeability sets for DW well pairs
Table 5-3 Rock-fluid properties
SWCON Connate Water 015 SWCRIT Critical Water 015 SOIRW Irreducible Oil for Water-Oil Table 02 SORW Residual Oil for Water-Oil Table 02 SGCON Connate Gas 005 SGCRIT Critical Gas 005 KROCW - Kro at Connate Water 1 KRWIRO - Krw at Irreducible Oil 1 KRGCL - Krg at Connate Liquid 1 nw 3 now 3 nog 3 ng 2
514 Initial ConditionGeo-mechanics
The reservoir model top layer is located at a depth of 250 m and at initial temperature
of 11 ordmC The water saturation is at its critical value of 15 and the initial mole fraction
of gas in bitumen is 6 The total pore volume and oil phase volume are 128 and 109
E+5m3 Geo-mechanical effect was ignored in the entire study
515 Wellbore Model
CMG-STARS 200913 provides two different formulations for horizontal wellbore
modeling SourceSink (SS) approach and Discretized Wellbore (DW) model SS
modeling has some limitations such as a) the friction and heat loss along the horizontal
section is not taken into account b) it does not allow modeling of fluid circulation in
wellbores c) liquid hold-up in wellbore is neglected [94] In fact to heat up the
intervening bitumen between the well pairs during the preheating period of SAGD
process a line heater with specific constraint has to be assigned for the wellbore This
86
would affect the cumulative SOR The DW model provides the means to simulate the
circulation period and it considers both heat and friction loss along the horizontal section
of the wellbore
CMG-STARS models a DW the same as the reservoir Hence each wellbore segment
is treated as a grid block in which the fluid flow and heat transfer equations are solved at
each time step The flow in tubing and annulus is assumed as laminar The flow equations
through tubing and annulus are based on Hagen-Poiseuille equation If the flow became
turbulent then the permeability of tubing and annulus would be modified
However DW has its own limitations as well One of the most significant restrictions
of DW is that it does not model non-horizontal (deviated) wellbores For this study a
combination of both SS and DW models were used
Most of the rock fluid properties were also used for the grid blocks containing the
DW except the thermal conductivities and relative permeability The thermal
conductivity of stainless steel and cement were set for tubing and casing respectively
Straight line relative permeability presented in Figure 5-5 was imposed for the grid
blocks containing DW
All of the wells were modeled as DW except the non-horizontal ones The non-
horizontal injectors are modeled as line sourcesink combined with a line heater The line
heaters were shut in after the circulation period ended The DW consists of a tubing and
annulus which were defined as injector and producer respectively This would provide
the possibility of steam circulation during the preheating period
516 Wellbore Constraint
The injection well is constrained to operate at a maximum bottom hole pressure It
operates at 500 kPa above the reservoir pressure The steam quality is equal to 09 at the
sand-face The corresponding steam saturation temperature at the bottom-hole pressure is
224 degC
The production well is assumed to produce under two major constraints minimum
bottom-hole pressure of 2000 kPa and steam trap of 10 degC The specified steam trap
constraints for producer will not allow any live steam to be produced via the producer
87
517 Operating Period
SAGD process consists of three phases of a) Preheating (Start-up) b) Steam Injection
amp Oil Production and c) Wind down
Each numerical case was run for total of 6 years The preheating is variable between
1-4 months depending on the well configuration For the base case the circulation period
is 4 months which is similar to the current industrial operations The main production
periods is approximately 5 years while the wind down takes only 1 year The SAGD
process stops when the oil rate declines below 10 m3d
518 Well Configurations
Numerous simulations were conducted for well configuration cases in search for an
improved well configuration for the McMurray formation in Athabasca type of reservoir
To start with a base case which has the classic well pattern (11 ratio with 5 m vertical
inter-well spacing) was modeled The base case was compared with available analytical
solutions and performance criteria Furthermore the performance of the examined well
patterns was compared against the base case results
Figure 56 presents some of the modified well configurations that can be used in
SAGD operations These well configurations need to be matched with specific reservoir
characteristics for the optimum performance None of them would be applicable to all
reservoirs
5m
Injector
Producer
Injectors
Producer 5m
Injector
Producer
Basic Well Configuration Vertical Injectors Reversed Horizontal Injector Injectors
Producer
Injector
Producer
Inclined Injector Parallel Inclined Injectors Multi Lateral Producer
Figure 5-6 Schematic representation of various well configurations for Athabasca Reservoir
88
5181 Base Case
This configuration is the classic configuration as recommended by Butler It follows
the same schedule of preheating normal SAGD and wind down The vertical inter-well
distance was 5 m and the producer was placed 15 m above the base of the pay zone Two
distinct base cases were defined for comparison a) both injector and producer wellbores
were modeled based on DW approach b) the injector was modeled with SS wellbore
approach and the producer was simulated with DW Since in some of the future well
patterns the injectors is modeled as a Source well then for the sake of comparison case b
can be used as the base case
The circulation period is 4 month and the total production period is approximately 6
years The results of both cases are reasonable and close to each other Figures 5-7 and 5shy
8 present the oil rate and recovery factor vs time for both cases Figure 5-9 and 5-10
display the cSOR and chamber volume vs time
Both cases provided similar results except for the cSOR The recovery factor for both
DW and SS models are close to each other being 662 and 650 respectively As per
Figure 5-9 there is a small difference in cSOR values for the two base cases The final
cSOR for the Base Case-DW and Base Case-SS are 254 and 223 m3m3 respectively
On Figure 5-7 the total production period is divided into four distinct regions as 1)
circulation period 2) ramp-up 3) plateau and 4) wind down Figure 5-11 displays the
cross section of the chamber development across the well pairs during the four regions
By the time the ramp-up period is completed the chamber reaches the top of reservoir
The maximum oil rate occurs at the end of ramp-up period During this period the
chamber has the largest bitumen head and smallest chamber inclination
In the Base Case-SS model a line heater was introduced above the injector The
heater with the modified constraint injected sufficient heat into the zone between the
injector and producer This supplied amount of energy is not included in cSOR
calculations Also the SS wellbore does not include the frictional pressure drop along the
wellbore These conditions make the base case with the line source to operate at a lower
cSOR
89
Oil
Prod
Rat
e SC
TR (m
3da
y)
0
20
40
60
80
100 Base Case-DW Base Case-SS
1 2 3 4
SCTR stands for Sector
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-7 Oil Production Rate Base Case
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70
80 Base Case-DW Base Case-SS
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-8 Oil Recovery Factor Base Case
90
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-DW Base Case-SS
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-9 Cumulative Steam Oil Ratio (cSOR) Base Case
Stea
m C
ham
ber V
olum
e S
CTR
(m3)
0
10000
20000
30000
40000
50000
60000 Base Case-DW Base Case-SS
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-10 Steam Chamber Volume Base Case
91
1 2
3 4
Figure 5-11 Cross view of chamber development at 4 specified time frames Base Case
Stea
m Q
ualit
y D
ownh
ole
00
01
02
03
04
05
06
07
08
09
10
Base Case-DW Base Case-SS
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-12 Steam Quality of DW vs SS during the SAGD life period Base Case
92
Figure 5-12 displays the steam quality of DW vs SS injector for the base cases In the
model containing discretized wellbore there is some loss in steam quality due to the heat
loss and friction while in the SourceSink model the steam quality profile is completely
flat no change along the injector
Figure 5-13 displays the pressure profile along the vertical distance between the toe
of injector and producer and also the pressure profile at the heel of injector and producer
There is a small pressure drop along the injector andor producer It seems that the way
STARS treats producers and injectors is somewhat idealistic The producer drawdown
does not change from heel to the toe which in real field operation is not true Most of the
SAGD operators have problems in conveying the live steam to the toe of the injector to
form a uniform steam chamber Das reported that a disproportionate amount of steam
over 80 is injected near the heel of the injector and the remaining goes to the toe if live
steam conquers the heat loss and friction along the tubing [14] As a result the steam
chamber grows primarily at the heel and has a dome shape along the well pairs This
situation may lead to steam breakthrough around the heel area and reduce the final
recovery factor Since these effects are not captured in the model the simulated base-case
performance is better than what can be achieved in the field Therefore when the new
well configurations are compared against the base cases and show even marginally better
performance they are considered promising configurations
The base case model was validated against Butlerrsquos analytical model The analytical
model includes the solution for oil rates during the rising chamber and depletion period
[1] The parameters of the numerical model were incorporated into the analytical solution
and the obtained oil production rate was compared against the numerical base case result
Table 5-4 presents the list of parameters incorporated in the analytical solution of Base
Case results The oil production rate for numerical and analytical results is presented in
Figure 5-14 There is a reasonable consistency between both results Both models
forecast quite similar ramp up and maximum oil rate However after two years of
production the results deviate from each other which is due to the boundary effects and
the simplifying assumptions (single phase flow ignoring formation compressibility
constant viscosity etc) in the analytical solution In fact the numerical model is able to
93
simulate the wind down step as well while the analytical solution only predicts the
depletion period
Table 5-4 Analytical solution parameters
Typical Athabasca Base Case Reservoir Temperature 11
Oil Kinematic Viscosity TR 158728457 Bitumen Kinematic Viscosity 100degC 2039
Reservoir Thickness 20 Thermal Diffusivity 007
Porosity 034 Initial Oil Saturation 085
Residual Oil Saturation 025 Effective Permeability for Oil Flow 16
Well Spacing 60 Vertical Space From Bottom 15
Steam Pressure 25 Parameter m 3
Bitumen Kinematic Viscosity Ts 710E-06
degC cS cS m m2D
D m m Mpa
cS
Pres
sure
(kPa
)
2480
2482
2484
2486
2488
2490
2492
2494
2496
2498
2500
Injector Heel Injector Toe Producer Heel ProducerToe
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-13 Pressure Profile between Injector and Producer at the heel and toe Base Case
94
0
20
40
60
80
100
120
140
160
0 1 2 3 4 5 6 Time Year
Oil
Prod
uctio
n R
ate
m3 d
Butlers Analytical Method
CMG Simulation Results Base Case
Figure 5-14 Comparison of numerical and analytical solutions Base Case
Aherne and Maini introduced the Total Fluid to Steam Ratio (TFSR) which is an
indicator for evaluation of the balance between fluid withdrawal and steam injection
pressure [35] In fact the TFSR indicates the water leak off from the steam chamber The
TFSR was expressed as
H2O Prd + Oil Prd - Steam in ChamberTFSR = Steam Inj
They stated that if the TFSR is less than 138 m3m3 then the pressure of the reservoir
will increase or there will be some leak off from the chamber The current numerical base
case model has a TFSR of 14 m3m3 which demonstrates that the injection and
production is balanced
The base case was evaluated using these validation criteria Since its performance is
acceptable the performance of future well patterns will be compared against the base
case
5182 Vertical Inter-well Distance Optimization
The optimum vertical inter-well distance between the injector and producer depends
on reservoir permeability bitumen viscosity and preheating period Locating the injector
95
close enough to the producer would shorten the circulation period but on the other hand
the steam trap control becomes an issue To obtain the best RF and cSOR the vertical
distance needs to be optimized To study the effect of vertical inter-well distance on
SAGD performance five distances were considered 3 4 6 7 and 8m The idea was to
investigate if changing the vertical distance will improve the recovery factor and cSOR
The oil rate RF cSOR and the chamber volume are presented on Figures 5-15 5-16
5-17 and 5-18 respectively It is observed that the performance decreases as the vertical
distance increases above 6m Increasing the inter-well spacing between injector and
producer delays the thermal communication between producer and injector which
imposes longer circulation period and consequently higher cSOR Since for the large
vertical distance between the well pairs the injector is placed close to the overburden the
steam is exposed to the cap rock for a longer period of time and therefore the heat loss
increases which results to higher cSOR and less recovery factor When the inter-well
distance is smaller than the base case the preheating period is shortened but the effect on
subsequent performance is not dramatic The optimum vertical distance between the
injector and producer is assumed to be 5m in most of reservoir simulations and field
projects Figures 5-16 and 5-17 show that the vertical distance can be varied from 3 to 6m
and 4m appears to be the optimal distance The 4m vertical spacing has the highest
recovery factor and same cSOR as 3 5 and 6m vertical spacing cases
96
Oil
Prod
Rat
e SC
TR (m
3da
y)
0
20
40
60
80
100 Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-15 Oil Production Rate Vertical Inter-well Distance Optimization
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-16 Oil Recovery Factor Vertical Inter-well Distance Optimization
97
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-17 Steam Oil Ratio Vertical Inter-well Distance Optimization
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
0
10000
20000
30000
40000
50000
60000 Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-18 Steam Chamber Volume Vertical Inter-well Distance Optimization
98
5183 Vertical Injector
Vertical wellbores are cheaper and simpler to drill than the horizontal wellbores An
advantage of vertical wells with respect to horizontal well is that it is possible to change
the injection point as the SAGD project becomes mature Their disadvantage is that to
cover a horizontal wellbore several vertical wells are required Typically for every 150shy
200 m of horizontal well length a vertical well is needed Therefore for this study with
500 m long horizontal wells a well configuration with threetwo vertical injectors and a
horizontal producer was evaluated
The possibility of replacing the horizontal injector with sets of vertical injectors was
studied and the results are presented in this section Comparisons with the base case are
presented in Figures 5-19 5-20 5-21 and 5-22 The circulation of the vertical injectors
was achieved by introducing line heater on the injectors The heating period was the same
as base case preheating period Once the heating stage was terminated the injectors were
set on injection The model encountered some numerical instability during the first few
month of production but it stabled down for the rest of production period The results
demonstrate that using only two vertical injectors is not sufficient to deplete the reservoir
in 6 years of production window Its recovery factor is only 50 after 6 years of
production while its cSOR is close to 30 m3m3 However 3 vertical injectors case has
comparable RF results with the base case model which is about 65 after 6 years of
production but it requires larger amount of steam The steam chamber volume of the 3
vertical injectors is larger than the base case which demonstrates that the steam is
delivered more efficient than the base case Vertical injectors cause some instability in
numerical modeling once the steam zone of each vertical well merges to the adjacent
steam zone This issue was resolved using more refined grid blocks along the producer
