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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,

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Presentation on theme: "Potential impact of faults on CO 2 injection into saline aquifers & Geomechanical concerns of CO2 injection into depleted oil reservoirs Quentin Fisher,"— Presentation transcript:

1 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

2 Outline 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 CO 2 injection

3 Impact of faults on gas production (from van der Molen et al., 2003 EAGE conference on seals, Montpellier)

4 Fault 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)

5 Intrareservoir faults in the PermoTrias

6 Cataclastic faults

7 Cataclasites

8 Multi-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

9 Sorby multi-phase flow laboratory

10 Relative permeability results S w 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/cm 3 ) Research into practise within 6 months

11 Eclipse simulation of C0 2 injection into saline aquifer

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14 Geomechanics

15 Conditions for leakage along hydrofractures Pore pressure needs to overcome minimum horizontal stress while leakage occurs From Nordgård Bolås and Hermunrud, 2003

16 Stress path – P p /S h coupling If Mohr circle didnt change shape during overpressure development then shear fractures would always form Poroelastic effect means that S hmin increases with P p No P p /S h coupling P p /S h coupling

17 Stress path – P p /S h 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

18 Stress 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)

19 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 reservoirsConclusions

20 Future/on-going work

21 Stress arching Geomechanical methods for estimating leakage nearly always assume S v stays constant This ignores stress arching

22 4D-seismic and stress arching From Minkoff et al., (2004)

23 IPEGG – 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

24 Geomechanical/Seismic Coupling Benchmarks Thin Reservoir – Single Phase Flow Geometry Rectangular Reservoir 22,000ft x 11,000ft * 250 ft Quarter Symmetry Model Wellbore Output - Pressure

25 Geomechanical/Flow Coupling Thin Reservoir Example Contours of Subsidence after 4000 days Dynamic Relaxation/Transient Coupling Strategy Dean at al., 2003 Top of Reservoir Surface Fully Implicit Dynamic Relaxation/Transient ELFEN Fully Coupled

26 Elfen-Seismic elastic models Example P-wave velocities calculated using Elfen output based on Gassmans equation Elasticities


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