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Sixth Annual Conference on Carbon Capture & Sequestration
Evaluation of Geological Formations
Dynamics of CO2 Plumes Encountering a Fault in a Reservoir
May 7-10, 2007 • Sheraton Station Square • Pittsburgh, Pennsylvania
Kyung Won Chang and Steven L. Bryant
The University of Texas at Austin
Acknowledgement
• Support is gratefully acknowledged from– CCP2 (CO2 Capture Project 2) – Geologic CO2 Storage Joint Industry
• Project Members of the JIP include– Chevron– Computer Modeling Group, Ltd.– ENI– ExxonMobil– Shell– TXU
Objective
• CCS technology aims at permanent storage– However, every storage site contains imperfections– Injected CO2 tends to rise toward the surface by
buoyancy
• Is it possible to improve the efficiency of CO2trapping?– Residual saturation trapping– Taking advantage of fault properties within the
reservoir• geometry • petrophysical properties
• Tilted reservoir– Dip angle is 5 degree
• Cartesian grid– 1 x 200 x 50– Cubic scale: 2ft x 2ft x 2ft
• No injection and production modeling
– Assign initial CO2 location to mimic an “inject low and let rise” strategy
– Perfectly closed boundary condition
Simulation Model Scheme: focus on interaction of buoyant plume with faults
Initial CO2
200ft
Reservoir Model Properties
• Domain assumed to have simple petrophysical properties – Homogeneous permeability, porosity– Several values of vertical to horizontal
permeability ratio (kv/kh): Anisotropy vs. Isotropy
– Compare behavior with and without residual saturation trapping
• Geometric Properties– Inclined fault– Declined fault– Cartesian grid blocks
• Petrophysical Properties– Sealing (low-permeable)
fault– Conductive (high-
permeable) fault– Transmissibility multiplier
Fault Modeling
Inclined
Declined
Description of Simulation Works
• Faults’ effects on the CO2 dynamics– Four typical cases
• Declined & Sealing• Inclined & Sealing• Declined & Conductive• Inclined & Conductive
– Anisotropic condition• kv/kh = 0.01
– Residual saturation trapping• Sgr = 0.2• Relative permeability curve
Relative Permeability Curve
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Gas Saturation, Sg
kr
krg (Drainage)
krw
krg (Imbibition)
Simulation Result: Declined & Sealing Fault
Top SealFault
50 years later 200 years later
1000 years later500 years later
Simulation Result: Declined & Conductive Fault
Top SealFault
100 years later 300 years later
500 years later 800 years later
Simulation Result: Inclined & Conductive Fault
Top SealFault
50 years later 200 years later
400 years later 800 years later
Simulation Result• CO2 trapping due to rock property
– Following example: Inclined & sealing fault• No residual gas saturation• Residual gas saturation
– Reservoir condition• Anisotropic condition (kv/kh=0.1)
300 years later 300 years later
The blue color means that the area is saturated with the residual gas saturation (Sgr = 0.2)
No residual gas saturation Residual gas saturation
Analysis of Plume Dynamics• Analysis of CO2 behavior
– Using flow vectors with gas saturation profiles– Example: Declined fault (Countercurrent flow)
Sealing fault : Gas flow Sealing fault : Water flow
Conductive fault : Water flowConductive fault : Gas flow
Conclusion• Interaction between fault geometry and fault’s
petrophysical property affects CO2 plume behavior– Barrier (another no-flow boundary of a domain)– Conduit (Leakage, “channeling effect”)
• Residual saturation trapping can be increased depending on fault’s properties– Conductive fault enlarges the area where CO2
invades• Permeability anisotropy makes more lateral CO2
migration– More benefits to CO2 capture
• Countercurrent flow of water (brine) phase makes benefits for CO2 trapping.
Thank you for your attention.
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