GEOCHEMICAL MODELING OF CARBON SEQUESTRATION IN THE MT. SIMON SANDSTONE

The Midwest Geologic Sequestration Consortium lead by the Illinois State Geological Survey plans to inject 1 million tonnes of carbon dioxide into the Mt. Simon formation over three years. The Illinois Basin Project-Decatur Site will be the first demonstration of carbon sequestration in a deep saline reservoir in the Illinois Basin. In preparation for this injection, we have constructed preliminary geochemical models to predict geochemical changes in the brine and reservoir rock following injection and to provide a basis for building more complicated models as more site-specific data become available. Previous computer simulations of carbon sequestration in the Mt. Simon used chemical and mineralogical data obtained from a nearby natural gas storage field. We have extended these preliminary models to the greater pressures and temperatures expected at the Illinois Basin Project Decatur site. These models are the first step towards creating larger reactive transport models for the injection zone. TOUGHREACT and React were used to allow us to compare the results of the two codes. We plan to model four scenarios for this injection site: CO2 saturated brine interacting with 1) an arkosic sandstone, 2) a quartz rich sandstone, 3) a fine-grained interbed material, and 4) the Eau Claire caprock. For each of these scenarios, the models will predict changes in porosity and therefore possible changes in formation permeability. Previous results revealed that the incorporation of mineral kinetics led to large changes in the predicted mineralogy upon CO2 interaction with reservoir minerals; thus, we studied the effects of solution/dissolution kinetics at the Decatur site.