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.