Task 4: Damage & StimulationTechnical Status May-June 2000
TerraTek, Inc.
Heriot -Watt University
Triangle Engineering
Duke Engineering and Services, Inc.
eFirst Technologies
Gas Research Institute
Advantek, International, Inc
VIPS
Task 4: Status
4.1 Acquisition of Field Data4.1 Acquisition of Field Data
4.2 Quantitative Evaluation4.2 Quantitative Evaluation
4.3 Well Testing Techniques4.3 Well Testing Techniques
4.4 Damage effects and damaging agents
4.4 Damage effects and damaging agents
‘D.P. Format’ (Mar ‘99) on ‘Data CD’ Data list (review 5 soon)
‘Data CD’ (May 00) Technical presentations (‘99-‘00) Stimulation Record listing
Duke working on fall-off review SRT multi-rate spreadsheet (being/
tested reviewed by TT) (Apr ‘00)
(Matrix) Damage Report (May ‘00) Technical presentations (‘99-‘00) Surface systems overview (In
progress)
Pro
ject
Su
bta
sks
Task 4: Status (cont...)
4.5 Review of Mitigation /Stimulation Techniques
4.5 Review of Mitigation /Stimulation Techniques
4.6 Economics of Damage vs.Damage Mitigation vs. Stimulation
4.6 Economics of Damage vs.Damage Mitigation vs. Stimulation
4.7 Guidelines for best practices
4.7 Guidelines for best practices
Stimulation techniques overview (sent to TT mid May)
Problem-solution spreadsheet
Presentation in Stavanger (Feb.’00) Discussed in this workshop
To be derived from proposed Analysis Strategy
Pro
ject
Su
bta
sks
A. Stimulation Philosophy
B. Stimulation Techniques
– Chemical (Acidising) and Mechanical (Fracturing)
– Field Cases
C. Analysis Strategy
Task 4: Presentation Overview
Stimulation Philosophy
Chemical (acidising)•need to know:
– source of damage &– location of damage
–Input from Task 2
• Choice of stimulation fluid– Remove damage (not always acid)– no deleterious effects on formation
Mechanical (Hydraulic Fracturing)– Bypass damage with high permeability fracture
Injection Damage Mechanisms (1)
• Particle Plugging– Solids and oil in the water (also emulsions?)
• Water / Formation Incompatibilities– Fines Migration and Clay Swelling
• Hydrocarbon Effects– Wax / asphaltines deposits & relative permeability
effects
• Scale– Calcium carbonate, calcium sulphate, barium sulphate
etc.
• Corrosion– Generates iron particles (plugging)– Alters tubing friction - increased tubing roughness (&
diameter?)
Injection Damage Mechanisms (2)
• (lack of) Bacterial Control– Biomass and / or “Schmoo”
– Described by Fambrough et al. (SPE 28976), McLelland and others
• Main components of “Schmoo”:– Sand and formation fines in the PW– Hydrocarbon material in the PW (OIW)– Iron sulphide, from the injection system– Production chemicals– Biomass-material
• “Schmoo” prediction requires extensive water quality / surface facility information
PWRI Damage Mechanisms
Damaged zone (mud filtrate,
completion/injectionfluids, etc)
Fines migrati
on
Mud filter cake
Corrosion
Iron solids
plugging
Fractures plugged
with solids from
injection fluid
Organic scalingBacteria growth, plugging, “schmoo”
Inorganic
scaling
Formation pore
plugging•Solid
particlesOil dropletsOily solid particles
Relativepermeabili
tychanges
Formation Damage - Hydrocarbon deposition
R1
R2
Oil droplet larger than pore
throat
Dissolved Oil
Wax Depositio
n
Free Oil
Asphaltene
Deposition ? Emulsifie
d Oil
Schmoo
Stimulation Philosophy
Chemical (acidising)•need to know:
– source of damage &– location of damage
–Input from Task 2
• Choice of stimulation fluid– Remove damage (not always acid)–additives– no deleterious effects on formation
Mechanical (Hydraulic Fracturing)– Bypass damage with high permeability fracture
Maersk - “Field A” water injection system
Stimulation fluid chosen on basis of damage
