ABSTRACT
Finite-element based sharp-interface models of CO2 injection were constructed for the Illinois Basin in which porosity and permeability were varied with depth from 0.2 to 0.05 and 125 to 5 mD, respectively within the Mount Simon Formation. We used 726 injection wells located near 41 power plants. The wells were spaced 2-4 km apart delivering 2.2 x 10⁵ m³ of CO2/year/well. After 100 years of continuous injection, deviatoric fluid pressures varied between 4.4 to 16.4 MPa across central and southern part of the Illinois Basin. Maximum deviatoric pressure reached about 46 % of lithostatic levels to the south. The pressure disturbance (> 0.03 MPa) propagated 9-13 km away from the injection wells resulting in significant well-well pressure interference. The CO2 plumes radial footprint was only 0.5-2 km after 100 years of injection. Net lateral brine displacement was insignificant due to leakage across the Eau Claire confining unit. If CO2 remains in a separate phase on geologic time scales, it would migrate northward at a rate of about 6m/1000 years. Because of historic and paleoseismic events in this region, care should be taken to avoid high pore pressures in the southern Illinois Basin.