--> Abstract: Basin-Scale Hydrologic Impacts of CO2 Sequestration; Scaling Calculations Using Sharp Interface Theory, by M. Person, A. Banerjee, J. Rupp, P. Lichtner, M. Celia, C. Gable, and R. Pawar; #90084 (2008)

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Basin-Scale Hydrologic Impacts of CO2 Sequestration; Scaling Calculations Using Sharp Interface Theory

M. Person1, A. Banerjee1, J. Rupp2, P. Lichtner3, M. Celia4, C. Gable3, and R. Pawar3
1Indiana University, Bloomington, Indiana
2Indiana Geological Survey, Bloomington, Indiana
3Los Alamos National Labs, Los Alamos, New Mexico
4Princeton University, Princeton, New Jersey

The Illinois Basin hosts dozens of coal-fired power plants that produce millions of metric tons of CO2 annually. To assess the basin-scale hydrogeologic consequences of long-term (100-year), high-volume injection of supercritical CO2 into the Mount Simon Sandstone (Cambrian) of the Illinois Basin, injection was assessed using numerical modeling. We developed a basin-scale sharp-interface model that tracks the position of the CO2-brine-freshwater interfaces across most of Illinois and Indiana (about 200,000 km2). The sharp-interface system of equations was solved numerically using the finite element method. Within the model, pressurized brines were permitted to leak out of the Mount Simon into the overlying Eau Claire Formation (Cambrian) confining unit in an attempt to determine whether displaced brines would preferentially move laterally toward the basin margin or diffuse vertically. The pressure and CO2 lens thickness were calculated analytically and imposed as boundary conditions at injection nodes. Permeability and porosity were allowed to decrease with depth and position within the basin from about 125 to 10 mD and 20 to 5 percent, respectively. The thickness of the Eau Claire confining unit was also varied. CO2 was introduced at over 31 sites in close proximity to existing power plants in our model. We found that the gentle slope on the Mount Simon did not promote long-distance lateral migration of CO2. The relatively tight conditions at depth (greater than 2000 m) required using dozens of wells at individual power plant sites to avoid fluid pressures exceeding lithostatic levels near the wells. Pressure anomalies produced by injection extended out about 5 to10 km from injection sites before dissipating. A substantial superposition of pressure cones from adjacent injection wells was observed. Surprisingly, the position of the freshwater-saltwater interface did not move appreciably toward the margins of the basin. Future work will attempt to validate these findings using multi phase serial (FEHM) and parallel (PFLOTRAN) multiphase codes.

Presented AAPG Eastern Section Meeting, Pittsburgh, Pennsylvania 2008 © AAPG Eastern Section