• Injection system fouling reported (Check-valve pictured)• Deposits mainly Oil and Iron Sulphide• System Cleaned with an acid / surfactant solution
Impairment
Cement (carbonate)
Quartz
Native rock
Pore lining clay
Pore filling clay
Remaining pore space
ACID (HCL/HF)
Secondary reaction products
Thermodynamic equilibrium simulation chose optimum acid formulation, depending on rock/damage mineralogy
- Increased porosity and permeability - Damage removed
Acidising - Acid formulations
Many acid formulations used for matrix acidising:•Hydrochloric Acid (HCl)•Mud Acids•Organic Acids
•Does not removeall damage typese.g. silica
Mud Acid
The damaged well
K
Kd
rd rw
Damaged Zone rd Damaged zone radius
k Virgin rock permeability kd Damaged zone permeability k > kd kacid
Fully acidised zone, all solubleminerals dissolved
kprecip Partically acidised zone with
precipitated acid /rock reactionproducts
kprecip < k > kacid
1. The damaged well
k kd
k
k kd
2. A small acid treatment
3. A large acid treatment
kacid
rd
kacid
kprecip
kprecip
rd
rd
The mud acidising
process
Stimulation of Carbonate Formations
•(Matrix HCl) Acidising of Carbonate formations is different from treatment of sandstones.
•Wormhole formation & (surface) Acid Wash
a) Cased hole
b) Open hole
Potential Damage caused by Stimulation Fluids
• Deconsolidation of the rock matrix
• Fines generation => acid only partly dissolves formation minerals present between the grains.
• Secondary precipitation => blockage of the pores and pore throats (impairment).
• Fluid incompatibilities.
• Acid precipitation of an insoluble sludge
• Surfactants =>
create a (highly) viscous emulsion
• Relative permeability / wettability changes => due to Surfactants
Repetitive Stimulation - Why?
•Options: continuing damage or acid selection
ELF PICTURE
ELF-3 W-1
0.00E+00
2.00E+05
4.00E+05
6.00E+05
8.00E+05
1.00E+06
1.20E+06
1.40E+06
1.60E+06
1.80E+06
0 2,500,000 5,000,000 7,500,000 10,000,000 12,500,000
Cummulative Injection Volume (BBL)
Pre
ssu
re T
erm
(p
si*d
ays)
0
2,500
5,000
7,500
10,000
12,500
15,000
17,500
20,000
22,500
BH
P (p
si)
& I
njec
tion
Rat
e (B
PD
)
HallInj. Pressure "BHP"Injection RatePWAcidification Jun/95Acidification Sep/95Acidification Nov/95Acidification May/96Acidification Oct/96Acidification Nov/96Acidification Aug/97Acidification Dec/98Acidification Apr/99Acidification May/99Acidification Jun/99Acidification Jul/99Acidification Aug/99Acidification Sep/99Acidification Oct/99Acidification Oct/99Acidification Nov/99Acidification Jan/00Acidification Jan/00
HALL PLOT
Acid treatments
Selection of Acid Composition
Repetitive Acidising of Sandstones
•Often shows decreasing success
•Damage Location - Placement techniques
•Stimulation fluid selection
Field Case - Chevron
Repetitive Stimulation in Carbonate Field
Decline Rate decreases after each stimulation
Mechanical Stimulation
No need to identify formation damage type & location
(Careful) choice of frac. chemicals avoids formation damage (also Acid Fracturing)
formation deconsonsolidation not an issue
PW Injection may plug Proppant pack
proppant pack perm >10X that of formation
Damage location controlled by size PW particles (Frac. mouth area limited)
Frac Pac increases “filter area”
This form of damage avoided by Hydraulically Induced Fracturing (no proppant)
Also Specialist applications e.g. initiation of TIF process
Analysis of producedand formation water
characteristics
Formation damagemechanisms
Remedial action
TSS: particle count (ppm)and size distribution (mm)
Formation / pore pluggingcreating filter cakes
•Solid particles•Oil droplets
•Oily solid particles
Emulsions, wax, oil bank(affecting relative perm.)