99
Oil
Rat
e SC
(m3
day)
0
30
60
90
120
150 Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2009 2010 2011 2012 2013 2014 2015 2016 2017
Time (Date)
Figure 5-19 Oil Production Rate Vertical Injectors
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2009 2010 2011 2012 2013 2014 2015 2016 2017
Time (Date)
Figure 5-20 Oil Recovery Factor Vertical Injectors
100
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60
70
80
90
100 Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2009 2010 2011 2012 2013 2014 2015 2016 2017
Time (Date)
Figure 5-21 Steam Oil Ratio Vertical Injectors
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
0
10000
20000
30000
40000
50000
60000
70000 Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2009 2010 2011 2012 2013 2014 2015 2016 2017
Time (Date)
Figure 5-22 Steam Chamber Volume Vertical Injectors
101
5184 Reversed Horizontal Injector
It has been suggested that most of the injected steam in a basic SAGD pattern is
injected near the heel of the injector where the pressure difference between the injector
and producer is high Thus basic SAGD would yield an uneven and slanted chamber
along the well pair The Reversed Injector is introduced to solve the no uniformity of
steam chamber growth via a uniform pressure difference along the well pair This well
configuration is able to provide live steam along almost the whole length of the injector
and producer The vertical distance between the injector and producer is 5 m The
injectorrsquos heel is placed above the producerrsquos toe and its toe right above the producerrsquos
heel This well configuration creates an even pressure drop between the injector and
producer The steam chamber growth would be more uniform in all directions This
configuration uses the concept of countercurrent heat transfer and fluid flow
Figures 5-23 5-24 5-25 and 5-26 compare the technical performance of Reverse
Horizontal Injector and Base Case-SS
In both Base Case-SS and Reversed Horizontal Injector models a source-sink
wellbore type was used as Injector A line heater was introduced above the injector The
oil recovery factor increased by 4 with reversed injector while cSOR remained the
same as in the Base Case-SS while chamber volume increased by 89 As discussed in
the base case section currently the numerical simulators does not effectively model the
steam distribution (including pressure drop and injectivity) along the injectors and
therefore the results of Reversed Horizontal injector is close to the base case
Figure 5-26 displays a 3-D view of depleted reservoir using the Reversed Horizontal
Injector The chamber grows laterally longitudinally and vertically in a uniform manner
The results suggest that there is potential benefit for reversing the injector This
pattern provides the possibility of higher and uniform pressure operation This strongly
suggests that this pattern should be examined through a pilot project in Athabasca type of
reservoir
102
Oil
Prod
Rat
e SC
TR (m
3da
y)
0
20
40
60
80
100 Base Case-SS Reversed Horizontal Injector
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-23 Oil Production Rate Reverse Horizontal Injector
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS Reverse Horizontal Injector
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-24 Oil Recovery Factor Reverse Horizontal Injector
103
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS Reverse Horizontal Injector
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-25 Steam Oil Ratio Reverse Horizontal Injector
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
0
10000
20000
30000
40000
50000
60000 Base Case-SS Reverse Horizontal Injector
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-26 Steam Chamber Volume Reverse Horizontal Injector
104
One Year Five Years
Figure 5-27 3-D View of Chamber Growth Reverse Horizontal Injector
5185 Inclined Injector Optimization
Mojarab et al introduced a dipping injector above the producer It was shown that the
well configuration will provide a small improvement in the SAGD performance [95] For
simulating the inclined well the size of grid blocks in vertical direction was reduced to
appropriately capture the interferences at different angles The optimum distance at the
heel and toe was explored Table 5-5 presents the eight different cases that were
investigated
Table 5-5 Inclined Injector Case
Distance to Producer Heel m Distance to Producer Toe m Case 1 75 25 Case 2 8 3 Case 3 85 35 Case 4 9 4 Case 5 95 45 Case 6 10 5 Case 7 85 25 Case 8 95 25
The angle of injector inclination was varied to determine the optimum angle The
production results are compared against the basic pattern RF and cSOR results for all
inclined injector cases are presented in Figure 5-28 and 5-29 The injector was modeled
based on the SS wellbore modeling so the base case is the Base Case-SS model Figure
5-28 and 5-29 demonstrate that the Inclined Injector Case7 provides promising
performance It has increased the recovery factor by 31 while the cSOR was about the
same as in the Base Case-SS This configuration requires less than 3 months of steam
circulation
50
105
70
Oil
Rec
over
y Fa
ctor
SC
TR
Ste
am O
il R
atio
Cum
SC
TR (m
3m
3)
60
50
40
30
20
10
0
Time (Date) 2009 2010 2011 2012 2013 2014
Base Case-SS Inclined Inj Case 01 Inclined Inj Case 02 Inclined Inj Case 03 Inclined Inj Case 04 Inclined Inj Case 05 Inclined Inj Case 06 Inclined Inj Case 07 Inclined Inj Case 08
Figure 5-28 Oil Recovery Factor Inclined Injector
45
40
35
30
25
20
15
10
05
00
Time (Date) 2008-1-1 2009-5-15 2010-9-27 2012-2-9 2013-6-23 2014-11-5
Base Case-SS Inclined Inj Case 01 Inclined Inj Case 02 Inclined Inj Case 03 Inclined Inj Case 04 Inclined Inj Case 05 Inclined Inj Case 06 Inclined Inj Case 07 Inclined Inj Case 08
Figure 5-29 Steam Oil Ratio Inclined Injector
106
Oil
Rat
e SC
(m3
day)
0
20
40
60
80
100 Base Case-SS Inclined Inj Case 07
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-30 Oil Production Rate Inclined Injector Case 07
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS Inclined Inj Case 07
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-31 Oil Recovery Factor Inclined Injector Case 07
107
Ste
am O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS Inclined Inj Case 07
2008-1-1 2009-5-15 2010-9-27 2012-2-9 2013-6-23 2014-11-5 Time (Date)
Figure 5-32 Steam Oil Ratio Inclined Injector Case 07
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
0
10000
20000
30000
40000
50000
60000
Base Case-SS Inclined Inj Case 07
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-33 Steam Chamber Volume Inclined Injector Case 07
108
The results show that optimum distance at the heel and the toe can varies from 7-9 m
and 2-3 m respectively Figures 5-30 through 5-33 compare the results for optimum
Inclined Injector and the base case
5186 Parallel Inclined Injectors
In this pattern two 250 m long inclined injectors were placed above the producer
This well configuration is aimed at solving the nonuniformity of steam chamber along the
producer for long horizontal wellbores Nowadays the commercial projects are running
SAGD with well lengths of 1000 m or higher Consequently the degree of inclination in
the Inclined Injector pattern becomes small through 1000 meters of wellbore Since in the
current study the base case is defaulted as 500m therefore for this pattern two sets of
inclined injector are suggested Each injector has about 250 m length and their heels are
connected to the surface The heel to toe direction of both injectors is the same as
producer Both injectors are sourcesink type of wellbore and two line heaters were
introduced on the injectors to warm up the bitumen around them The heating period was
less than 3 months
The results obtained with dual inclined injectors above the producer are compared
with the Base Case-SS pattern in Figures 5-34 5-35 5-36 and 5-37 The parallel inclined
injector pattern provides higher RF but at the expense of larger cSOR The RF is
increased by 46 but on the other hand the cSOR increases by 44 as well
As the economic evaluation was not part of this project the conclusions are based on
the production performance only However it is obvious that an economic analysis would
be necessary for the final decision The main advantage of this well configuration is that
it has the flexibility of the vertical injector and deliverability of horizontal wellbores
109
Oil
Prod
Rat
e SC
TR (m
3da
y)
0
20
40
60
80
100 Base Case-SS Parallel Inclined Injectors
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-34 Oil Production Rate Parallel Inclined Injector
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS Parallel Inclined Injectors
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-35 Oil Recovery Factor Parallel Inclined Injector
110
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS Parallel Inlcined Injectors
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-36 Steam Oil Ratio Parallel Inclined Injector
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
0
10000
20000
30000
40000
50000
60000 Base Case-SS Parallel Inclined Injectors
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-37 Steam Chamber Volume Parallel Inclined Injector
111
5187 Multi-Lateral Producer
Unnecessary steam production is often associated with mature SAGD Large amount
of bitumen would be left behind in the area between the adjoining chambers It is
believed that a multi-lateral well could maximize overall oil production in a mature
SAGD Multi lateral wells are expected to provide better horizontal coverage than
horizontal wells and could extend the life of projects In order to increase the productivity
of a well the productive interval of the wellbore can be increased via well completion in
the form of multi-lateral wells A case study on the evaluation of multilateral well
performance is presented Multiple 30 m legs are connected to the producer
Figures 5-38 5-39 5-40 and 5-41 display the results for the Mutli-Lateral pattern
against the Base Case-SS The results are not dramatic The Multi-Lateral provides a
small benefit in recovery factor but not in cSOR Considering the cost involved in drilling
multilaterals this configuration does not appear promising This pattern may be a good
candidate for thin reservoirs which vertical access is limited and it would be more
beneficial to enlarge the horizontal distance between wellpairs
100
80
60
40
20
0
Oil
Prod
Rat
e SC
TR (m
3da
y)
Base Case-SS Multi-Lateral Producer
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-38 Oil Production Rate Multi-Lateral Producer
112
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS Multi-Lateral Producer
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-39 Oil Recovery Factor Multi-Lateral Producer
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS Multi-Lateral Producer
2009 2010 2011 2012 2013 2014
Time (Date)
Figure 5-40 Steam Oil Ratio Multi-Lateral Producer
113
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
70000
60000
50000
40000
30000
20000
10000
0
Base Case-SS Multi-Lateral Producer
2009 2010 2011 2012 2013 2014 Time (Date)
Figure 5-41 Steam Chamber Volume Multi-Lateral Producer
52 Cold Lake
The minimum depth to the first oil sand in Cold Lake area is ~300m while most
commercial thermal projects have occurred at the depth of about 450 m In Clearwater
formation the sands are often greater than 40m thick with a netgross ratio of greater than
05 Porosity ranges from 30 to 35 with oil saturations that average 70 PV At the
initial reservoir temperature of 13 degC the oil viscosity is about 100000 cp
521 Reservoir Model
Same as the numerical step in Athabasca reservoir section the (CMG) STARS
200913 software was used to numerically model the most optimum well configuration A
3-D symmetrical Cartesian model was created for this study The model is set to be
homogenous with averaged reservoir and fluid property to honor the properties in Cold
Lake area The model corresponds to a reservoir with the size of 30mtimes500mtimes20 m It
was covered with the Cartesian grid block size of 1times50times1 m in itimes jtimesk directions
respectively Figure 5-42 displays a 3-D view of the reservoir model
114
20
500
30
Figure 5-42 3-D schematic of Cold Lake reservoir model
The absolute permeability in horizontal direction is 5 D and the KvKh is set equal to
be 08 The porosity of sand is 34 The model is assumed to contain three phases with
bitumen water and methane as solution gas in bitumen
The initial oil saturation was assumed to be 85 with no gas cap above the oil
bearing zone The thermal properties of rock are provided in table 5-6 The heat losses to
over-burden and under-burden are taken into account as well CMG-STARS calculate the
heat losses to the cap rock and base rock analytically
The capillary pressure is set to zero as in the case of Athabasca reservoir
522 Fluid Properties
The fluid definition for Cold Lake reservoir (including K-Value definition and
values) followed the same steps as the one described in section 512 except the fact that
Cold Lake viscosity is different
To estimate a full range of viscosity vs temperature the Mehrotra and Svercek
viscosity correlation was used [93]
ln ln (μ) = A + B ln (T)
Figure 5-43 shows the viscosity-temperature variation for bitumen at cold lake area
115
1000000
100000
10000
1000
100
10
1
Visc
osity
cp
0 50 100 150 200 250 Temperature C
Figure 5-43 Viscosity vs Temperature for Cold Lake bitumen
523 Rock-Fluid Properties
The relative permeability data set is exactly the same as in the Athabasca model
Table 5-3 summarizes the rock-fluid properties The thermal properties of reservoir and
cap rock are the same as the ones were presented in Table 5-1 The water-oil and gas-oil
relative permeability curves are displayed in Figure 5-4 Figure 5-5 presents the relative
permeability sets for the grid blocks containing the well pairs
Table 5-6 Reservoir and fluid properties for Cold Lake reservoir model
Net Pay 20 m Depth 475 m Permeability Kh 5000 md KvKh 08 Porosity 34 Initial Pressure PR 2670 kPa Initial Temperature TR 15 degC Oil Saturation So 85 mole fraction Gas in Oil 6 Bitumen Density TR 949 Kgm3
300
116
524 Initial ConditionGeomechanics
The reservoir model top layer is located at a depth of 475 m and at initial temperature
of 15 ordmC The water saturation is at its critical value of 15 and the initial mole fraction
of gas in bitumen is 6 The total pore volume and oil phase volume are 128 and 109
E+5m3 respectively Geo-mechanical effects were ignored in the entire study except in
the C-SAGD well configuration
525 Wellbore Model
All the wells were modeled as DW except the non horizontal ones The non
horizontal injectors are modeled as line sourcesink combined with a line heater The line
heaters were shut in after the circulation period ended The DW consists of a tubing and
annulus which were defined as injector and producer respectively This would provide
the possibility of steam circulation during the preheating period
526 Wellbore Constraint
The injection well is constrained to operate at a maximum bottom hole pressure It
operates at 500 kPa above the reservoir pressure The steam quality is equal to 09 at the
sand-face The corresponding steam saturation temperature at the bottom-hole pressure is
237 degC The production well is assumed to produce under two major constraints
minimum bottom-hole pressure of 2670 kPa and steam trap of 10 degC The specified
steam trap constraints for producer will not allow any live steam to be produced via the
producer
527 Operating Period
Each numerical case was run for total of 4 years The preheating is variable between
1-4 months depending on the well configuration For the base case the circulation period
is 50 days which is approximately similar to the current industrial operations The main
production periods is approximately 3 years while the wind down takes only 1 year The
SAGD process stops when the oil rate declines below 10 m3d
117
528 Well Configurations
A series of comprehensive simulations were completed to explore the most promising
well configuration for the Clearwater formation in Cold Lake area First a base case
which has the classic well pattern (11 ratio with 5 m vertical inter-well spacing) was
modeled Then the performance of the other well patterns was compared against the base
case results The horizontal well length for both injector and producer was set at 500 m
Figure 5-44 displays the schematics of different well configurations These well
configurations need to be matched with specific reservoir characteristics for the optimum
performance None of them would be applicable to all reservoirs
5m
Injector
Producer
Injectors
Producer XY
Injector
Producer
Offset Horizontal InjectorBasic Well Configuration Vertical Injector
InjectorsInjectorsInjector
5m Producer Producer Producer
Reversed Horizontal Injector Parallel Inclined Injectors Parallel Reversed Upward Injectors
Injector Producer X
