CO2-EOR Potential of Gravity -Stable CO Injection in … OIL RECOVERY INSTITUTE Shaochang Wo CO...

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E

Shaochang Wo

CO2-EOR Potential of Gravity-Stable CO2 Injection in the Frannie Tensleep Reservoir

Casper, Wyoming July 8-9, 2013

The 3rd Tensleep Workshop of EORI


Outline

• An Overview of the Geological Setting and Production History of the Frannie Field

• OOIP Estimation Based on Stone’s Common-Pool Theory • Pressure Communication among All Tensleep Zones as

Indicated from DST Data and Pressure Buildup Tests • The Effect of Natural Fractures on Reservoir Conformance • Challenges to Achieving Optimum Performance of CO2

Floods in the Frannie Tensleep Reservoir and Its TZ/ROZs • Applicability of Gravity-Stable CO2 Injection at the Frannie

Field • Initial Estimations of Oil Recovery by Gravity-Stable CO2

Injection • Summary


Wyoming Oil & Gas Fields

Powder River Basin

Greater Green River Basin

Bighorn Basin

Wind River Basin Overthrust

Belt

Hanna Basin

Laramie Basin

Jackson Hole

Denver Basin

Shirley Basin

Frannie-Sage Creek Area


Aquifer Water Influx


Frannie Tensleep: Top of A Sand Unit

Oil Pool after Tilting


Southwest Northeast

13o

TZ/ROZ

Main Pay Zone

Illustration of Southwest-Northeast Cross Section at Frannie Field

~9,000 ft

~2,0

00 ft

45o A

~200 ft

B

C D

E

F


A

A

A

B

D

E

F

E

Well Logs and Identified Sand Units in Well #147


0

50,000

100,000

150,000

200,000

250,000

300,000

350,000

1928 1938 1948 1958 1968 1978 1988 1998 2008 2018

Mon

thly

Oil

Prod

uctio

n Ra

te, B

O/m

onth

Frannie Field: Monthly Oil Production Rate

Discovery well Feb. 1928

Total 15 production wells drilled before 1940

122 wells drilled between 1940 ~ 1955

99% water cut In 2011

22 wells drilled between 1955 ~ 1989

Before 1948: produced only from A&B zones After 1948: produced from all zones

Water flooding started in Dec. 1970


Monthly Productions at Frannie Field (after 1978)

Average Water Cut in 2011: 99%


Depth of Tensleep Top 2548 ft Initial Reservoir Pressure NA, est. 1800 psi

Average Core Porosity 17%, Range 9-33% Oil Gravity 25-28.3o API

Average Core Permeability 75 md, Range 0.1-1000 md Bubble Point Pressure (BPP) 58-305 psi

Average Pay Thickness 100 ft Gas Oil Ratio at BPP 33.2-66 SCF/STB

Average Gross Pay 200 ft Est. OOIP in Main Pay Zone 215.7 MMBO

Oil Column 1300 ft Cum. Oil Production 119.1 MMBO

Oil/Water Contact NA, est. 450 ft above sea level Oil Recovery 55.22%

Reservoir Temperature 96o F Well Spacing 10 acre

Primary Drive Mechanism Water and solution gas CO2 MMP Est. 1750 psi

Oil and Reservoir Properties of the Frannie Tensleep


“… The hydrocarbons held within these Phosphoria and Tensleep stratigraphic traps were later released as a consequence of fracturing and faulting associated with Laramide folding, and moved into older Paleozoic reservoir rocks until fully adjusted to anticlinal structure in common pools. Vertical segregation of an original common pool into several separate pools was accomplished in some exceptional fields of the basin either by selective hydrodynamic tilting within the Tensleep zone, by leakage or redistribution of fluids through fault zones, … ”

“Theory of Paleozoic Oil and Gas Accumulation in the Big Horn Basin, Wyoming” by D. S. Stone, 1967, SPE 1883


Frannie Tensleep: Top of A Sand Unit 1

2 3

4 5

6 7

8

9

A

A


Edited from L.B. Curtis, 1954

1 2 3 4 5 6 7 8 9

Mean Oil-Water Contact in the Madison: 1107’ above Sea Level

Tensleep Oil Pool before Tilting



Oil Pool before Tilting



Oil Pool before Tilting

Oil Pool after Tilting

Peak Rate: 1292 BOPD Cum. Oil: 756 MBO

Well 128


AVG. WATER TOTAL POROSITY AVERAGE ORIGINAL OIL

SAND UNIT SATURATION (MATRIX+FRACTURE) AREA NET PAY IN PLACE

fraction fraction acres feet STB

A 0.157 0.176 1636 16 29,538,819 B 0.127 0.191 1636 45 93,366,919 C 0.130 0.185 1636 14 28,038,316 D 0.139 0.175 1636 10 18,748,827 E 0.162 0.168 1636 37 64,816,851 F 0.183 0.155 1636 7 11,030,233

Boi = 1.02

Estimated OOIP of the Frannie Tensleep Oil Pool before Tilting

Total Est. OOIP = 245.5 million STB


Scenarios of OOIP Calculation Est. OOIP Cum. Oil Produced Oil Recovery MMBO MMBO %

