Integrated modeling of basin-scale impacts on groundwater resources and plume-scale transport behavior of geologic carbon sequestration in the illinois sedimentary basin

A basin-scale multiphase flow model was developed to assess the impact of geologic carbon sequestration (GCS) in the deep saline, Illinois Basin on groundwater resources in northern Illinois. The model covered the Mt. Simon Sandstone as storage formation and the overlying Eau Claire aquitard as caprock. A hypothetical scenario, with 20 storage sites in a most suitable core injection area and an annual rate of five million tonnes of CO(2) for injection over 50 years at each site, was employed. The integrated modeling of basin-scale groundwater flow and of two-phase CO(2)-brine flow within CO(2) plumes was conducted using the parallel TOUGH2/ECO2N simulator and a 3D unstructured mesh of 1.25 million gridblocks with local refinement. Simulation results indicate various favorable conditions for safe storage of large volumes of CO(2) in Mt. Simon, including a deep high-permeability and high-porosity arkosic unit used for CO(2) injection, and secondary seals in Mt. Simon for significant retardation of upward CO(2) migration. The simulated CO(2) plume behavior is supported by observations in natural gas storage fields in the basin, as an analog to GCS. The simulation results also indicate that (1)significant pressure buildup (similar to 35 bar) in the core injection area is produced, but still ensuring caprock geomechanical integrity, (2) moderate pressure buildup (as high as 1 bar) occurs in northern Illinois and might have an impact on brine intrusion into shallow freshwater aquifers, and (3)no direct impact of brine migration within the updip storage formation in northern Illinois. In comparison, the basin-scale environmental impact of GCS is less significant than that of the long-term intensive groundwater extraction from overlying freshwater aquifers in the metro-Chicago region.