Multi Lateral Producer C-SAGD
Figure 5-44 Schematic representation of various well configurations for Cold Lake
5281 Base Case
This configuration introduces a wellpair consisting of injector and producer with the
vertical interwell distance of 5 m The producer is placed 15 m above the base of the net
pay Two distinct base cases were defined for future comparison a) both injector and
producer wellbores are modeled based on DW approach b) the injector is modeled with
SS wellbore approach and the producer is simulated with DW
The circulation period is 50 days and the reservoir is depleted in 4 years A close
examination of the chamber growth in both DW and SS models will show that that
STARS treats wellbores too idealistically The temperature profile along the wellpairs is
118
completely uniform during circulation as well as during the main SAGD stage However
in most of the field cases operators have difficulties in conveying the live steam to the
toe of injector for creating uniform steam chamber As a result the steam chamber will
have its maximum height at the heel of wellpairs and would become slanted along length
of the wellpairs This situation may create a potential for steam to breakthrough into the
producer resulting in difficulties in steam trap control and ultimately reduces the final
recovery factor
Therefore the new well configurations that have significantly higher chances of
activating the full well length will be considered successful configurations even when
their simulated performance is only slightly better than the base case
Figure 5-45 5-46 5-47 and 5-48 display the progression of the production for both
base cases during depletion of the reservoir
Both cases provided consistent results except for the cSOR The recovery factor for
both DW and SS models are pretty close to each other As per Figure 5-47 there is a
small difference in cSOR of DW and SS models with the respective values of 247 and
217 m3m3 In the Base Case-SS model a line heater was introduced above the injector
The heater with the modified constraint would provide sufficient heat into the intervening
zone between the injector and producer This supplied amount of energy is not included
in cSOR calculations which results in lower cSOR Therefore the difference in cSOR can
be ignored as well and both cases can be assumed to behave similarly
119
Oil
Prod
Rat
e SC
TR (m
3da
y)
0
20
40
60
80
100
120
140 Base Case-DW Base Case-SS
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-45 Oil Production Rate Base Case
Oil
Reco
very
Fac
tor
SCTR
0
10
20
30
40
50
60
70 Base Case-DW Base Case-SS
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-46 Oil Recovery Factor Base Case
120
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-DW Base Case-SS
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-47 Steam Oil Ratio Base Case
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
0
10000
20000
30000
40000
50000
60000 Base Case-DW Base Case-SS
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-48 Steam Chamber Volume Base Case
121
5282 Vertical Inter-well Distance Optimization
As discussed previously the optimum vertical inter-well distance between the
injector and producer depends on reservoir permeability bitumen viscosity and
preheating period To obtain the best RF and cSOR the vertical distance needs to be
optimized To study the effect of vertical inter-well distance on SAGD performance five
distances were considered 3 4 6 7 and 8m The idea was to investigate if changing the
vertical distance will improve the recovery factor and cSOR The oil rate RF cSOR and
the chamber volume are presented on Figures 5-49 5-50 5-51 and 5-52 It is observed
that the performance decreases with increasing the vertical distance When the distance is
smaller than the base case the preheating period is shortened but the effect on subsequent
performance is not dramatic The optimum vertical distance between the injector and
producer is assumed to be 5m in most of reservoir simulations and field projects Figures
5-50 and 5-51 show that the vertical distance can be varied from 3 to 6m and 4m appears
to be the optimal distance
Oil
Prod
Rat
e SC
TR (m
3da
y)
160
140
120
100
80
60
40
20
0
Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-49 Oil Production Rate Vertical Inter-well Distance Optimization
122
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-50 Oil Recovery Factor Vertical Inter-well Distance Optimization
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-51 Steam Oil Ratio Vertical Inter-well Distance Optimization
123
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
60000
50000
40000
30000
20000
10000
0
Base Case-DW Vertical Space=3m Vertical Space=4m Vertical Space=6m Vertical Space=7m Vertical Space=8m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-52 Steam Chamber Volume Vertical Inter-well Distance Optimization
5283 Offset Horizontal Injector
The interwell distance between the injector and producer depends on reservoir
permeability bitumen viscosity and preheating period Cold Lake contains bitumen with
the average viscosity of about 100000 cp which can be ranked as a lower viscosity
reservoir among the bitumen saturated sands Cold Lake bitumen offers a tempting option
of offsetting injector from producer The idea behind offsetting the injector is to increase
the drainage area available for the SAGD draw-down despite the fact that both recovery
factor and cSOR would be comparable to the Base Case pattern Therefore it is appealing
to consider a configuration when the injector is positioned at an offset of certain distance
from the producer In order to operate a SAGD project with offset injector the vertical
interwell distance needs to be small The vertical distance is assumed to be either 2m or
3m while the offset distances are set to be 5m and 10m
Four cases were simulated to investigate the possibility of offsetting the injector for a
SAGD process a) Vertical distance of 2m with the horizontal offset of 5m b) Vertical
124
distance of 2m with the horizontal offset of 10m c) Vertical distance of 3m with the
horizontal offset of 5m and d) Vertical distance of 3m with the horizontal offset of 10m
Figures 5-53 5-54 5-55 and 5-56 show that there is some benefit in providing extra
horizontal spacing According to the oil production profile and recovery factor 10m
offset does not offer any advantage to a SAGD process in Cold Lake it decreases the RF
and dramatically increases the cSOR The 10m horizontal offset requires long preheating
period which results in high cSOR Once the communication between injector and
producer established due to high viscosity of the bitumen and large horizontal spacing
between injector and producer the steam chamber does not get stable and the oil rate
fluctuates during the course of production The steam chamber does not grow uniformly
along the injector and major amount of bitumen is left unheated When the horizontal
offset is around 5m there is some improvement in RF but at the expense of higher cSOR
Oil
Prod
Rat
e SC
TR (m
3da
y)
160
140
120
100
80
60
40
20
0 2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Base Case-DW Offset Horizontal Injector VD=2m-Off=5m Offset Horizontal Injector VD=2m-Off=10m Offset Horizontal Injector VD=3m-Off=5m Offset Horizontal Injector VD=3m-Off=10m
Time (Date)
Figure 5-53 Oil Production Rate Offset Horizontal Injector
125
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-DW Offset Horizontal Injector VD=2m-Off=5m Offset Horizontal Injector VD=2m-Off=10m Offset Horizontal Injector VD=3m-Off=5m Offset Horizontal Injector VD=3m-Off=10m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-54 Oil Recovery Factor Offset Horizontal Injector
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60
70
80
90
100
Base Case-DW Offset Horizontal Injector VD=2m-Off=5m Offset Horizontal Injector VD=2m-Off=10m Offset Horizontal Injector VD=3m-Off=5m Offset Horizontal Injector VD=3m-Off=10m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-55 Steam Oil Ratio Offset Horizontal Injector
126
60000
50000
40000
30000
20000
10000
0
Time (Date)
Figure 5-56 Steam Chamber Volume Offset Horizontal Injector
5284 Vertical Injector
As discussed previously the vertical wellbores are included in each part of the current
study because of their advantages over the horizontal ones such as drilling price ease of
operation flexibility of operation Typically for every 150-200 m of horizontal well
length a vertical well is needed Therefore for this study with 500 m long horizontal
wells a well configuration with threetwo vertical injectors and a horizontal producer was
evaluated
The possibility of replacing the horizontal injector with sets of vertical injectors was
studied and the results are presented in this section Comparisons with the base case are
presented in Figures 5-57 5-58 5-59 and 5-60
As was seen in Athabasca section the results demonstrate that two vertical injectors
are not sufficient to deplete a 500m long reservoir since its recovery factor reaches 55
after four years of production with a steam oil ratio of 30 m3m3 On the other hand the
three vertical injectors case provides comparable RF with respect to base case RF but at
larger amount of injected steam The RF and cSOR of three vertical injectors is 63 and
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
Base Case-DW Offset Horizontal Injector VD=2m-Off=5m Offset Horizontal Injector VD=2m-Off=10m Offset Horizontal Injector VD=3m-Off=5m Offset Horizontal Injector VD=3m-Off=10m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
127
32 m3m3 respectively The steam chamber volume of the 3 vertical injectors is larger
than the base case which demonstrates that the steam is delivered more efficient than the
base case
The line heater was used to establish the thermal communication between the vertical
injectors and producer The heating period was the same as base case preheating period
Once the intervening bitumen between injector and producer is warmed up the injectors
were set on injection Vertical injectors caused some instability in numerical modeling
once the steam zone of each vertical well merges to the adjacent steam zone This issue
was resolved using more refined grid blocks along the producer
Oil
Prod
Rat
e SC
TR (m
3da
y)
180
160
140
120
100
80
60
40
20
0
Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-57 Oil Production Rate Vertical Injectors
128
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-58 Oil Recovery Factor Vertical Injectors
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-59 Steam Oil Ratio Vertical Injectors
129
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
60000
50000
40000
30000
20000
10000
0
Base Case-SS 2 Vertical Injectors 3 Vertical Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-60 Steam Chamber Volume Vertical Injectors
5285 Reversed Horizontal Injector
This pattern was well described previously and its aim was defined to establish a
uniform steam chamber along the well-pairs by imposing a uniform pressure difference
along the injectorproducer vertical interwell distance This well configuration is able to
provide live steam almost along the whole length of the injector and producer The
vertical distance between the injector and producer is 5 m The injectorrsquos heel is placed
above the producerrsquos toe and its toe right above the producerrsquos heel The steam chamber
growth is uniform in three main directions vertically laterally and longitudinally
The oil rate RF cSOR and the chamber volume are plotted on Figures 5-61 5-62 5shy
63 and 5-64 The technical performance of Reverse Horizontal Injector and Base Case-
DW are compared In both Base Case-DW and Reversed Horizontal Injector models a
discretized wellbore formulation was used as Injector Oil recovery factor increased by
2 but the cSOR was the same as Basic Case-DW
The results suggest that there is a potential benefit for reversing the injector in Cold
Lake type of reservoir This pattern provides the possibility of higher and uniform
130
pressure operation This strongly suggests that this pattern be examined through a pilot
project in Cold Lake type of reservoir
Oil
Prod
Rat
e SC
TR (m
3da
y)
140
120
100
80
60
40
20
0
Base Case-DW Reversed Horizontal Injector
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-61 Oil Production Rate Reverse Horizontal Injector
131
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-DW Reverse Horizontal Injector
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-62 Oil Recovery Factor Reverse Horizontal Injector
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-DW Reverse Horizontal Injector
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-63 Steam Oil Ratio Reverse Horizontal Injector
132
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
60000
50000
40000
30000
20000
10000
0
Base Case-DW Reverse Horizontal Injector
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-64 Steam Chamber Volume Reverse Horizontal Injector
5286 Parallel Inclined Injectors
Vertical horizontal and inclined injectors provide some advantages for the SAGD
process namely flexibility of injection point extensive access to the reservoir and short
circulation period The parallel Inclined Injector was designed to combine all these
benefits together In this pattern two 250 m inclined injectors were located above the
producer
The pattern is shown in Figure 5-44 The injectors were defined using the SS
wellbore formulation therefore the results are compared against the Base Case-SS
pattern Figures 5-65 5-66 5-67 and 5-68 present the ultimate production results for the
Parallel Inclined Injectors The recovery factor increased by 36 but the cSOR also
increased by 138
133
Oil
Prod
Rat
e SC
TR (m
3da
y)
0
20
40
60
80
100
120
140 Base Case-SS Parallel Inclined Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-65 Oil Production Rate Parallel Inclined Injector
Oil
Reco
very
Fac
tor
SCTR
0
10
20
30
40
50
60
70 Base Case-SS Parallel Inclined Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-66 Oil Recovery Factor Parallel Inclined Injector
134
50
45
40
35
30
25
20
15
10
05
00
Base Case-SS Parallel Inlcined Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-67 Steam Oil Ratio Parallel Inclined Injector
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
0
10000
20000
30000
40000
50000
60000 Base Case-SS Parallel Inclined Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
Figure 5-68 Steam Chamber Volume Parallel Inclined Injector
135
5287 Parallel Reversed Upward Injectors
Parallel inclined injector and reversed horizontal showed encouraging performance in
comparison with the Base case Combining the advantages gained via these two well
configurations the Parallel Reversed Upward Injectors was proposed Two upward
inclined injectors were introduced above the producer The main thought behind this
special design is to provide a uniform pressure profile along the injector and producer
and resolve the unconformity of steam chamber associated with the Base Case pattern
Each injector has about 250 m length and their heels are connected to the surface The
first injector has its heel above the toe of producer
Figure 5-69 5-70 5-71 and 5-72 compare the technical performance of Parallel
Reversed Inclined Injectors and Base Case-SS The recovery factor and cSOR increased
by 55
Oil
Prod
Rat
e SC
TR (m
3da
y)
140
120
100
80
60
40
20
0
Base Case-SS Parallel Reverse Upward Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-69 Oil Production Rate Parallel Reverse Upward Injector
136
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS Parallel Reverse Upward Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-70 Oil Recovery Factor Parallel Reverse Upward Injector
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS Parallel Reverse Upward Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-71 Steam Oil Ratio Parallel Reverse Upward Injector
137
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
60000
50000
40000
30000
20000
10000
0
Base Case-SS Parallel Reverse Upward Injectors
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-72 Steam Chamber Volume Parallel Reverse Upward Injector
5288 Multi-Lateral Producer
Economic studies show that SAGD mechanism is not feasible in thin reservoirs due
to enormous heat loss and consequently high cSOR [90] Therefore the low RF
production mechanisms such as cold production will continue to be used for extraction of
heavy oil On the other hand in Cold Lake type of reservoir unnecessary steam
production is often associated with mature SAGD and large amount of bitumen would be
left behind in the area between the chambers In order to access more of the heated
mobilized bitumen and increase the productivity of a well the productive interval of the
wellbore can be increased via well completion in the form of multi-lateral wells Multishy
lateral wells are expected to provide better horizontal coverage than horizontal wells and