OWC at +450' Elevation after Tilting* 215.7 119.1 55.22 OWC at the Sea Level after Tilting* 267.5 119.1 44.52 OWC at +1107' Elevation before Tilting 245.5 119.1 48.51

*data from a 1991 Conoco Report


Available Data from the Frannie Field That Are Used for Assessing Reservoir Connectivity and Fracture Effects

• Well logs • Core description and measurements • DST data • WBH Pressure buildup tests • Tracer tests • Well perforation and workover history • Injection profile tests • Producers’ response to neighboring

injectors


-400

-200

0

200

400

600

800

1000

1200

1400

1600

1/1/1928 6/23/1933 12/14/1938 6/5/1944 11/26/1949 5/19/1955 11/8/1960 5/1/1966

Pres

sure

, psi

g

Frannie Tensleep: Pressure Buildup Tests & DST Data before 1970

Measured Pressure

Pressure corrected to +1200'

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E Frannie Tensleep Reservoir Pressure in June 1936 and June 1937 (data) Pressure Corrected to +1,200’ Datum

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E Frannie Tensleep Reservoir Pressure in October 1960 Pressure Corrected to +1,200’ Datum

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E Frannie Tensleep Reservoir Pressure in April 1967 Pressure Corrected to +1,200’ Datum


Fracture Interpretation of the Southeast Tensleep Outcrop at Alcova Anticline, Wyoming

- Figures copied from Nathaniel Gilbertson & Neil F. Hurley (2005)


Well #147 was drilled and cored in 1988

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E 0.00001

0.0001

0.001

0.01

0.1

1

10

100

1000

10000

0.000001 0.00001 0.0001 0.001 0.01 0.1 1

Frac

ture

Per

mea

bilit

y, D

arcy

Fracture Porosity, fraction

Fracture Permeability as a Function of Fracture Porosity and Width

Kf = ɸf 𝑒2/12

e = 10 micron

50 micron

100 micron

200 micron

1 mm

700 micron

500 micron

300 micron


Frannie Tensleep Wells Have Been Sand Fractured (260 fracture treatments by 1990)


Injection Profile of Well 120

A Sand

B Sand

25%

30%

45%


Injection Profiles of Well 78 with Single or Dual Injection Configuration

B Sand

C Sand

D Sand

E Sand

Single Single Single Single Single Single Dual Dual Dual

Open hole Linered


Challenges to Achieving Optimum Performance of CO2 Floods in the Frannie Tensleep Reservoir

• Lateral and Vertical Conformance Problems because of the Existence of Highly Conductive Natural Fractures and A 200-foot Thick Gross Pay Interval

• Lower Formation Fracture Pressure due to A Relatively Shallow Reservoir; the Depth of the Structure Top at the Frannie Tensleep is about 2548 ft

• Only Near-Miscible CO2 Flooding Will Likely Be Achieved at the Structure Top

• Strong Hydrodynamic Flow • Uncertainty of Current Remaining Oil Distribution in

the Reservoir

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E 0

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0 500 1000 1500 2000 2500 3000 3500

Oil

Reco

very

, %

Pressure, psi

Oil Sample from Well #75; Oil Gravity=26.8 oAPI; Tested at 110 oF

Slim-tube Tests of CO2 Flood on Frannie Tensleep Oil

“Near-Miscibility” Pressure: ~1600 psi Range of Fracturing Pressure


Critical Velocity for Gravity-Stable Gas Injection

Hill (1952)

Dumore (1964)

𝑉𝑐 =2.741𝐾𝐾𝐾𝐾𝐾 𝜌𝑜 − 𝜌𝑔

∅(𝜇𝑜 − 𝜇𝑔)

𝑉𝑐 =2.741𝐾𝐾𝐾𝐾𝐾

∅𝜕𝜌𝜕𝜇 𝑚𝑚𝑚

Vc = Critical velocity, ft/d K = Permeability, Darcy θ = Dip angle, degree φ = Porosity, fraction ρo = Oil density, gm/cc ρg = Gas density, gm/cc μo = Oil viscosity, cP μg = Gas viscosity, cP

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E 0.80

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0.98

1.00

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0 200 400 600 800 1000 1200 1400 1600 1800 2000

Oil

Dens

ity, g

m/c

c

Oil

Gra

vity

, API

Bottomhole Elevation above Sea Level, ft

Frannie Tensleep: Oil Gravity and Density

Oil Gravity

Oil Density

E N H A N C E D O I L R E C O V E R Y I N S T I T U T E 0

0.1

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1

0 500 1,000 1,500 2,000 2,500 3,000 3,500

CO2 D

ensi

ty, g

m/c

c

Reservoir Pressure, psi

CO2 Density vs. Reservoir Pressure at 100 oF

Likely range of oil density at reservoir condition


Pressure Range for Miscible Gravity-Stable CO2 Injection

𝑷𝑴𝑴𝑷 < 𝑷𝑹𝑹𝑹 < 𝑷𝑴𝑴𝑴

PMMP: minimum miscibility pressure of CO2 PRES: average reservoir pressure during CO2 injection PMAX: a reservoir pressure at which CO2 becomes heavier than miscible oil


