ABSTRACT

This study simulated the injection of supercritical phase CO2 into the South Georgia Rift (SGR) basin to evaluate the feasibility of long-term storage. Because of the lack of basin data, an equilibrium model was used to estimate the initial hydrostatic pressure, temperature, and salinity gradients that represent our study area. For the equilibrium model, the USGS SEAWAT program was used and for the CO2 injection simulation, TOUGH2-ECO2N was used. A stochastic approach was used to populate the permeability in the injection layer within the model domain. The statistical method to address permeability uncertainty and heterogeneity was sequential Gaussian simulation. The target injection depths are well below the 1 km (∼0.62 mi) depth required to maintain CO2 as a supercritical fluid. There were very little data pertaining to the properties in the deep Jurassic/Triassic (J/Tr) SGR basin formations. So, conservative porosity and permeability starting points were postulated using data from analogous basins. This study simulated 30 million tons of CO2 injected at a rate of 1 million tons per year for 30 yr, which is the minimum capacity requirement by the U.S. Department of Energy (DOE) for a viable CO2 storage reservoir. In addition to this requirement, a 970-yr shut-in time (no injection) was also simulated to better determine the long-term fate and migration of the injected CO2 and to ensure that the SGR basin could effectively contain 30 million tons of CO2. The preliminary modeling of CO2 injection indicated that the SGR basin is suitable for geologic storage of this U.S. DOE stated minimum capacity.

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