they can extend the life of projects A simulation study on the evaluation of multilateral
well performance is presented Multiple 30 m legs are connected to the producer
Figure 5-73 5-74 5-75 and 5-76 show the results for Mutli-Lateral pattern against
the Base Case-SS The Multi-Lateral depletes the reservoir significantly faster than the
138
basic pattern The plotted results demonstrate that the Multi-Lateral is not able to provide
any other significant benefits over the performance of base case SAGD
Oil
Prod
Rat
e SC
TR (m
3da
y)
140
120
100
80
60
40
20
0
Base Case-SS Multi-Lateral Producer
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-73 Oil Production Rate Multi-Lateral Producer
139
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70 Base Case-SS Multi-Lateral Producer
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-74 Oil Recovery Factor Multi-Lateral Producer
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
05
10
15
20
25
30
35
40
45
50 Base Case-SS Multi-Lateral Producer
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-75 Steam Oil Ratio Multi-Lateral Producer
140
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
70000
60000
50000
40000
30000
20000
10000
0
Base Case-SS Multi-Lateral Producer
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-76 Steam Chamber Volume Multi-Lateral Producer
5289 C-SAGD
At Cold Lake Cyclic Steam Stimulation has been successfully used as the main
recovery mechanism because there are often heterogeneities in form of shale barriers that
are believed to limit the vertical growth of steam chamber and consequently decrease the
efficiency of thermal methods In CSS process the steam is injected at high pressure
(usually higher than the fracture pressure) into the reservoir its high pressure creates
some fractures in the reservoir and its high temperature causes a significant drop in
bitumen viscosity As a result a high mobility zone will be created around the wellbore
which the fluids (melted bitumen and condensate) can flow back into the wellbore The
fracturing stage is known as deformation which includes dilation and re-compaction
Beatle et al defined a deformation model which is presented in Figure 5-77 [96]
During the steam injection into the reservoir the reservoir pressure increases and the
rock behaves elastically The rock pore volume at the new pressure will be obtained
based on the rock compressibility initial reservoir pressure and initial porosity If the
reservoir pressure increases above the so called pdila then the reservoir pore volume
141
follows the dilation curve which is irreversible It may reach the maximum porosity If
the pressure decreases from any point on the dilation curve then the reservoir pore
volume follows the elastic compaction curve If the pressure drops below the re-
compaction pressure ppact re-compaction occurs and the slop of the curve is calculated
by the residual dilation fraction fr
Figure 5-77 Reservoir deformation model [96]
Every single cycle of a CSS process follows the entire deformation envelope The
deformation properties of the cold lake reservoir are provided in Table 5-7 [97]
Table 5-7 Values of dilation-compaction properties for Cold Lake reservoir model
pdila 7300 kPa ppact 5000 kPa φmax 125 φi Residual Dilation Fraction fr 045 Dilation Compressibility 10 E-4 1kPa
The C-SAGD pattern is aimed at combining the benefits of CSS and SAGD together
This configuration starts with one cycle of CSS at both injector and producer locations to
create sufficient mobility in vicinity of both wellbores The one cycle comprises the
steam injection soaking and production stage The CSS cycle starts with 20 days of
steam injection at a maximum pressure of 10000 kPa on both injector and producer 7
142
days of soaking and approximately two months of production Thereafter it switches
into normal SAGD process by injection of steam from injector and producing via
producer The constraints of injector and producer are the same as values are presented in
section 526 The objective of the C-SAGD well pattern is to decrease the preheating
period without affecting the ultimate recovery factor and cumulative steam oil ratio The
injector and producer are placed at the same depth with two set of offsets 10m and 15m
Their results are compared against the Base Case It has to be noted that both injector and
producer in the C-SAGD patter are modeled using the SS wellbore As a result some
marginal value (due to higher pressure and injection rate approximately larger than 02shy
03 m3m3) has to be added to their ultimate cSOR value Figure 5-78 5-79 5-60 and 5shy
61 presents the oil rate RF cSOR and the chamber volume of the two C-SAGD cases in
comparison with the base case results
Oil
Prod
Rat
e SC
TR (m
3da
y)
300
270
240
210
180
150
120
90
60
30
0
Base Case-DW C-SAGD-Offset=10m C-SAGD-Offset=15m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-78 Oil Production Rate C-SAGD
143
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70
80 Base Case-DW C-SAGD-Offset=10m C-SAGD-Offset=15m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-79 Oil Recovery Factor C-SAGD
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60
70
80
90
100 Base Case-DW C-SAGD-Offset=10m C-SAGD-Offset=15m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1
Time (Date)
Figure 5-80 Steam Oil Ratio C-SAGD
144
Stea
m C
ham
ber
Volu
me
SCTR
(m3)
90000
80000
70000
60000
50000
40000
30000
20000
10000
0
Base Case-DW C-SAGD-Offset=10m C-SAGD-Offset=15m
2008-7 2009-1 2009-7 2010-1 2010-7 2011-1 2011-7 2012-1 Time (Date)
Figure 5-81 Steam Chamber Volume C-SAGD
The C-SAGD pattern with the offset of 10m is able to deplete the reservoir in 3 years
at ~70 RF and cSOR of 22 m3m3 (needs to add ~02-03 m3m3 due to SS injector and
producer) The pattern enhances the RF of SAGD process significantly The only
limitation with this pattern for the current research scope is the requirement for super
high injection pressure for a short period of time
53 Lloydminster
Steam-flooding has been practiced extensively in North America Generally speaking
steam is introduced into the reservoir via a horizontalvertical injector while the heated
oil is being pushed towards the producer Several types of repeated patterns are known to
provide the most efficient recovery factor The major issues with the steam flooding
process are (1) steam tends to override the heavy oil and breaks through to the
production well and (2) the steam has to displace the cold heavy oil into the production
well These concerns make steam flooding inefficient in reservoirs containing heavy oil
with reservoir condition viscosities higher than 1000 cp However in SAGD type of
Net
145
process the heated oil remains hot as it flows into the production well Figure 5-82 shows
both steam flooding and SAGD processes
At Lloydminster area the reservoirs are mostly complex and thin with a wide range
oil viscosity These characteristics of the Lloydminster reservoirs make most production
techniques such as primary depletion waterflood CSS and steamflood relatively
inefficient The highly viscous oil coupled with the fine-grained unconsolidated
sandstone reservoir often result in huge rates of sand production with oil during primary
depletion Although these techniques may work to some extent the recovery factor
remains low (5 to 15) and large volumes of oil are left unrecovered when these
methods have been exhausted Because of the large quantities of sand production many
of these reservoirs end up with a network of wormholes which make most of the
displacement type enhanced oil recovery techniques inapplicable Steam Oil amp Water
Overburden
Underburden
Steam Chamber
Underburden
Overburden
Vertical Cross Section of SAGD Vertical Cross Section of Steamflood
Figure 5-82 Schematic of SAGD and Steamflood
For heavy oil reservoirs containing oil with the viscosity smaller than 5000 cp both
SAGD and steamflooding can be considered applicable for extraction of the heavy oil In
fact this type of reservoir provides more flexibility in designing the thermal recovery
techniques as a result of their higher mobility and steam injectivity Steam can be pushed
and forced into the reservoir displacing the heavy oil and creating more space for the
chamber to grow On the other hand due to small thickness of the net pay the heat loss
could make the process uneconomical for both methods However steamflood faces its
own additional problems as well no matter where it is applied For the SAGD case
146
although drainage by the SAGD mechanism from the steam chamber to the production
well is conceivable due to the small pay thickness the gravity forces may not be large
enough to provide economical drainage rates
Unfortunately SAGD has not received adequate attention in Lloydminster area
mostly due to the notion that lower drainage rate and higher heat loss in thin reservoirs
would make the process uneconomical While this may be true the limiting reservoir
thickness and inter-well horizontal distance for SAGD under varying conditions has not
been established These reservoirs contain oil with sufficient mobility Therefore the
communication between the SAGD well pairs is no longer a hurdle This opens up the
possibility of increasing the distance between the two wells and introducing elements of
steamflooding into the process in order to compensate for the small thickness of the
reservoir In fact a new application of SAGD mechanism for the reservoir with the
conventional heavy oil could be the combination of an early lateral steam drive with
SAGD afterwards In this scheme steam would be injected from an offset horizontal
injector pushing the oil towards the producer Once the communication between injector
and producer is established the recovery mechanism will be changed to a SAGD process
by applying steam trap control to the production well
Among the whole Mannville group the formations that have potential to be
considered as oil bearing zone are Waseca Sparky GP and Lloydminster These
sandstone channels thicknesses may rarely go up to 20m and the oil saturation up to 80
Their porosity ranges from 30-35 percent and permeability from 5 to 10 Darcyrsquos
Mannville group contains both conventional and heavy oil with the API ranging from 15shy
38 degAPI and viscosity of 800-20000 cp at 15 degC
531 Reservoir Model
The optimization of the well configuration study was carried out via a series of
numerical simulations using CMGrsquos STARS 2010 A 3-D symmetrical-Cartesianshy
homogenous reservoir model was used to conduct the comparison analysis between
different well configurations The reservoir and fluid properties were simply averaged to
present the best representative of Lloydminster deposit The model corresponds to a
reservoir with the size of 90mtimes500mtimes10 m using the Cartesian grid block sizes of
147
1times50times1 in itimes jtimesk directions respectively Figure 5-83 displays a 3-D view of the
reservoir model
10
500
90
Figure 5-83 3-D schematic of reservoir model for Lloydminster reservoir
The reservoir and fluid properties are summarized in Table 5-8 The rock properties
are the same as Athabasca and Cold Lake
532 Fluid Properties
As in simulations of Athabasca and Cold Lake reservoirs three components were
included in the reservoir model as Oil water and methane The thermal properties of the
fluid and rock were obtained from the published literature The properties of the water in
both aqueous and gas phase were set as the default values of the CMG-STARS The
properties of the fluid (oil and methane) model are provided in Table 5-8
The K-Values of methane are the same as the numbers presented for Athabasca and Cold
Lake reservoirs
To estimate a full range of viscosity vs temperature the Mehrotra and Svercek
viscosity correlation was used [93]
ln ln (μ) = A + B ln (T) Figure 5-84 shows the viscosity-temperature variation for the heavy oil model
Rock fluid properties are the same as the relative permeability sets presented for
Athabasca and Cold Lake reservoirs
148
Table 5-8 Reservoir and Fluid Properties for Lloydminster reservoir model
Net Pay 10 m Depth 450 m Permeability Kh 5000 md KvKh 08 Porosity 34 Initial Pressure PR 4100 kPa Initial Temperature TR 20 degC Oil Saturation So 80 mFrac Gas in Oil 10 Oil Viscosity TR 5000 cp
533 Initial ConditionsGeomechanics
The reservoir model top layer is located at a depth of 450 m and at initial temperature
of 20 ordmC The water saturation is at its critical value of 20 and the initial mole fraction
of gas in heavy oil is 10 The total pore volume and oil phase volume are 192 and 154
E+5m3
Geo-mechanical effects were ignored in the entire study except the C-SAGD pattern
534 Wellbore Constraint
The well length was kept constant at a value of 500m The injection well was
constrained to operate at a maximum bottom hole pressure It operated at 500 kPa above
the reservoir pressure The steam quality was equal to 09 at the sand-face The
corresponding steam saturation temperature at the bottom-hole pressure is 2588 degC
The production well is assumed to produce under two major constraints minimum
bottom-hole pressure of 1000-2000 kPa and steam trap of 10 degC (The 1000 kPa is for
the offset of larger than 30 m) The specified steam trap constraints for producer will not
allow any live steam to be produced via the producer
149
10000
Visc
osity
cp
1000
100
10
1 0 50 100 150 200 250
TemperatureC
Figure 5-84 Temperature dependency of heavy oil modelrsquos Viscosity
535 Operating Period
Each numerical case was run for total of 7 years The preheating is variable for
Lloydminster area and it really depends on the well configuration and wellbore offset
536 Well Configurations
The basic well pattern is practical for the reservoirs with the thickness of higher than
20 m as the vertical inter-well distance is 5 m and the producer is placed at least 15 m
above the base of the pay zone However depending on the reservoir thickness and oil
properties it might be advantageous to drill several horizontalvertical wells at different
levels of the reservoir ie employ other configurations than the classic one to enhance the
drainage and heat loss efficiency These well configurations need to be matched with
specific reservoir characteristics for the optimum performance
When two parallel horizontal wells are employed in SAGD the relevant
configuration parameters are (a) height of the producer above the base of the reservoir
(b) the vertical distance between the producer and the injector and (c) the horizontal
300
150
separation between the two wells which is zero in the base case configuration Although
the assumed net pay for the Lloydminster reservoir is 10 m but just for sake of
comparison the base case is the same pattern was defined before ie an injector located
5m above the producer which is the case under the name of VD=5m_Offset=0m
Figure 5-85 displays the schematics of different well configurations These well
configurations need to be matched with specific reservoir characteristics for the optimum
performance None of them would be applicable to all reservoirs
Injectors Produce Injectors
Injector
5m Producer Producer
Basic Well Configuration Offset Producer Top View Vertical Injector
Injectors Produce Injectors Produce
Injector Producer X
C-SAGD ZIGZAG Producer Top View Multi Lateral Producer Top View
Figure 5-85 Schematic of various well configurations for Lloydminster reservoir
The SS wellbore type is used in all the defined well configurations for Lloydminster
In fact due to some of the special patterns such as C-SAGD some high differential
pressure and consequently high fluid rates are required which the DW modeling is not
able to model properly As a result some marginal value has to be added to their ultimate
cSOR value in order to compensate for replacing DW by SS wellbore
Two types of start-up are used in initializing the proposed patterns in Figure 5-85 a)
routine SAGD steam circulation b) one CSS cycle Due to the nature of fluid and
reservoir in Lloydminster area initial oil viscosity of 5000 cp at reservoir temperature
the initial mobility is high but not sufficient for a cold production start The primary
production leads to a small recovery factor and would create worm holes in the net pay
Therefore some heat is required to be injected into the reservoir to mobilize the heavy oil
Among the six proposed well patterns only C-SAGD initializes the production by
one cycle of CSS In C-SAGD pattern the steam at high pressure of 10000 kPa is
151
injected in both injector and producer thereafter both wells were shut-in for a week
(soaking period) The heated mobilized heavy oil around the injector and producer were
produced for approximately 4 months Eventually the steam was injected via injector and
pushed the heavy oil towards the producer which was set at a minimum bottom-hole
pressure of 1000 kPa The start-up stage in the rest of the patterns follows the same
routing steps of a regular SAGD process steam circulation which followed by