Other hydrocarbon deposits(schmoo) etc.
Acid stimulationFracture (increase wellbore)
Clean water
Control
Filtration
OIW: Particle count (ppm)and droplet size (mm)
Solvents and/or surfactantsinjection
Separation, solvents,surfactants
Dissolved gases (CO2, O2,H2S etc.)
Corrosion (tubing, surface equipment damages,
causing iron solids plugging)
Bacterial count (CFU/g) Bacterial growth, pluggingCorrosion due to SRB
TDS (ppm)AW / PW compatibility
Temperature
Scale precipitation:CaCO3, CaSO4, BaSO4 etc.
Critical injection velocity(m/s)
Fines migration
Acid stimulation
Biocides
Tubing wash or matrix stimulationFluid depends on scale type
Acid stimulationFracturing
Clean Water
Corrosion inhibitors (Scavengers)
Material selection
Biocides
Scale inhibitorinjection at surface
Adjust flow rate (bpd),Increase pay zone
periodic stabling treatments
Damage - Mitigation - Stimulation “Roadmap”
PWRI Damage Mechanisms
Damaged zone (mud filtrate,
completion/injection fluids, etc)
Fines migrati
on
Mud filter cake
Corrosion
Iron solids
plugging
Fractures plugged
with solids from
injection fluid
Organic scalingBacteria growth, plugging, “schmoo”
Inorganic
scaling
Formation pore
plugging•Solid
particlesOil dropletsOily solid particles
Relativepermeabili
tychanges
PWRI Stimulation Techniques
SurfactantsSurfactants
Solvents /Mutual solvents
Solvents /Mutual solvents
SequesteringAgents
SequesteringAgents
CorrosionInhibitorsCorrosionInhibitors
OrganicAcids
OrganicAcids
Mud AcidMud Acid
HydrochloricAcid (HCl)
HydrochloricAcid (HCl)
Clean water flush(e.g. sea water
injection)
Clean water flush(e.g. sea water
injection)
Frac-PackFrac-Pack
Closed FractureAcidising
(CFA)
Closed FractureAcidising
(CFA)
ThermallyInduced
Fracturing(TIF)
ThermallyInduced
Fracturing(TIF)
Acid-FracAcid-Frac
ProppedHydraulicFracturing
ProppedHydraulicFracturing
Back-flowto clean
perforations
Back-flowto clean
perforations
Stim-gunStim-gun
WaterHammer
Stimulation
WaterHammer
Stimulation
Acidising Other MethodsAdditives Fracturing
HydraulicFracturingHydraulicFracturing
Field data
• Stimulation Data on CD:• ELF- 3• NAM-1• Maersk A-25 & B-03• BP Amoco Prudhoe Bay H-09• PanCanadian Countess
• Experience from 6 companies to be presented by today’s speakers
Field Case - ELF-3 W1
ELF-3 W-1
0.00E+00
2.00E+05
4.00E+05
6.00E+05
8.00E+05
1.00E+06
1.20E+06
1.40E+06
1.60E+06
1.80E+06
0 2,500,000 5,000,000 7,500,000 10,000,000 12,500,000
Cummulative Injection Volume (BBL)
Pre
ssur
e Te
rm (p
si*d
ays)
0
2,500
5,000
7,500
10,000
12,500
15,000
17,500
20,000
22,500
BH
P (p
si)
&
Inje
ctio
n R
ate
(BP
D)
HallInj. Pressure "BHP"Injection RatePWAcidification Jun/95Acidification Sep/95Acidification Nov/95Acidification May/96Acidification Oct/96Acidification Nov/96Acidification Aug/97Acidification Dec/98Acidification Apr/99Acidification May/99Acidification Jun/99Acidification Jul/99Acidification Aug/99Acidification Sep/99Acidification Oct/99Acidification Oct/99Acidification Nov/99Acidification Jan/00Acidification Jan/00
