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On Leakage and Seepage from Geologic Carbon Sequestration Sites

Unsaturated Zone Attenuation

Earth Sciences Division 90-1116, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720

View larger version (16K): [in a new window]   Fig. 1. Phase diagram for CO2 with approximate P, T path in the subsurface assuming hydrostatic pressure and geothermal gradient of 25°C km-1.

View larger version (28K): [in a new window]   Fig. 2. Density of CO2 as a function of pressure at three different temperatures.

View larger version (28K): [in a new window]   Fig. 3. Density as a function of concentration in the system CO2–air at P = 0.1 MPa.

View larger version (55K): [in a new window]   Fig. 4. Conceptual model and grid for the unsaturated zone model.

View larger version (54K): [in a new window]   Fig. 5. Shading indicates the mass fraction of CO2 in the gas phase, labeled contour lines indicate the water saturation, and vectors indicate the pore velocity of the gas phase for the base case at steady-state seepage rates with a leakage rate of (a) 4 x 104, (b) 4 x 105, and (c) 4 x 106 kg yr-1. The maximum vector size represents a value of approximately (a) 0.057, (b) 0.53, and (c) 3.6 m d-1.

View larger version (17K): [in a new window]   Fig. 6. Total flow rate of CO2 across the top boundary and maximum mole fraction of CO2 in the gas phase at the top of the system as a function of time after leakage enters the unsaturated zone.

View larger version (63K): [in a new window]   Fig. 7. Shading indicates the mass fraction of CO2 in the gas phase, labeled contour lines indicate the water saturation, and vectors indicate the pore velocity of the gas phase for a leakage rate of 4 x 105 kg yr-1 and at steady-state seepage rates with (a) a permeability of 1 x 10-9 m2, (b) an anisotropy of 1000:1, (c) a source radius of 10 m, and (d) a source radius of 1000 m. The maximum vector size represents a value of approximately (a) 1.0, (b) 8.4, (c) 17, and (d) 0.0048 m d-1.

View larger version (48K): [in a new window]   Fig. 8. The maximum seepage flux of CO2 and the maximum near-surface mole fraction of CO2 as a function of leakage rate at steady-state seepage conditions.

View larger version (28K): [in a new window]   Fig. 9. Barometric pressure used as top boundary condition.

View larger version (24K): [in a new window]   Fig. 10. Temporal evolution of (a) total surface flow of CO2 and (b) maximum near-surface mole fraction of CO2 for the base case with variable-pressure top boundary condition.

View larger version (68K): [in a new window]   Fig. 11. Shading indicates the mass fraction of CO2 in the gas phase and labeled contour lines indicate the water saturation for the case of zero leakage and an initial CO2 plume present in the unsaturated zone. (a) t = 6 mo, (b) t = 1 yr, (c) t = 5 yr, and (d) t = 10 yr. The maximum vector size represents a value of approximately (a) 2.8 x 10-2, (b) 2.0 x 10-2, (c) 7.5 x 10-3, and (d) 3.9 x 10-3 m d-1.