Transport modeling at multiple scales for the Illinois Basin-Decatur Project

The application of reactive-transport models is essential to understand and predict the impacts of carbon dioxide (CO₂) storage in deep saline reservoirs. This study was conducted to generate preliminary information in support of the Illinois Basin-Decatur Project (IBDP) using two modeling approaches: (i) flow and transport modeling of CO₂ at the basin scale, and (ii) geochemical modeling of CO₂ -saturated brine interactions with the primary seal at the IBDP. Using the TOUGH2-MP simulator, a flow and transport approach was developed to evaluate possible impacts of carbon sequestration at the basin scale. These modeling results should provide useful geologic and hydrogeologic data for future developers of carbon sequestration projects in the Illinois Basin and serve as a template for evaluating geologic carbon sequestration in other deep saline reservoirs. The modeling results demonstrated the significance of the geologic model for understanding the distribution of CO₂ and the predicted pressure changes with time. Geochemical modeling was applied to further understand potential interactions of CO₂ -saturated brine with the Eau Claire Shale. Geochemical simulations were conducted using TOUGHREACT, a numerical simulator that includes reactive chemistry, and Geochemist's Workbench®, which contains kinetic and reactive-transport modules. Simulations conducted for a 1000-year time frame yielded a decrease in porosity throughout the profile because of mineral precipitation. It was concluded that the rate by which ions diffuse into the caprock had little impact on changes in porosity when compared to the rates of mineral reaction.