Basin-scale environmental impact of geologic carbon sequestration (GCS): Evaluation of a hypothetical scenario for full-scale deployment in the Illinois Basin

• An integrated model was developed to represent a hypothetical fullscale deployment scenario of carbon sequestration in the Illinois Basin • Simulated plume-scale behavior indicates favorable conditions for CO ₂ storage in Mt Simon: • High-K and high-θ Arkosic Unit provides Excellent CO₂ Injectivity in lower Mt Simon, • Alternating layering Significantly Retards upward CO₂ migration, • Thick, extensive Mt Simon provides Large CO₂ Storage Capacity, and • Thick regional-scale Eau Claire seal ensures Long-Term CO ₂ Containment in the storage formation. • Simulated basin-scale behavior indicates that • High hydraulic diffusivity helps reduce pressure buildup in the core injection area, thus enhancing caprock geomechanical integrity, • High regional caprock permeability allows for natural attenuation of pressure in the storage formation, thus enhancing storage capacity of Mt Simon, • Brine upward migration occurs in the core injection area, into a thick series of overlying saline aquifers and aquitards, at a maximum velocity of ∼8 mm/year • Environmental Impact on Groundwater Resources • Environmental concerns of brine migration into the updip Mt Simon in northern Illinois and southern Wisconsin may not be an issue, • Moderate pressure buildup is obtained in northern Illinois, where upward brine migration might be a concern, if local seal imperfections exists, • Impact of GCS on shallow freshwater resources in northern Illinois may be less than that induced by heavy pumping from overlying freshwater aquifers. • Further research is needed to couple a regional groundwater flow model with the integrated model for environmental impact assessment.