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Potential impact of faults on CO 2 injection into saline aquifers & Geomechanical concerns of CO2 injection into depleted oil reservoirs. Quentin Fisher, Sergey Skachkov Suleiman Al-Hinai, Carlos Grattoni. School of Earth and Environment, University of Leeds E-mail: [email protected]. - PowerPoint PPT Presentation
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Potential impact of faults on COPotential impact of faults on CO22 injection into saline aquifersinjection into saline aquifers
&&Geomechanical concerns of CO2 Geomechanical concerns of CO2
injection into depleted oil reservoirsinjection into depleted oil reservoirsQuentin Fisher, Sergey SkachkovSuleiman Al-Hinai, Carlos Grattoni
School of Earth and Environment, University of LeedsE-mail: [email protected]
OutlineOutline • Faults and fluid flow
• Relative permeability of fault rocks
• Simulations of CO2 injection into faulted saline aquifer
• Stress path in re-inflated reservoirs
• Ongoing/future research into geomechanicals of CO2 injection
Impact of faults on gas productionImpact of faults on gas production
(from van der Molen et al., 2003EAGE conference on seals, Montpellier)
Fault Seal Types in SiliciclasticsFault Seal Types in Siliciclastics
Juxtaposition seal(by far the most common type of barrier to production in heterolithic reservoirs)
Fault rock seal(fault seal sensu stricto – important for Rotliegend)
Intrareservoir faults in the PermoTrias
Cataclastic faultsCataclastic faults
CataclasitesCataclasites
1500
2000
2500
3000
3500
4000
4500
0.00001 0.0001 0.001 0.01 0.1 1 10
Fault permeability (mD)M
axim
um b
uria
l dep
th (m
)
Multi-phase flow properties of faultsMulti-phase flow properties of faults
• Above gas water contact two phases may be present in the pore space
• This lowers the permeability to both gas and water
Sorby multi-phase flow laboratorySorby multi-phase flow laboratory
Relative permeability resultsRelative permeability results
• Sw altered using centrifuge and humidity chambers
• Relative permeability of faults as a function of height above FWL (assuming petroleum and brine densities of 0.5 and 1 g/cm3)
• Research into practise within 6 months
01000200030004000500060007000
0.001 0.01 0.1 1
krg
Hei
ght a
bove
FW
L (ft
)
0200400600800
100012001400
0.001 0.01 0.1 1
Krg
gas-
wat
er P
c (p
si)
Eclipse simulation of C0Eclipse simulation of C022 injection injection into saline aquiferinto saline aquifer
Eclipse simulation of C0Eclipse simulation of C022 injection injection into saline aquiferinto saline aquifer
Eclipse simulation of C0Eclipse simulation of C022 injection injection into saline aquiferinto saline aquifer
GeomechanicsGeomechanics
Conditions for leakage along Conditions for leakage along hydrofractureshydrofractures
• Pore pressure needs to overcome minimum horizontal stress while leakage occurs
From Nordgård Bolås and Hermunrud, 2003
Stress path – PStress path – Ppp/S/Shh coupling coupling
• If Mohr circle didn’t change shape during overpressure development then shear fractures would always form
• Poroelastic effect means that Shmin increases with Pp
No Pp/Sh coupling
Pp/Sh coupling
Pp/Sh coupling
Stress path – PStress path – Ppp/S/Shh coupling coupling
• Knowledge of stress path is needed to predict likelihood and type of failure during both depletion and inflation
• From Hettma et al., (1998) – SPE 63261
Stress path during re-inflationStress path during re-inflation
• Estimates of stress path have been made from repeated leak-off tests during depletion
• Some evidence shows that stress paths are lower during inflation than deflation (i.e. fracture pressure is lower) From Santarelli et al., (SPE, 47350)
• Intrareservoir faults could cause significant barriers to CO2 injection into saline aquifers but are less likely to affect the movement of the brine
• Fracture gradient may be lower than virgin pressure when re-injecting CO2 into depleted reservoirs
• Project up and running to further investigate geomechanics of reservoirs and to predict seismic properties in stress sensitive reservoirs
ConclusionsConclusions
Future/on-going workFuture/on-going work
Stress archingStress arching
• Geomechanical methods for estimating leakage nearly always assume Sv stays constant
• This ignores stress arching
R eservo ir
su rface
com p action
S tre tch ing andreduction in v v
Increase in
In cresed shea rs tress
C asingsub ject toshear
4D-seismic and stress arching4D-seismic and stress arching
From Minkoff et al., (2004)
IPEGG – Technological PositionIPEGG – Technological Position
Calculate seismic
attributes
Create coupled stress – flow
software
Groundtruth with field data
Use to forward model for predictions
• 3D• Built based on
simulation grid• User friendly• Large range of
constitutive models• Local grid capabilities
to allow modelling of well bore stability
• 4D response• Anisotropy• Microseismicity
c
• JIP between Leeds, Bristol and Rockfield Software Ltd
• Sponsored by BP, BG, ENI and Statoil
Geomechanical/Seismic CouplingGeomechanical/Seismic Coupling Benchmarks Benchmarks
Thin Reservoir – Single Phase Flow
Geometry• Rectangular Reservoir
22,000ft x 11,000ft * 250 ft• Quarter Symmetry Model
Wellbore
Output - PressureOutput - Pressure
Geomechanical/Flow CouplingGeomechanical/Flow CouplingThin Reservoir ExampleThin Reservoir Example
Contours of Subsidence after 4000 daysDynamic Relaxation/Transient Coupling Strategy
Dean at al., 2003
0
1
2
3
4
5
6
7
8
0 500 1000 1500 2000 2500 3000 3500 4000Time (Days)
Subs
iden
ce (f
t) Top of Reservoir
Surface
Fully Implicit Dynamic Relaxation/Transient
ELFEN Fully Coupled
Elfen-Seismic elastic modelsElfen-Seismic elastic models
2525
3185
Example P-wave velocities calculated using Elfen output based on Gassman’s equation
Elasticities