Simulation Analog of Gravity-Stable CO2 Injection

• Scaling parameters used in the 2D line-drive simulation models — Reservoir dip angle — Ratio of reservoir length to gross pay interval — Permeability aspect ratio (vertical/lateral) — Oil-water mobility ratio — Oil-CO2 mobility ratio — Buoyancy number — Injection and production pressures — Remaining oil saturation after water flood — Residual oil saturations to water and CO2


Estimated Oil Recovery by Gravity-Stable CO2 Injection

Scenarios of OOIP Calculation OWC at +450' Elevation after Tilting

OWC at +1107' Elevation before Tilting

Estimated OOIP 215.7 MMBO 245.5 MMBO Estimated Remaining-Oil-In-Place 96.6 MMBO 126.4 MMBO Oil Recovery after Water Flood 55.22% 48.51% Average Saturation of Remaining Oil 36% 41% Recoverable Oil By Gravity-Stable CO2 Flood 31.6 MMBO 49 MMBO Net CO2Usage for Incremental Oil Recovery 9.9 Mscf/BO 7.3 Mscf/BO

Additional Oil Recovery by Gravity-Stable CO2 Flood 14.6% of OOIP 20% of OOIP


9 Tensleep reservoirs in the Bighorn basin that have large TZ/ROZs have been identified as good candidates for miscible gravity-stable CO2 flood

Field Name Reservoir Name Basin Cum. Oil MMBO

Res. Depth ft Oil API

Initial Pressure psi

Res. Temp F Oil SG

Oil Density @Res. gm/cc

CO2 Density @Res. gm/cc

ρo - ρco2 gm/cc

BYRON EMBAR-TENSLEEP BIGHORN 122 5425 25.2 2085 130 0.903 0.890 0.641 0.249 ELK BASIN EMBAR-TENSLEEP BIGHORN 353 4490 30 2234 120 0.876 0.866 0.721 0.145 ELK BASIN SOUTH EMBAR-TENSLEEP BIGHORN 21 6846 28 2493 146? 0.887 0.871 0.625 0.246

FRANNIE PHOSPHORIA-TENSLEEP BIGHORN 135 2574 28.3 1350 96 0.885 0.879 0.609 0.270

GEBO EMBAR-TENSLEEP BIGHORN 17 4735 24.9 2223 145 0.905 0.889 0.561 0.328 MURPHY DOME TENSLEEP BIGHORN 39 4752 34 2150 117 0.855 0.846 0.705 0.141 GRASS CREEK EMBAR-TENSLEEP BIGHORN 47 4168 24.2 1300 110 0.909 0.901 0.368 0.533 SAGE CREEK TENSLEEP BIGHORN 5 3421 23.5 1400 96 0.913 0.907 0.641 0.266 BIG POLECAT TENSLEEP BIGHORN 7 5452 26.4 2050 118 0.896 0.886 0.689 0.197


Summary

• Based on Stone’s common-pool theory and an OWC at +1107’ elevation before tilting, the OOIP in the Frannie Tensleep is estimated to be 245.5 million barrels of oil.

• Due to restricted injection pressure of CO2, only “near-miscible” condition could be achieved at the structure top of the Frannie Tensleep.

• DST data and pressure buildup tests indicate a pressure communication among all Tensleep zones, assumably by vertical fractures.

• Because the Frannie Tensleep reservoir is relative shallow and CO2 is less dense than oil under the reservoir condition, gravity-stable CO2 flooding appears to be a superior method to CO2-WAG flooding.


Summary (cont’d)

• A preliminary study of simulation analog estimates that between 31.6 and 49 million barrels of oil could be recovered by gravity-stable CO2 flood depending on the remaining oil-in-place.

• Direct evidence shows that, at different locations of the structure, natural fractures are developed in a variety of orientations, laterally and vertically.

• Most of Tensleep wells at Frannie have been hydraulically fractured and, to some extent, are connected to natural fracture networks. However, well-to-well fracture conduits can change with time depending on at-the-time wellbore configurations and injection/production intervals.


Ongoing and Future Work

• Developing a dual porosity/permeability simulation model of the entire Tensleep structure at the Frannie field

• Simulating the effect of hydrodynamic flow and natural fractures on the titling of the Tensleep oil pool and its production/injection performance

• Evaluating various injector-producer configurations, e.g. CO2-WAG vs. gravity-stable CO2 injection, to identify the optimal option(s) for CO2 EOR in the main pay zone as well as in its TZ/ROZ


Acknowledgements

• We thank Merit Energy Company for supporting this study and providing the entire Frannie data set.

• The software donation of Petrel and Eclipse made by Schlumberger to EORI, which is being used in this study, is much acknowledged.


Thank You!

CO2-EOR Potential of Gravity -Stable CO Injection in … OIL RECOVERY INSTITUTE Shaochang Wo CO...

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