Geologic Carbon Sequestration in the Illinois Basin: Numerical Modeling to Evaluate Potential Impacts

Circular 598, Geologic Carbon Sequestration in the Illinois Basin: Numerical Modeling to Evaluate Potential Impacts

Edward Mehnert, James R. Damico, Nathan P. Grigsby, Charles C. Monson, Christopher G. Patterson, and Fang Yang

The Illinois Basin in the north-central United States is a globally significant saline reservoir for geologic carbon sequestration. To evaluate the feasibility of future commercial-scale geologic carbon sequestration within the Illinois Basin, a basin-scale flow model was developed with TOUGH2-MP/ECO2N simulation software, run on National Science Foundation-funded supercomputers, and refined as new geologic data from the Illinois Basin – Decatur Project became available. Numerical modeling can be used to guide future efficient geologic carbon sequestration development in the region and understand its potential consequences. These geologic carbon sequestration models included the Mt. Simon Sandstone as the injection reservoir, the Eau Claire Formation (caprock), and the underlying pre-Mt. Simon and Argenta sandstones and Precambrian basement. For this project, we assessed the migration and fate of injected CO₂ and the pressure changes in this open reservoir in response to hypothetical future geologic carbon sequestration developments. Because of the uncertainty of the geologic and petrophysical data needed to build a geologic carbon sequestration model at the basin scale, a series of simulations were developed rather than a single best model. The resulting family of six solutions provided a range of possible simulations and should be useful for developing basin-scale geologic carbon sequestration in the Illinois Basin or other open basins. These six solutions included a 50-year injection period, but the overall simulation periods varied from 83 to 5,000 years.

Model results showed that a maximum of approximately 5 billion tonnes (5.5 billion tons, or 100 million tonnes [110 million tons] injected annually for 50 years) of CO₂ could be injected safely and permanently into the Illinois Basin. These results included reservoir pressures in the injection zone and overlying/underlying geologic strata and the phase distribution of CO₂ (free phase, residual saturation, and dissolved). Experts have predicted that a global CCS capacity of 92 billion tonnes (101 billion tons) will be needed to help stabilize atmospheric CO₂ concentrations. Thus, the Mt. Simon Formation in the Illinois Basin could be a globally significant CCS reservoir if developed efficiently.

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