HALL PLOT
Acid treatments
Field Case - ELF-3 W2
ELF3 W-2
0.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
Dec
-95
Feb-
96
Apr
-96
Jun-
96
Aug
-96
Oct
-96
Dec
-96
Feb-
97
Apr
-97
Jun-
97
Aug
-97
Oct
-97
Dec
-97
Feb-
98
Apr
-98
Jun-
98
Aug
-98
Oct
-98
Dec
-98
Feb-
99
Apr
-99
Jun-
99
Aug
-99
Oct
-99
Dec
-99
Feb-
00
Apr
-00
Date
Inje
ctiv
ity I
ndex
(BPD
/psi
)
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
Bot
tom
hole
Inj
ectio
n Pr
essu
re (p
si)
Inj. Index "II"Inj. Pressure "BHP"PWAcidification Jun/96Acidification Jun/96Acidification Oct/96Acidification Dec/96Acidification Jan/97Acidification Feb/97Acidification Mar/97Acidification Aug/97
Injectivity Index and Pressure vs. Time
Acid treatments
Analysis Strategy (1)
• Review data made available to PWRI project– Developed familiarity with contents– Data profiling to help identify where it is most
relevant– (Very) Basic quality control checks
• Define stimulation success (economics)• For discussion in this workshop
• Two types of analysis possible:– statistical analysis on large data sets– specific example well analysis
• Guidelines & Best Practices
Process of Data cataloguing started
Stimulation Data on CD:
• ELF- 3
• NAM-1
• Maersk A-25 & B-03
• BP Amoco Prudhoe Bay H-09
• PanCanadian Countess
Statistical Analysis
• Countess data set potentially had opportunity for large scale analysis similar to Prudhoe Bay (PEA 23)– 22 wells with stimulation history
• 15 mud acid, 10 HCl acid, 4 propped hydraulic frac
• Visit to Pan Canadian:– Similar stimulations in different wells had
inconsistent performance i.e. treatment successs / failure
erratic– Advised Wellfile data may be inaccurate / or
incomplete
Damage & Stimulation Overview Spreadsheet
Work in progress
C-06-07-018-15
0.00E+00
1.00E+06
2.00E+06
3.00E+06
4.00E+06
5.00E+06
6.00E+06
7.00E+06
8.00E+06
9.00E+06
1.00E+07
1.10E+07
0 2,500,000 5,000,000 7,500,000 10,000,000 12,500,000 15,000,000 17,500,000
Cummulative Injection Volume (BBL)
Pres
sure
Ter
m (p
si*d
ays)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
10.0
11.0
Inje
ctiv
ity I
ndex
(BPD
/psi
)
HallInjec. IndexPWPWAcid Squeeze May/76stimulation ?Jet, Re-perf May/96
HALL PLOT
Acid squeeze, Re-Perf.
31-May-76
Jet, Re-Perf. 17-May-96
stimulation treatment ?
Treatment Analysis Template
Formation
Sandstone Carbonate
Hard Soft Hard Soft
Injection regime
Matrix (task 2) Fracture Naturally fractured
Work in progress
Action Plan•List & profile project stimulation data
•Identify gap’s between well categories & project data
•Identify any areas where data is “missing” &
•Propose data sets for “hi-grading”
• produce “stimulation CD” {July}
•Analyse data
•Complete evaluation of collected Published literature:
PWRI: mainly Prudhoe Bay & Carbonate formations Sea Water: all types
•Generation of best practices by linking donated data, reports, published literature etc.
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