injectionproduction via injector and producer The steam circulation is achieved by
defining a line heater above the injector and producer The period of steam circulation
really depends on the well pair horizontal spacing and is variable among each pattern
5361 Offset Producer
The lower viscosity of the Lloydminster deposit comparing to Cold Lake and
Athabasca reservoirs opens up the possibility of increasing the distance between the two
wells and introducing elements of steam flooding into the process in order to compensate
for the small thickness of the reservoir Due to the low viscosity and sufficient mobility
the communication between the SAGD well pairs may be no longer a hurdle Therefore
the horizontal separation between the two well is more flexible in Lloydminster type of
reservoir and due to the small thickness of the net pay the vertical distance needs to be as
small as possible
The objective of the offset producer pattern is to increase the horizontal spacing
between wells as much as possible To establish the chamber on top of the well pairs
which are separated horizontally the fact that any increase in the well spacing may
require more circulation period needs to be considered Horizontal well spacing of 6 12
24 30 36 and 42 m were tested to obtain the optimum performance The circulation
period was varied between 20 and 80 days which occurred at 6m and 42m offset
producer Figure 5-86 5-87 5-88 and 5-89 shows the results for the offset injector
against the Base Case-DW
152
Oil
Rat
e SC
(m3
day)
0
20
40
60
80
100
120
140
160
180
200 VD=5m-Offset=0m VD=0m-Offset=6m VD=0m-Offset=12m VD=0m-Offset=18m VD=0m-Offset=24m VD=0m-Offset=30m VD=0m-Offset=36m VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-86 Oil Production Rate Offset Producer
Oil
Rec
over
y Fa
ctor
SC
TR
0
15
30
45
60
75 VD=5m-Offset=0m VD=0m-Offset=6m VD=0m-Offset=12m VD=0m-Offset=18m VD=0m-Offset=24m VD=0m-Offset=30m VD=0m-Offset=36m VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-87 Oil Recovery Factor Offset Producer
153
Cum
Ste
am O
il R
atio
(m3
m3)
00
10
20
30
40
50
60 VD=5m-Offset=0m VD=0m-Offset=6m VD=0m-Offset=12m VD=0m-Offset=18m VD=0m-Offset=24m VD=0m-Offset=30m VD=0m-Offset=36m VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-88 Steam Oil Ratio Offset Producer
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
00e+0
20e+4
40e+4
60e+4
80e+4
10e+5 VD=5m-Offset=0m VD=0m-Offset=6m VD=0m-Offset=12m VD=0m-Offset=18m VD=0m-Offset=24m VD=0m-Offset=30m VD=0m-Offset=36m VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-89 Steam Chamber Volume Offset Producer
154
The minimum RF is 66 which belongs to the base case 42m offset producer pattern
and the maximum obtained RF is 71 which obtained by the 30m offset On the other
hand the 42m and 36m offset producer provide the minimum steam oil ratio of 46 m3m3
Among all the offset patterns the 30m offset producer provides the most optimum
performance Therefore it can be concluded that if any offset horizontal well is decided
to be drilled in Lloydminster type of reservoir the horizontal inter-well distance can not
be larger than 30m
5362 Vertical Injector
According to early experience of SAGD in Lloydminster area vertical wells were
considered as successful with the steam oil ratio of 3-6 m3m3 [98] Generally 3-4 vertical
injection wells with an offset of 50m have been used for a 500m long horizontal
producer There is an unanswered question of how much of horizontal offset should be
considered between vertical injectors and horizontal producers so that the SAGD would
achieve optimum performance Vertical injector well configuration was tested using 3
vertical wells combined with a horizontal producer using the offsetting values of 0 6 12
18 24 30 36 and 42 horizontal wells The zero offset case locates the three vertical
injectors above the producer imposing 4 m of vertical inter-well distance In the rest of
offset cases the injectorrsquos completed down to the producerrsquos depth The comparison
between the base case results and the vertical well scenarios are presented in Figure 5-90
5-91 5-92 and 5-93
The pattern which has 3 vertical injectors 5m above the producer exhibits the best
performance regarding the RF and cSOR It RF equals to 70 while its cSOR is 52
m3m3 However the 42m offset vertical injectors pattern has a promising performance
with an extra benefit This pattern allows to enlarge the drainage area by 42m which will
affect the number of required well to develop a full section much less than the no offset
vertical injectors
155
Oil
Rat
e SC
(m3
day)
0
30
60
90
120
150
180
210 VD=5m-Offset=0m 3VW-VD=5m-Offset=0m 3VW-VD=0m-Offset=6m 3VW-VD=0m-Offset=12m 3VW-VD=0m-Offset=18m 3VW-VD=0m-Offset=24m 3VW-VD=0m-Offset=30m 3VW-VD=0m-Offset=36m 3VW-VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-90 Oil Production Rate Vertical Injector
Oil
Rec
over
y Fa
ctor
SC
TR
0
12
24
36
48
60
72
VD=5m-Offset=0m 3VW-VD=5m-Offset=0m 3VW-VD=0m-Offset=6m 3VW-VD=0m-Offset=12m 3VW-VD=0m-Offset=18m 3VW-VD=0m-Offset=24m 3VW-VD=0m-Offset=30m 3VW-VD=0m-Offset=36m 3VW-VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-91 Oil Recovery Factor Vertical Injector
156
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60 VD=5m-Offset=0m 3VW-VD=5m-Offset=0m 3VW-VD=0m-Offset=6m 3VW-VD=0m-Offset=12m 3VW-VD=0m-Offset=18m 3VW-VD=0m-Offset=24m 3VW-VD=0m-Offset=30m 3VW-VD=0m-Offset=36m 3VW-VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-92 Steam Oil Ratio Vertical Injector
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
00e+0
20e+4
40e+4
60e+4
80e+4
10e+5 VD=5m-Offset=0m 3VW-VD=5m-Offset=0m 3VW-VD=0m-Offset=6m 3VW-VD=0m-Offset=12m 3VW-VD=0m-Offset=18m 3VW-VD=0m-Offset=24m 3VW-VD=0m-Offset=30m 3VW-VD=0m-Offset=36m 3VW-VD=0m-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-93 Steam Chamber Volume Vertical Injector
157
5363 C-SAGD
The C-SAGD pattern was simulated in Cold Lake reservoir and its results were
promising Due to low oil viscosity and thickness at Lloydminster reservoir it is desired
to shorten the circulation period as much as possible The C-SAGD provides the
possibility to establish the communication between injector and producer in minimal time
period As explained earlier in Cold Lake section this pattern comprises of one CSS
cycle at both injector and producer locations and thereafter it switches to regular SAGD
process The CSS cycle starts with 15 days of steam injection at a maximum pressure of
10000 kPa on both injector and producer 7 days of soaking and approximately three
months of production Thereafter it switches into normal SAGD process by injection of
steam from injector and producing via producer During the normal SAGD the
constraints of injector and producer are the same as values are presented in section 544
The injector and producer are placed at the same depth with the offsetting spacing of 6
12 18 24 30 36 and 42 m Figures 5-94 5-95 5-96 5-97 present the C-SAGD results
According to RF results the offset of 6 and 12m is small for a C-SAGD process But
since the horizontal inter-well distance between the injector and producer gets larger the
RF will be somewhere around 80 which sounds quite efficient The patterns with an
offset value of larger than 12m are able to deplete the reservoir with a cSOR in the range
of 6-65 m3m3 According to the results the most optimum horizontal inter-well spacing
is 42m since it has the highest RF the lowest cSOR and provides the opportunity to
enlarge the drainage area
158
Oil
Rat
e SC
(m3
day)
0
30
60
90
120
150
180
210 VD=5m-Offset=0m C-SAGD-Offset=6m C-SAGD-Offset=12m C-SAGD-Offset=18m C-SAGD-Offset=24m C-SAGD-Offset=30m C-SAGD-Offset=36m C-SAGD-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-94 Oil Production Rate C-SAGD
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70
80
90 VD=5m-Offset=0m C-SAGD-Offset=6m C-SAGD-Offset=12m C-SAGD-Offset=18m C-SAGD-Offset=24m C-SAGD-Offset=30m C-SAGD-Offset=36m C-SAGD-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-95 Oil Recovery Factor C-SAGD
159
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60
70
VD=5m-Offset=0m C-SAGD-Offset=6m C-SAGD-Offset=12m C-SAGD-Offset=18m C-SAGD-Offset=24m C-SAGD-Offset=30m C-SAGD-Offset=36m C-SAGD-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-96 Steam Oil Ratio C-SAGD
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
00e+0
20e+4
40e+4
60e+4
80e+4
10e+5
12e+5 VD=5m-Offset=0m C-SAGD-Offset=6m C-SAGD-Offset=12m C-SAGD-Offset=18m C-SAGD-Offset=24m C-SAGD-Offset=30m C-SAGD-Offset=36m C-SAGD-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-97 Steam Chamber Volume C-SAGD
160
5364 ZIGZAG Producer
A new pattern called ldquoZIGZAGrdquo was designed and compared against the horizontal
offsets The objective for this well pattern was to shorten the circulation period without
affecting the ultimate performance The horizontal inter-well distance between the
injector and producer are assumed as 12 18 24 30 36 and 42 m The producer enters
into the formation at X meters offset of the injector but it approaches toward the injector
up to X2 meters away from injector and it bounce back to its primary location of X
meters from injector This move repeatedly occurs throughout the length of injector The
results of ZIGZAG pattern are provided in Figures 5-98 5-99 5-100 and 5-101
Increasing the offset between injector and producer enhance the performance which has
the same trend in other configurations The 42m offset depletes the reservoir much faster
while it exhibits the highest RF of 78 and lowest cSOR of 5 m3m3
Oil
Rat
e SC
(m3
day)
180
160
140
120
100
80
60
40
20
0
VD=5m-Offset=0m ZIGZAG-Offset=12m ZIGZAG-Offset=18m ZIGZAG-Offset=24m ZIGZAG-Offset=30m ZIGZAG-Offset=36m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016 Time (Date)
Figure 5-98 Oil Production Rate ZIGZAG
161
Oil
Rec
over
y Fa
ctor
SC
TR
0
10
20
30
40
50
60
70
80 VD=5m-Offset=0m ZIGZAG-Offset=12m ZIGZAG-Offset=18m ZIGZAG-Offset=24m ZIGZAG-Offset=30m ZIGZAG-Offset=36m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-99 Oil Recovery Factor ZIGZAG
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60 VD=5m-Offset=0m ZIGZAG-Offset=12m ZIGZAG-Offset=18m ZIGZAG-Offset=24m ZIGZAG-Offset=30m ZIGZAG-Offset=36m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-100 Steam Oil Ratio ZIGZAG
162
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
10e+5
80e+4
60e+4
40e+4
20e+4
00e+0
VD=5m-Offset=0m ZIGZAG-Offset=12m ZIGZAG-Offset=18m ZIGZAG-Offset=24m ZIGZAG-Offset=30m ZIGZAG-Offset=36m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016 Time (Date)
Figure 5-101 Steam Chamber Volume ZIGZAG
5365 Multi-Lateral Producer
For the thin reservoirs of Lloydminster type due to its potential for much higher heat
loss and consequently high cSOR the conventional SAGD is considered uneconomical
In order to access more of the heated mobilized bitumen and increase the productivity of
a well the productive interval of the wellbore can be increased via well completion in the
form of multi-lateral wells Multi lateral wells are expected to provide better reservoir
coverage than horizontal wells and they can extend the life of projects The multi-lateral
producer was numerically simulated and compared against the base case The multishy
lateral producer has 10 legs each has 50m length The producer is located at the same
depth of the injector and with an offset of 6m The results of the Multi-Lateral producer
are presented in Figure 5-102 5-103 5-104 and 5-105 Itrsquos performance is compared
against the most promising well pattern that was explored in earlier sections
163
Oil
Rat
e SC
(m3
day)
0
20
40
60
80
100
120
140
160
180 Multi-Lateral-Offset=6m VD=0m-Offset=30m 3VW-VD=0m-Offset=42m C-SAGD-Offset=42m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-102 Oil Production Rate Comparison
Oil
Rec
over
y Fa
ctor
SC
TR
0
15
30
45
60
75
90 Multi-Lateral-Offset=6m VD=0m-Offset=30m 3VW-VD=0m-Offset=42m C-SAGD-Offset=42m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-103 Oil Recovery Factor Comparison
164
Stea
m O
il R
atio
Cum
SC
TR (m
3m
3)
00
10
20
30
40
50
60
70 Multi-Lateral-Offset=6m VD=0m-Offset=30m 3VW-VD=0m-Offset=42m C-SAGD-Offset=42m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-104 Steam Oil Ratio Comparison
Stea
m C
ham
ber V
olum
e SC
TR (m
3)
00e+0
20e+4
40e+4
60e+4
80e+4
10e+5
12e+5 Multi-Lateral-Offset=6m VD=0m-Offset=30m 3VW-VD=0m-Offset=42m C-SAGD-Offset=42m ZIGZAG-Offset=42m
2009 2010 2011 2012 2013 2014 2015 2016
Time (Date)
Figure 5-105 Steam Chamber Volume Comparison
165
The Multi-Lateral producer is able to sweep off the heavy oil in 4 years at a RF of
67 and cSOR of 56 m3m3 Its performance with respect to ultimate recovery factor and
steam oil ratio is weaker than the rest of optimum patterns The C-SAGD pattern exhibits
the highest RF (81) and at the same time highest cSOR (64 m3m3) Among these
patterns the vertical injectors seems to provide reasonable performance since its recovery
factor is 70 but at a low cSOR value of 52 In addition to the vertical injector
performance the drilling and operation benefits of vertical injector over the horizontal
injector this 3-vertical injector is recommended for future development in Lloydminster
reservoirs
CHAPTER 6
EXPERIMENTAL RESULTS AND
DISUCSSIONS
167
This chapter presents the results and discussions of the physical model experiments
conducted for evaluating SAGD performance in two of Albertarsquos bitumen reservoirs a)
Cold Lake b) Athabasca
The objective of these experiments was to confirm the results of numerical
simulations for the optimum well configuration in a 3-D physical model Two type of
bitumen were used in experiments 1) Elk-Point oil which represents the Cold Lake
reservoir and 2) JACOS bitumen which represents the Athabasca reservoir
Three different well configurations were tested using the two oils I) Classic SAGD
Pattern II) Reverse Horizontal Injector and III) Inclined Injector Each experiment was
history matched using a commercial simulator CMG-STARS to further understand the
performance and behaviour of each experiment A total of seven physical model
experiments were conducted Four experiments used the classic two parallel horizontal
wells configuration which were considered base case tests
The first experiment was used as the base case for the Cold Lake reservoir When the
physical model was designed there were some concerns regarding the initially assumed
reservoir parameters which were applied in the dimensional analysis In the second
experiment the assumed permeability of the model was increased while the same fluids
were used for saturating the model In fact the second experiment was conducted to
examine the scaling criteria discussed in chapter 4
Since a large volume of sand was required in each experiment and re-packing the
model was time consuming there was a thought that perhaps the model can be re-
saturated after each run by oil flooding the depleted model without any cleaning and
opening of the model Therefore the third experiment was run aiming at reducing the
turn-around time for experiments by re-saturating the model The last classic SAGD
pattern was the fifth experiment which uses the same sand as the first experiment but was
saturated using the Athabasca bitumen
Two sets of experiments used the Reverse Horizontal Injector pattern Each test used a
different bitumen while they both were packed with the same AGSCO silica sand Finally
the last experiment used the Inclined Injector pattern using the Athabasca bitumen and
AGSCO sand
168
Table 6-1 presents a summary of all experiments and their relevant initial properties
Table 6-1 Summary of the physical model experiments
Experiment Permeability D
Porosity
Soi
Swi
Viso Ti cp
Well Spacing cm
First 270 3600 8602 1398 29800 5 Second 650 3625 9680 320 29800 5 Third 650 3625 9680 320 29800 5 Fourth 265 3160 8730 1270 29800 10 Fifth 260 3460 8690 1310 440668 10 Sixth 260 3100 8750 1250 440668 10 Seventh 260 3290 8700 1300 440668 5-18
The performance of each experiment was examined based on the injection
production and temperature (steam chamber) data Performance analysis included oil
rate water cut steam injection rate (CWE) cumulative Steam Oil Ratio (cSOR)
recovery factor Water Cut (WCUT) and steam chamber contour maps The contour
maps were plotted to observe the shape and size of steam chamber at various times of
each test The chamber volume profile for each experiment was calculated using
SURFER 90 software which is powerful software for contouring and 3D surface
mapping To obtain a representative chamber volume every single temperature reading
of the thermocouples was imported into the SURFER at specific pore volumes injected
(PVinj) time thereafter the chamber volume which was enclosed by steam temperature
was calculated The final step in the analysis was matching the production profile of each
experiment using a numerical simulation model CMG-STARS
61 Fluid and Rock Properties Two types of packing material either glass beads or sand were used to create a
porous medium inside the model The glass beads were of A-130 size and provided a
permeability of 600-650 D The sand was the AGSCO 12-20 mesh sand with a
permeability of 250-290 D and a porosity of 31-34 The porosity and permeability of
AGSCO 12-20 was measured in the apparatus displayed in Figure 4-2 The sand-pack
was prepared in a 68 cm long stainless steel tube to conduct the permeability
measurements at higher rates The measured points are shown in Figure 6-1 in forms of
the flow rate versus pressure drop and the slope of the fitted straight line is the
permeability According to the slope of the best fit line to the experimental data the
169
permeability of the AGSCO 12-20 was 262 D with the associated porosity of 33 The
AGSCO 12-20 was used in the last five experiments The porosity associated with the
AGSCO 12-20 sand was measured at the start of each run in the 3-D physical model and
it varied between 31-34 Table 6-1 lists the measured values of porosities for each
physical model run It is assumed that the permeability would be similar when the same
sand is packed into the physical model and the resulting porosity in the model is not too
different from that in the linear sand-pack
The objective of this study was aimed at experimental evaluation of the optimum well
configurations on Cold Lake and Athabasca type of reservoirs Hence two heavy oils
were obtained Elk Point heavy oil provided by Husky Energy and the Athabasca
bitumen provided by JACOS The viscosity of both heavy oils was measured using the
HAAKE viscometer described in chapter 4 The viscosity was measured at temperatures
of 25-70 ordmC To estimate a full range of viscosity vs temperature the Mehrotra and
Svercek viscosity correlation [93] was used to honor the measured viscosities of both
oils Figure 6-2 and 6-3 show the viscosity-temperature variation for Elk-Point and
Athabasca bitumen respectively The oil density at room temperature of 21 ordmC was 987
and 1000 kgm3 for Elk Point and JACOS oil respectively
y = 26222x
R2 = 09891
0
10
20
30
40
50
60
70
80
0 005 01 015 02 025 03
∆PL psicm
QA
ccmincm
2
Measured
Linear Regression
Figure 6-1 Permeability measurement with AGSCO Sand
170
1
10
100
1000
10000
100000
0 50 100 150 200 250 300
Measured Data
Mehrotras Corelation
Temperature degC
Viscosity
cp
Figure 6-2 Elk-Point viscosity profile
1
10
100
1000
10000
100000
1000000
0 50 100 150 200 250 300
Temperature C
Visco
cp
Measured Date
Mehrotra Correlation
Figure 6-3 JACOS Bitumen viscosity profile
171
62 First Second and Third Experiments 621 Production Results
The first experiment was conducted to attest the base case performance in Cold Lake
type of reservoir Its well configuration was the classic 11 ratio which is a horizontal
injector located above a horizontal producer The vertical distance between the horizontal
well-pair was 5 cm This vertical distance was an arbitrary number but it is geometrically
similar to the 5 m inter-well distance in 25 m thick formation The model was packed
using AGSCO 12-20 mesh sand and saturated with the Elk-Point oil (at irreducible water
saturation) using the procedure described in Chapter 4 In order to fully saturate the
model ~195 kg of heavy oil was consumed which lead to initial oil saturation of ~86
The saturation step took 12 days to complete
The second experiment used the same configuration and vertical inter-well distance
However instead of AGSCO 12-20 mesh sand A-130 size glass beads were used to pack
the model These glass beads provided a permeability of 600-650 D
The third experiment was a repeat of second one and it was intended to test the
feasibility of re-saturating the model using the Elk-Point oil Unfortunately the re-
saturating idea was not successful and the results were rather discouraging The third
experimentrsquos results were compared against the second experiment The first and second
experiments are compared using the oil production rate cSOR WCUT and recovery
factor in Figures 6-4 6-5 6-6 and 6-7
The oil rate in the first experiment remains mostly in a plateau between 3 to 5 ccmin
following a short-lived peak of 11 ccmin It shows another peak near the end that is
related to blow-down Compared to this the maximum oil rate in the second experiment
is much higher and the rate stays in vicinity of 15 ccmin for most of the run As shown in
Figure 6-4 the oil rate in the second experiment is about 3 times the rate in the first
experiment
The first experiment was run continuously for 27 hours The oil rate reached a peak at
~1 hr which was due to accumulation of heated oil above the producer as a result of
initial attempt for steam trap control The first steam breakthrough happened after 10 min
of steam injection During the run we attempted to keep 10 ordmC of steam trap over the
production well by tracking the temperature profile of the closest thermocouple However
172
controlling the steam trap by manually adjusting the production line valve was a tricky
process which contributed to production rate fluctuations
The water-cut (WCUT) in first experiment stabilized at 65-70 during the first 10
hours of the test The chamber at this time was expanding in the lateral directions and
along the wells but it had already reached to the top of the model In fact at 02 PVinj (5
hours) the steam had touched the top of the model and it had started transferring heat to
the environment through the top wall which increased the heat loss and caused more
steam condensation At 02 PVinj the WCUT displays a small increase but the major
change occurs at 10 hours when the chamber is fully developed at the top and the heat
loss increases It caused the WCUT to stabilize at a higher level of ~80
After 25 hours of steam injection first experiment was stopped and the production
well was fully opened The objective was to utilize the amount of heat that was
transferred to the model and the rock
The comparison of the cSOR for both experiments is shown in Figure 6-5 The cSOR
of the second experiment increased up to 15 cccc at about 01 PVinj and dropped
sharply down to 05 at 02 PVinj while the oil rate increases during this period The cSOR
remained then remained at ~07 cccc up to end of second experiment The explanation
for the sharp increase in oil rate is the production of collected oil above the production
well as the back pressure on the production well was reduced in controlling the sub-cool
temperature
The cSOR in the first experiment is roughly three times higher than the cSOR in the
second experiment Figure 6-7 shows a comparison of the recovery factor for both
experiments Again the second experiment shows vastly superior performance
Figure 6-4 6-5 6-6 and 6-7 show that the formation permeability is a critically
important parameter In fact the only difference between the two results is the impact of
the higher permeability which was about 250 times higher in the second run
173
0
5
10
15
20
25
0 5 10 15 20 25 30 Time hr
Oil
Rat
e c
cm
in
First Experiment Second Experiment
Figure 6-4 Oil Rate First and Second Experiment
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30 Time hr
cSO
R c
ccc
First Experiment Second Experiment
Figure 6-5 cSOR First and Second Experiment
174
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 Time hr
WC
UT
First Experiment Second Experiment
Figure 6-6 WCUT First and Second Experiment
0
5
10
15
20
25
30
35
40
45
0 5 10 15 20 25 30 Time hr
RF
First Experiment Second Experiment
Figure 6-7 RF First and Second Experiment
175
The second and third experiments are compared using oil rate cSOR WCUT and
recovery factor in Figures 6-8 6-9 6-10 and 6-11 The production profile of second and
third experiments is totally different The maximum oil rate oil rate plateau cSOR
WCUT and RF of both experiments are not equal and do not even follow the same trend
These results lead to the conclusion that it is not possible to re-generate the initial
conditions by oil-flooding the post SAGD run model It is possible that due to the heating
and cooling steps in SAGD and the blow-down period in which some of the water
flashes to steam the wettability of sand may have changed and it caused a totally
different production profile The first experiment is considered as the base case for the
well configuration study
0
5
10
15
20
25
30
35
40
45
50
0 2 4 6 8 10 12 14 16 18 20 Time hr
Oil
Rat
e c
cm
in
Second Experiment Third Experiment
Figure 6-8 Oil Rate Second and Third Experiment
176
00
05
10
15
20
25
30
35
0 2 4 6 8 10 12 14 16 18 20 Time hr
cSO
R c
ccc
Second Experiment Third Experiment
Figure 6-9 cSOR Second and Third Experiment
0
10
20
30
40
50
60
70
80
0 2 4 6 8 10 12 14 16 18 20 Time hr
WC
UT
Second Experiment Third Experiment
Figure 6-10 WCUT Second and Third Experiment
177
0
5
10
15
20
25
30
35
40
45
0 2 4 6 8 10 12 14 16 18 20 Time hr
RF
Second Experiment Third Experiment
Figure 6-11 RF Second and Third Experiment
622 Temperature Profiles
Figure 6-12 displays the temperature change with time at different locations along the
injector during the first run D15-D55 thermocouples (See Figure 4-5 for temperature
probe design) are located on top of the injector in a row starting from the heel up to toe of
the injector The chamber grows along the length of the injector but D55 the
thermocouples closet to the toe never reaches the steam temperature D45 which is 6
inches upstream of the toe initially reaches the steam temperature but subsequently cools
down At ~40 min of the injection the increased drainage of cold heavy oil from the heel
zone suppresses the passage of steam to the toe of the injector As a result a sharp
decrease in temperature at D55 is observed which resulted in a drop in the oil
production rate During the entire run the shape of chamber remains inclined towards the
toe of the injector
178
0
20
40
60
80
100
120
0 1 2 3 4 5 Time hr
Tem
pera
ture
C
D15 D25 D35 D45 D55
0
20
40
60
80
100
120
0 4 8 12 16 20 Time hr
Tem
pera
ture
C
D15 D25 D35 D45 D55
Figure 6-12 Temperature profile along the injector at 5 and 20 hours First Experiment
179
The shape of steam chamber within the model using the recorded temperatures in the
first experiment was determined at 01 02 05 06 and 078 PVinj The model was
examined in 5 vertical cross-sections perpendicular the wellbore and in 7 horizontal
layers parallel to the wellbore(A B D D E F and G where G and A layers are located
at the top and bottom of model respectively) The 7th layer (Layer A) is located
somewhere below the production well it does not contribute any interesting result and
therefore is not shown in the plots Figure 6-13 presents the schematic of the 7 layers and
5 cross sections of the physical model
Layer A Layer B
Layer C
Layer D
Layer E Layer F Layer G
Cross Section 1 Cross Section 2
Cross Section 3 Cross Section 4
Cross Section 5
Figure 6-13 Layers and Cross sections schematic of the physical model
The cartoons in Figures 6-14 15 16 17 and 18 represent the chamber extension
across the top six layers Figure 6-19 represents the vertical cross-section which is located
at the inlet of the injector (cross section 1) at 078 PVinj
As the injection starts the injector attempts to deliver high quality steam into the
entire length of the wellbore According to Figure 6-14 the injector fails to provide live
steam at the toe At 2 hours of steam injection which is 01 PVinj the chamber tends to
rise vertically and grow laterally and along the well pairs At 02 PVinj the chamber
above the injector heel has reached the top of the model but it is non-uniform along the
length of well pair After 16 hours of steam injection the chamber is in slanted shape and
the injectors tip has still not warmed up to steam temperature When the steam injection
is about to be stopped (078 PVinj) the chamber growth is continuing in all directions but
it keeps its slanted shape and the injector fails in delivering the steam to the toe Thus the
classic well pattern was not able to provide high quality steam uniformly along the wellshy
180
pair length and consequently created a slanted chamber along the length of the wells with
maximum growth near the heel of the injector Large amount of oil was left behind and
the SAGD process ran at high cSOR Continuing steam injection up to 078 PV did not
make the chamber grow more along the wells
This configuration has been practiced in the industry since SAGD was introduced
however it resulted in high cSOR and a slanted steam chamber with very little reservoir
heating near the toe The question then is whether this problem can be mitigated by using
a modified well configuration
Injector
Producer
Figure 6-14 Chamber Expansion along the well-pair at 01 PVinj
181
Injector
Producer
Injector
Producer
Figure 6-15 Chamber Expansion along the well-pair at 02 PVinj
Figure 6-16 Chamber Expansion along the well-pair at 05 PVinj
182
Injector
Producer
Injector
Producer
Figure 6-17 Chamber Expansion along the well-pair at 06 PVinj
Figure 6-18 Chamber Expansion along the well-pair at 078 PVinj
183
Injector
Producer
Figure 6-19 Chamber Expansion Cross View at 078 PVinj Cross-Section 1
623 History Matching the Production Profile with CMGSTARS
The performance of the first experiment was history matched using the CMGshy
STARS It was attempted to honor the production profile just by changing few reasonable
parameters The thermal conductivity and heat capacity of the model frame (made of
Phenolic resin) for the heat loss purpose was taken as wood thermal properties which was
465E-1 J(cmminoC) and 765 J(cm3oC) respectively These thermal properties
control the heat loss from overburden and under-burden The permeability and porosity
of the model were 240 D and 034 respectively The viscosity profile was the same as the
one presented on Figure 6-2 The relative permeability to oil gas and water which lead
to final history match are provided in Figure 6-20 The end points to water gas and oil
were assumed to be 1 The results of match to oil water and steam injection profile are
presented in Figure 6-21 22 and 23 respectively It should be noted that the initial
constraint on the producer was the oil rate while the second constraint was steam trap
The Injector constraint was set as injection temperature with the associated saturation
pressure
184
It is evident that the numerical model match of the experimental data is reasonable
However another result that needs to be looked into is the chamber volume As discussed
earlier the chamber volume was calculated using thermocouple readings The results were
compared against the chamber volume reported by STARS in Figure 6-24 The match is
reasonable during most the experiment except the last point of water production profile at
078 PVinj At 22 hours when the oil rate has a sharp increase the numerical model is
not able to honor the production profile which leads to a mismatch in chamber volume as
well
Figure 6-20 Water OilGas Relative Permeability First Experiment History Match
185
140 6000
120
100
80
60
40
20
00
Experimental Result-Oil Rate History Match-Oil Rate Experimental Result-Cum Oil History Match-Cum Oil
5000
4000
3000
2000
1000
0
Wat
er R
ate
SC (c
m3
min
)O
il R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
C
umul
ativ
e O
il SC
(cm
3)
0 4 8 12 16 20 24 28 Time (hr)
Figure 6-21 Match to Oil Production Profile First Experiment
28 14000
24
20
16
12
8
4
0
Experimental Result-Water Rate History Match-Water Rate Experimental Result-Cum Water History Match-Cum Water
12000
10000
8000
6000
4000
2000
0 0 4 8 12 16 20 24 28
Time (hr)
Figure 6-22 Match to Water Production Profile First Experiment
186
Wat
er R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
0
5
10
15
20
25
30
0
3000
6000
9000
12000
15000
18000
Experimental Result-Steam (CWE) Rate History Match-Steam (CWE) Rate Experimental Result-Cum Steam (CWE) History Match-Cum Steam (CWE)
0 4 8 12 16 20 24 28 Time (hr)
Figure 6-23 Match to Steam (CWE) Injection Profile First Experiment
Stea
m C
ham
ber V
olum
e SC
TR (c
m3)
0 4 8 12 16 20 24 28 0
500
1000
1500
2000
2500
3000
3500
4000 Experimental Result History Match
Time (hr)
Figure 6-24 Match to Steam Chamber Volume First Experiment
187
63 Fourth Experiment 631 Production Results
The classic SAGD pattern in previous experiments was not able to provide high
quality steam at the toe of the injector and create a uniform chamber Therefore the test
ended up with low RF and high cSOR Numerical simulations of Cold-Lake reservoir in
chapter 5 showed that using the Reversed Horizontal Injector may improve the SAGD
process performance As a result the fourth experiment was designed to test the Reversed
Horizontal Injector pattern using the same sand and bitumen as in the first experiment
The vertical distance between the horizontal well-pair was set at 10 cm This vertical
distance was chosen to improve the manual steam trap control by choking the production
with a valve The model was packed using AGSCO 12-20 mesh sand and a total of ~120
kg sand was carefully packed into the model which was gently vibrated during the
packing process The permeability of the packed model was ~260 D The model was then
evacuated and water was imbibed into the model using both pressure difference and
gravity head The water was then displaced by injecting the Elk-Point heavy oil
Approximately 180 kg of heavy oil was consumed which lead to initial oil saturation of
~90
Using the new well pattern the model was depleted in 17 hours with low cSOR The
results of fourth experiments are compared against the first experiment and presented on
Figure 6-25 26 27 and 28
The oil rate fluctuated during the first 3 hours (01 PVinj) of production but then it
started to steadily increase and peaked at 15 ccmin The oil rate then fell to a high
plateau at 11 ccmin which lasted for almost 5 hours Subsequently the oil rate dropped
down to 6 ccmin at 11 hours (03 PVinj) which is nearing the wind down stage The
fluctuation of oil rate before 01 PVinj is mostly due to the upward chamber growth
which creates counter current steam vapor and condensate-heated oil flow After 02
PVinj the chamber is almost stable and it has reached the top and is growing sideways
This results in increasing and stable oil rate As shown in Figure 6-25 changing the well
configuration increases the oil rate almost 3 times higher than the base case (first
experiment) oil rate In addition the fourth experiment depletes the reservoir at higher
cumulative oil volumes much faster (18 hours comparing to 27 hours) than the first
188
experiment It should be kept in mind that this improvement is due to the well
configuration only the permeability and oil viscosity were kept constant in both
experiments
The first steam breakthrough happened after 20 min of steam injection During the
run time we tried to keep 10 ordmC of steam trap over the production well by tracking the
temperature profile of the closest thermocouple The steam trap control was a difficult
task during the chamberrsquos upward growth however once the chamber reach to the top of
the model it was really smooth and easy
The cSOR in the fourth experiment stabilized at ~1 cccc after a sharp rise at early
time of production Comparing the cSOR profile of the first and fourth experiments it
can be concluded that not only the oil rate is 3 times higher in fourth experiment but also
the cSOR is nearly 3 times lower which makes the Reversed Horizontal Injector pattern
doubly successful and a very promising option for future SAGD projects
In the fourth experiment only half of the total produced liquid was water The WCUT
of fourth experiment remained at 40-60 during the entire test period
Figure 6-28 compares the RF of the first and fourth experiments Fourth experiment
was able to produce slightly higher than 50 of OOIP in 17 hours which demonstrate
that the Reversed Horizontal Injector is able to deplete the reservoir much faster than the
classic SAGD pattern and its final RF at the same time is much higher
632 Temperature Profiles
The temperature profile along the injector well is presented in Figure 6-29 Five
thermocouple points of D31-D35 which are located on the injector were chosen to
validate the steam injection homogeneity along the injector It can be seen that steam has
been successfully delivered throughout the entire length of injector after 6 hours all
thermocouples show temperatures at or above 100 oC At 05 hrs a sharp temperature
decrease occurred at the toe of the injector which resulted from the steam trap control
procedure and imposing some extra back pressure on the production well Figure 6-29
brings out a clear message Reverse Horizontal Injector successfully delivers live steam
throughout the entire length of injector
189
0
2
4
6
8
10
12
14
16
0 5 10 15 20 25 30 Time hr
Oil
Rat
e c
cm
in
First Experiment Fourth Experiment
Figure 6-25 Oil Rate First and Fourth Experiment
0
1
2
3
4
5
6
7
8
0 5 10 15 20 25 30 Time hr
cSO
R c
ccc
First Experiment Fourth Experiment
Figure 6-26 cSOR First and Fourth Experiment
190
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 Time hr
WC
UT
First Experiment Fourth Experiment
Figure 6-27 WCUT First and Fourth Experiment
0
10
20
30
40
50
60
0 5 10 15 20 25 30 Time hr
RF
First Experiment Fourth Experiment
Figure 6-28 RF First and Fourth Experiment
191
0
20
40
60
80
100
120
0 1 2 3 Time hr
Tem
pera
ture
C
D31 D33 D35 D37 D39
0
20
40
60
80
100
120
0 2 4 6 8 10 12 14 16 Time hr
Tem
pera
ture
C
D31 D33 D35 D37 D39
Figure 6-29 Temperature profile along the injector at 3 and 16 hours Fourth Experiment
192
In order to analyse the 3-D growth of the chamber along and across the well-pair the
chamber expansions along the well-pair were determined at 01 02 03 04 and 05
PVinj in different layers As before the model was partitioned into 5 vertical cross-
sections along the wellbore and 7 horizontal layers (A B D D E F and G where G and
A layers are located at the top and bottom of model respectively) Figures 6-30 31 32
33 and 34 present the chamber extension across each layer Figure 6-35 presents the
vertical cross-section which is located at the inlet of the injector at 05 PVinj
Injector Producer
Figure 6-30 Chamber Expansion along the well-pair at 01 PVinj
193
Injector Producer
Figure 6-31 Chamber Expansion along the well-pair at 02 PVinj
Injector Producer
Figure 6-32 Chamber Expansion along the well-pair at 03 PVinj
194
Injector Producer
Figure 6-33 Chamber Expansion along the well-pair at 04 PVinj
Injector Producer
Figure 6-34 Chamber Expansion along the well-pair at 05 PVinj
195
According to Figures 6-30-34 the Reversed Horizontal Injector is able to introduce
steam along the entire well length Even at early steam injection period (01 PVinj) the
entire injector length is warmed up close to the injection temperature At this point the
steam chamber just needs to grow laterally and vertically After 02 PVinj the steam
chamber almost approached the side walls leading to the maximum oil rate and
minimum WCUT Sometimes after 03 PVinj when the chamber hits the side walls the
oil rate started to decrease which leads to higher WCUT As per Figures 6-31 and 6-32
the chamber grows somewhat faster at the heel of producer where the steam broke
through initially but it was controlled by steam trap later on
In chapter 5 it was mentioned that the new pattern is able to create homogenous steam
chamber along the well pairs The plotted temperature contours using the recorded
temperatures confirm that a uniform chamber was created on top of the well pairs This
fact also confirms that a uniform pressure drop existed between the injector and producer
throughout the experiment period which improves the SAGD process efficiency and
leads to higher RF and lower cSOR as shown earlier
Injector
Producer
Figure 6-35 Chamber Expansion Cross View at 05 PVinj Cross Section 1
196
633 History Matching the Production Profile with CMGSTARS
The performance of the fourth experiment was history matched using the CMGshy
STARS As in the first experiment few parameters were changed to get the best match of
the experimental results The thermal conductivity and volume capacity of the model
frame (made of Phenolic resin) was the same as in the first experiment The permeability
and porosity of the model were 260 mD and 031 respectively The viscosity profile is the
same as the one presented on Figure 6-2 The relative permeability to oil gas and water
which lead to final history match are provided on Figure 6-36 The end point to water
gas and oil were 075 035 and 1 respectively The results of match to oil water and
steam injection profile are presented on Figure 6-37 38 and 39 It has to be noted that
the initial constraint on producer was the oil rate while the second constraint was steam
trap The Injector constraint was set as injection temperature with the associated
saturation pressure
It seems that the numerical model matches the experimental data reasonably well
The last result that needs to be looked into is the chamber volume As discussed earlier
the chamber volume was calculated using thermocouple readings The results were
compared against the chamber volume reported by STARS in Figure 6-40 The match is
reasonable during the entire experiment except for the last point which is 05 PVinj The
difference can be due to possible error in simulation of the heat loss from the side walls
of the model which becomes a larger factor near the end
197
Figure 6-36 Water OilGas Relative Permeability Fourth Experiment History Match
198
Oil
Rat
e SC
(cm
3m
in)
Cum
ulat
ive
Oil
SC (c
m3)
0
4
8
12
16
20
0
2000
4000
6000
8000
10000 Experimental Result-Oil RateHistory Match-Oil Rate Experimental Result-Cum OilHistory Match-Cum Oil
0 4 8 12 16 20
Time (hr)
Figure 6-37 Match to Oil Production Profile Fourth Experiment
Wat
er R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
0
3
6
9
12
15
0
2000
4000
6000
8000
10000 Experimental Result-Water Rate History Match-Water RateExperimental Result-Cum Water History Match-Cum Water
0 4 8 12 16 20
Time (hr)
Figure 6-38 Match to Water Production Profile Fourth Experiment
199
Wat
er R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
0
3
6
9
12
15
18
0
2000
4000
6000
8000
10000
12000 Experimental Result-Steam (CWE) Rate History Match-Steam (CWE) Rate Experimental Result-Cum Steam (CWE)History Match-Cum Steam (CWE)
0 4 8 12 16 20
Time (hr)
Figure 6-39 Match to Steam (CWE) Injection Profile Fourth Experiment
Stea
m C
ham
ber V
olum
e SC
TR (c
m3)
0
1000
2000
3000
4000
5000
6000
7000
8000 Experimental Result History Match
0 4 8 12 16 20
Time (hr)
Figure 6-40 Match to Steam Chamber Volume Fourth Experiment
200
64 Fifth Experiment 641 Production Results
Part of current study was aimed at optimizing the well configuration for Athabasca
reservoir Numerical simulations were conducted and promising well configurations were
identified It was considered desirable to test some of those configurations in the 3-D
physical model
To start with a simple 11 pattern was needed to establish an experimental base case
for the Athabasca study Hence the fifth experiment was conducted to build the base case
for further comparisons The pattern includes only 2 horizontal wells one located near
the bottom of the physical model and the second well which operates as an injector was
located 10 cm above the producer The larger inter-well distance of 10 cm was used to
overcome difficulties encountered in the manual steam trap control by manipulating the
production line valve
The model was packed and saturated using the procedure described earlier A total of
~120 kg sand was packed into the model and the permeability of the porous packed
model was ~260 D The bitumen used for saturating the model was provided by JACOS
from Athabasca reservoir In order to fully saturate the model ~216 kg of bitumen was
consumed which gave the initial oil saturation of ~87 The saturation step took 20 days
to be completed The fifth experiment was completed by injection of steam into the
model via injector for 20 hrs The oil rate cSOR WCUT and RF are presented in
Figures 6-41 42 43 and 44
The first steam break-through occurred approximately after one hour of steam
injection Controlling the steam break-through was really difficult throughout the entire
experiment once the back pressure on the production valve was reduced in order to let
more oil come out the steam jumped into the production well As a result the back
pressure had to be increased which caused the liquid level to raise in vicinity of the
production well The steam trap control never became fully stable throughout the
experiment and was one of the biggest challenges during the test Most of the fluctuations
in oil production rate were due to steam trap control process
The cSOR in this experiment had a sharp rise similar to the previous SAGD tests
and thereafter it stabilized at ~2 cccc The sharp rise is due to vertical chamber growth
201
At 05 PVinj (~15 hours) when the entire injector starts getting live steam the cSOR
drops sharply which explains the sharp increase in oil rate and high slope WCUT
reduction At 055 PVinj (163 hours) the steam broke through and to control the live
steam production higher back pressure was imposed on the producer which caused a
sharp decrease in oil rate and a pulse in cSOR and WCUT profile However after a while
it was stabilized and the oil rate went back on the track again and the cSOR became
stable
Water production in the fifth experiment was similar to the first test According to
Figure 6-43 almost 60 of the total produced liquid was water which is the expected
behavior in SAGD The RF profile is presented in Figure 6-44 Almost 50 of the
bitumen was produced after 20 hours
642 Temperature Profile
Figure 6-45 displays the temperature profile along the injector D15-D55
thermocouples (Figure 4-5) are located in a row starting from the heel up to toe of
injector At about 20 min of production the chamber was collapsing down and the
temperature was decreasing due to low injectivity the steam was not able to penetrate
into the bitumen saturated model Consequently a sharp drop in the temperature profile
was created which resulted in reduced oil production rate as well The back pressure was
removed completely to facilitate steam flow and this allowed the steam to move again
However the chamber along the producer and injector was unstable for the first 3 hours
of production The Chamber formed at the heel (about 25 of the injector length) in one
hour and the temperature near the heel was stable to the end of this test but the rest of the
wellbore had difficulties in delivering steam into the model After 10 hours the middle of
the injector reached the steam temperatures while the rest of the wellbore (the 25th of
injector length covering D45 and D55) got warmed up to steam temperature only after 16
hours had passed from the beginning the test It can be seen that these temperature and
chamber volume fluctuations result in oil production scatter
202
0
2
4
6
8
10
12
14
16
18
20
0 4 8 12 16 20 Time hr
Oil
Rat
e c
cm
in
Fifth Experiment
Figure 6-41 Oil Rate Fifth Experiment
00
05
10
15
20
25
30
0 4 8 12 16 20 Time hr
cSO
R c
ccc
Fifth Experiment
Figure 6-42 cSOR Fifth Experiment
203
0
10
20
30
40
50
60
70
80
90
0 4 8 12 16 20 Time hr
WC
UT
Fifth Experiment
Figure 6-43 WCUT Fifth Experiment
0
10
20
30
40
50
60
0 4 8 12 16 20 Time hr
RF
Fifth Experiment
Figure 6-44 RF Fifth Experiment
204
0
20
40
60
80
100
120
0 1 2 3 4 5 Time hr
Tem
pera
ture
C
D15 D25 D35 D45 D55
0
20
40
60
80
100
120
0 4 8 12 16 20 Time hr
Tem
pera
ture
C
D15 D25 D35 D45 D55
Figure 6-45 Temperature profile along the injector at 5 and 20 hours Fifth Experiment
205
In order to analyse the 3-D growth of the chamber along and across the well-pair the
chamber expanse along the well-pair were determined at 01 02 03 04 05 and 065
PVinj for different layers As in the previous experiments the model was partitioned into
5 vertical cross-sections along the well-pairs and 7 horizontal layers (A B D D E F
and G where G and A layers are located at the top and bottom of model respectively)
Figures 6-46 47 48 49 50 and 51 present the chamber extension across each layer
(only 6 layers are shown) Figure 6-51 represents the cross-section which is located at the
heel of the injector at 05 PVinj
Injector
Producer
Figure 6-46 Chamber Expansion along the well-pair at 01 PVinj
206
Injector
Producer
Injector
Producer
Figure 6-47 Chamber Expansion along the well-pair at 02 PVinj
Figure 6-48 Chamber Expansion along the well-pair at 03 PVinj
207
Injector
Producer
Injector
Producer
Figure 6-49 Chamber Expansion along the well-pair at 04 PVinj
Figure 6-50 Chamber Expansion along the well-pair at 05 PVinj
208
Injector
Producer
Figure 6-51 Chamber Expansion along the well-pair at 065 PVinj
Injector
Producer
Figure 6-52 Chamber Expansion Cross View at 065 PVinj Cross Section1
209
Figures 6-46 to 6-51 show that a major shortcoming of the classic pattern is uneven
injection of steam along the injector length which results in a slanted steam chamber
The injector is not able to supply live steam at the toe most of the steam gets injected
near the heel which causes an issue in steam trap control and lower productivity because
the zone near the toe does not get heated At the end of the physical model experiment
the process produced a slanted chamber which gave a reasonable RF but at higher cSOR
643 Residual Oil Saturation
The model was partitioned into three layers each had a thickness of approximately 8
cm and each layer comprised 9 sample locations Figure 6-53 presents the schematic of
the sample locations on each layer
1 2 3
4 5 6
7 8 9
50 cm
8 cm 50 cm
Figure 6-53 Sampling distributions per each layer of model
The sand samples taken from these locations were analyzed in the Dean Stark
apparatus The volumetric balance on the taken samples extracted oil and water and the
cleaned dried sand was used to calculate the residual oil and water saturations Using the
porosity initial oil saturation and residual oil saturation the φΔSo parameter can be
calculated In section 444 a range of 02-03 was assumed for the model while in a real
reservoir this number would typically be 015-02 Figure 6-54 presents the φΔSo of the
middle layer where the injector is located and the chamber has grown throughout the
entire layer
The injector is located at X=255 cm and enters into the model at Y=0 cm At X=255
cm the maximum value of φΔSo is 233 which is located at the heel of the injector where
most of steam was injected and resulted in the minimum residual oil saturation Along the
length of the injector the residual oil saturation increases which cause a decreasing trend
in φΔSo value
210
85 255
425
425
255
85
222 233
220
239
223
267
217
200
251
10
12
14
16
18
20
22
24
26
28
φΔS
o
X cm
Y cm
Mid Layer
Figure 6-54 φΔSo across the middle layer fifth experiment
The average φΔSo of the middle layer stays in the range of 02-03 which was
assumed in the dimensional analysis section The variations in the values of φΔSo are
partly due to the process performance and partly due to the experimental errors There
can be some unevenness in the porosity due to the packing inhomogeneity and the
calculation of residual saturation by extraction has some associated error There are two
higher values of residual oil saturations on the two corners close to the heel of injector
which may be interpreted as the error associated with the measurement technique The
same plot was generated for the top layer in Figure 6-55 In figure 6-55 the residual oil
saturation keeps the expected trend parallel to the injector at 85 and 255 cm on X-axis
however the trend fails on 425 cm location on X-axis Again in one corner close to the
injectorrsquos heel the residual oil saturation is unexpectedly high The average residual
saturation of the top layer still falls in the expected range listed the dimensional analysis
section
211
85 255
425
425
255
85
220 224
210 211 212
228
197 200
244
10
12
14
16
18
20
22
24
26
φΔS
o
X cm
Y cm
Top Layer
Figure 6-55 φΔSo across the top layer fifth experiment
644 History Matching the Production Profile with CMGSTARS
In order to analyze and study the performance of the fifth experiment under numerical
simulation its production profile was history matched using the CMG-STARS Only the
relative permeability curves porosity permeability and the production constraint were
changed to get the best match of the experimental results The thermal conductivity and
heat capacity of the model frame (made of Phenolic resin) was the same as in the
previous experiment The permeability and porosity of the model were 260 mD and 034
respectively The viscosity profile was the same as the one presented on Figure 6-3 which
is the measured and modeled viscosity profile for Athabasca bitumen The relative
permeability to oil gas and water which gave the final history match is provided in
Figure 6-56 The end points to water gas and oil were assumed to be 03 014 and 1
respectively The results of the match to oil water and steam production profile are
presented in Figure 6-57 58 and 59 It should be noted that the initial constraint on
producer was the oil rate while the second constraint was steam trap The Injector
constraint was set as injection temperature with the associated saturation pressure
212
It seems that the numerical model matches the experimental data quite well However
one last result that needs to be looked into is the chamber volume As discussed earlier
the chamber volume was calculated using thermocouple readings The results were
compared against the chamber volume reported by STARS in Figure 6-60 This match is
a bit off during the entire experiment Since there were too many issues in steam trap
control and the chamber was expanding erratically during the experiment it was not
surprising that the chamber volume history was not well-matched
Figure 6-56 Water OilGas Relative Permeability Fifth Experiment History Match
213
Oil
Rat
e SC
(cm
3m
in)
Cum
ulat
ive
Oil
SC (c
m3)
00
50
100
150
200
0
2000
4000
6000
8000
10000 Experimental Result Oil RateHistory Match Oil Rate Experimental Result Cum OilHistory Match Cum Oil
0 200 400 600 800 1000 1200 Time (min)
Figure 6-57 Match to Oil Production Profile Fifth Experiment
Wat
er R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
0
6
12
18
24
30
0
3000
6000
9000
12000
15000 Experimental Result Water Rate History Match Water Rate Experimental Result Cum WaterHistory Match Cum Water
0 200 400 600 800 1000 1200 Time (min)
Figure 6-58 Match to Water Production Profile Fifth Experiment
214
Wat
er R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
0
7
14
21
28
35
42
0
3000
6000
9000
12000
15000
18000 Experimental Result Steam (CWE) RateHistory Match Steam (CWE) Rate Experimental Result Cum Steam (CWE)History Match Cum Steam (CWE)
0 200 400 600 800 1000 1200 Time (min)
Figure 6-59 Match to Steam (CWE) Injection Profile Fifth Experiment
Stea
m C
ham
ber V
olum
e SC
TR (c
m3)
0
2000
4000
6000
8000 History MatchExperimental Result
0 200 400 600 800 1000 1200 Time (min)
Figure 6-60 Match to Steam Chamber Volume Fifth Experiment
215
65 Sixth Experiment 651 Production Results
The classic SAGD pattern in fifth experiment showed the expected performance of a
11 ratio SAGD well pattern Although it provides commercially viable performance in
the field some of the issues with it are low oil rate not very high RF high WCUT high
cSOR In the physical model experiments it gives very long run time due to slow
drainage rate In addition to these difficulties if the temperature contour maps were
studied carefully the steam chamber is not homogenous and it is slanted along the well
pairs
Several numerical simulations that were run on Athabasca reservoir and were
presented in Chapter 5 showed the Reversed Horizontal Injector pattern to be superior to
the classic pattern It was shown that the new pattern is able to improve the performance
of the SAGD process The new well configuration was tested in Cold Lake type of
reservoir in the fourth experiment and it showed large improvement that was
considerably more pronounced than the numerical simulation result Therefore it would
be desirable to test the new well configuration under the Athabasca type of reservoir
conditions as well Hence the sixth experiment was designed to test the Reversed
Horizontal Injector pattern under Athabasca conditions
As in the preceding base case experiment 10 cm vertical inter-well distance was
used The same AGSCO 12-20 mesh sand used to create the porous medium in the
model The permeability and porosity of the porous packed model were ~260 D and 031
respectively In order to fully saturate the model ~180 kg of JACOS bitumen was
consumed which lead to initial oil saturation of ~90 Using the new well pattern the
model was depleted in 13 hours with relatively low cSOR The results of this experiment
is compared against the fifth experiment and presented in Figures 6-61 62 63 and 64
216
0
5
10
15
20
25
0 4 8 12 16 20
Time hr
Oil
Rat
e c
cm
in
Fifth Experiment Sixth Experiment
Figure 6-61 Oil Rate Fifth and Sixth Experiment
00
05
10
15
20
25
30
35
0 4 8 12 16 20 Time hr
cSO
R c
ccc
Fifth Experiment Sixth Experiment
Figure 6-62 cSOR Fifth and Sixth Experiment
217
0
10
20
30
40
50
60
70
80
90
0 4 8 12 16 20 Time hr
WC
UT
Fifth Experiment Sixth Experiment
Figure 6-63 WCUT Fifth and Sixth Experiment
0
10
20
30
40
50
60
0 4 8 12 16 20 Time hr
RF
Fifth Experiment Sixth Experiment
Figure 6-64 RF Fifth and Sixth Experiment
218
The oil production profile of the sixth experiment is compared against the fifth
experiment in Figure 6-61 The oil rate profile has some fluctuations throughout the
experiment Before 01 PVinj (~3 hours) the steam chamber is growing upward and
laterally which makes the chamber to be somewhat unstable due to the counter current
flow Consequently the liquid production shows fluctuations which can be observed in
Figure 6-61 The oil rate fluctuates between 5 and 10 ccmin The steam chamber reaches
to top of the model somewhere between 01 and 02 PVinj (~45 hours) which leads to a
sharp increase in the oil rate Then the average oil rate somewhat stabilized at 15 ccmin
with a maximum and minimum of 20 and 10 ccmin respectively At 04 PVinj where the
chamber hits the adjacent sides the oil rate gets another jump but since the chamber
cannot spread anymore and extra heat loss occurs from the sidewalls the oil rate drops
down at 05 PVinj (11 hours) A part of the oil rate fluctuation originated from the
manual control of the steam trap using the valve adjustments The Reverse Horizontal
Injector displays a dramatic improvement where the oil rate of this experiment is nearly
twice that of the fifth experiment (which used the classic pattern)
The first steam breakthrough happened after 50 min of steam injection During the
run we tried to keep 10 ordmC of steam trap over the production well by tracking the
temperature profile of the closest thermocouple Since the pressure drop along the well-
pair was almost uniform the steam trap control was relatively simple In this experiment
the cSOR increased sharply during the rising chamber phase of the process It then
decreases smoothly to ~15 cccc A comparison of the cSOR profiles of the fifth and the
sixth experiments is provided in Figure 6-62 The sixth experiment displays lower cSOR
almost half of the fifth experiment The WCUT in sixth experiment is 50-60 and is
compared against the fifth experiment in Figure 6-63 It can be seen that the well
configuration in sixth experiment yields less heat loss which caused the WCUT to be
lower compared to the fifth experiment Figure 6-64 demonstrates the RF of these two
experiments According to Figure 6-64 the Reversed Horizontal Injector can provide
higher RF in shorter period compared to the classic well pattern In the sixth experiment
after 13 hours 55 of the OOIP had been produced while at the same time only 25 of
OOIP had been produced by the classic pattern in the fifth experiment The combination
of oil rate cSOR WCUT and RF profile makes the Reversed Horizontal Injector a very
219
promising replacement for the classic pattern in SAGD process in Athabasca type of
reservoir
652 Temperature Profiles
Figure 6-65 displays the temperature profiles at the injector for the first 4 and first 14
hours of steam injection D31-D39 thermocouples (Figure 4-5) are located in a row
starting from the heel up to toe of the injector The first four points get to steam
temperature in less than one hour The last point which is located at the toe of the injector
warmed up to steam temperature after 2 hours This made the steam trap control very
easy since the steam broke through to the production well at the producerrsquos toe instead of
its heel
The chamber growth in the model was studied by determining the chamber
expansions in different layers at 01 02 03 04 05 and 06 PVinj Out of the 7 layers
(A B D D E F and G where G and A layers are located at the top and bottom of model
respectively) only 6 layers are included in the plots since the 7th layer (Layer A) is
located somewhere below the production well and does not show any interesting result
Figures 6-66 67 68 69 70 and 71 represent the chamber extension across each layer
Figure 6-72 represent the cross-section which is located at the inlet of the injector at 06
PVinj
At 01 PVinj the chamber has just formed around the injector in the E layer which is
located above the injector At 02 PVinj the chamber hit the top of the model and it
started growing only laterally At 03 PVinj it approached the vicinity of the side walls
but it is at 04 PVinj when the steam chamber reaches the side walls From 04 PVinj till
06 PVinj the steam chamber grows downward on the side walls which is reflected in
the chamber development on C and B layers
According to Figures 6-66 to 6-71 the Reversed Horizontal Injector pattern delivers
high quality steam throughout the injector soon after the steam injection starts It
successfully develops a uniform chamber laterally while it continuously supplies the live
steam at the toe of the injector This results in low cSOR and WCUT while the oil rate
and RF are dramatically higher
220
0
20
40
60
80
100
120
0 1 2 3 4 Time hr
Tem
pera
ture
C
D31 D33 D35 D37 D39
0
20
40
60
80
100
120
0 2 4 6 8 10 12 14 Time hr
Tem
pera
ture
C
D31 D33 D35 D37 D39
Figure 6-65 Temperature profile along the injector at 4 and 14 hours Sixth Experiment
221
Injector Producer
Figure 6-66 Chamber Expansion along the well-pair at 01 PVinj
Injector Producer
Figure 6-67 Chamber Expansion along the well-pair at 02 PVinj
222
Injector Producer
Figure 6-68 Chamber Expansion along the well-pair at 03 PVinj
Injector Producer
Figure 6-69 Chamber Expansion along the well-pair at 04 PVinj
223
Injector Producer
Figure 6-70 Chamber Expansion along the well-pair at 05 PVinj
Injector Producer
Figure 6-71 Chamber Expansion along the well-pair at 06 PVinj
224
Injector
Producer
Figure 6-72 Chamber Expansion Cross View at 05 PVinj
653 Residual Oil Saturation
As in the fifth experiment the model was partitioned into three layers each has a
thickness of approximately 8 cm and each layer comprised 9 sample locations Figure 6shy
52 presents the schematic of the sample locations on each layer The same methodology
presented in section 643 was followed to calculate φΔSo over each layer of the model
Figure 6-73 presents the φΔSo of the middle layer where the injector is located and
the chamber has grown throughout the entire layer
The injector is located at Y=255 cm and enters into the model at X=50 cm The
average φΔSo over the middle layer is in the range of 12-14 The run time of sixth
experiment was short and compared to the rest of tests and it lead to higher residual oil
saturation over the middle layer At Y=255 cm which is along the length of the injector
the residual oil saturation has a fairly constant values showing a flat trend in φΔSo value
The maximum oil saturation is located on top of the injectorrsquos heel which is right above
the producerrsquos toe in the reversed horizontal injector pattern There are two high values of
residual oil saturations on the two corners close to the toe of injector which may be due to
less depletion near the two corners The same plot was generated for the top layer in
225
Figure 6-74 The distribution of the residual oil saturation over the top layer is more
uniform than the middle layer which means steam was able to sweep out more oil and the
chamber was spread uniformly throughout the entire layer The average residual
saturation of the top layer still falls in the expected range of the dimensional analysis
section
Mid Layer
14
13
12
11
85
255 10
425
136
132
129
126 127
121
131
123
122
Y cm 425 85
255
X cm
φΔS
o
Figure 6-73 φΔSo across the middle layer sixth experiment
226
85 255
425
425
255
85
229 223
253
235
225 237 235
225 222
10
12
14
16
18
20
22
24
26
φΔS
o
X cm
Y cm
Top Layer
Figure 6-74 φΔSo across the top layer sixth experiment
654 History Matching the Production Profile with CMGSTARS
The results of sixth experiment were history matched using CMG-STARS It was
tried to keep the consistency between the sixth and previous numerical models
Therefore the thermal conductivity and heat capacity of the model frame (made of
Phenolic resin) were kept the same as in first fourth and fifth experiments The
permeability and porosity of the model were 260 mD and 031 respectively The viscosity
profile was the same as the one presented on Figure 6-3 The relative permeability to oil
gas and water which lead to final history match are shown in Figure 6-75 The end point
to water gas and oil were assumed to be 017 008 and 1 respectively The results of
match to oil water and steam production profile are presented on Figure 6-76 to 6-78 As
in the previous simulations the initial constraint on producer was the oil rate while the
second constraint was steam trap The Injector constraint was set as injection temperature
with the associated saturation pressure In this case also the numerical model matched
the experimental data reasonably well The match of the chamber volume whose
227
experimental values were calculated using thermocouple readings while the simulated
values were as reported by STARS is shown in Figure 6-79 The match turned out to be
nearly perfect
Figure 6-75 Water OilGas Relative Permeability Sixth Experiment History Match
228
24 12000
20
16
12
8
4
0
Experimental Result Oil RateHistory Match Oil Rate Experimental Result Cum OilHistory Match Cum Oil
10000
8000
6000
4000
2000
0
Wat
er R
ate
SC (c
m3
min
)O
il R
ate
SC (c
m3
min
)
Cum
ulat
ive
Wat
er S
C (c
m3)
C
umul
ativ
e O
il SC
(cm
3)
0 2 4 6 8 10 12 14 Time (hr)
Figure 6-76 Match to Oil Production Profile Sixth Experiment
30 12000
25
20
15
10
5
0
Experimental Result Water Rate History Match Water Rate Experimental Result Cum Water History Match Cum Water
10000
8000
6000
4000
2000
0 0 2 4 6 8 10 12 14
Time (hr)
Figure 6-77 Match to Water Production Profile Sixth Experiment