The use of crude oil-bearing strata as geological sinks for sequestration of carbon dioxide (CO₂) includes a value-added component for recovering new oil from existing oil fields that have undergone primary and/or waterflood production. Carbon dioxide has been used in enhanced oil recovery (EOR) for more than two decades in the Permian Basin of west Texas. This CO₂ experience suggests that following water flooding with CO₂ flooding produces an additional 10% of original oil in place (OOIP) or an additional 25% beyond total oil produced during the primary and water flooding phases.

The Midwest Geological Sequestration Consortium has studied the CO₂ EOR potential of the Illinois Basin in Illinois, Indiana, and Kentucky. Oil has been produced from this basin for more than a century, to date yielding a cumulative production of 4.3 billion of an estimated 14.1 billion bbl of OOIP. The consortium’s study focuses on three topics regarding the potential of CO₂ flooding in Illinois Basin fields. The first is evaluation of oil recovery potential employing geological, geostatistical, and reservoir models built for specific geological settings. The second is estimation of total hydrocarbon available to CO₂ flooding, requiring an updated estimate of the basinwide OOIP. The third is calculation of the total volume of carbon that could be sequestered by such programs and the volume of additional hydrocarbon recovery that might reasonably be expected.

Using west Texas experience as a guideline, reservoir modeling results suggest that 0.86–1.3 billion bbl of oil may be recoverable from the Illinois Basin using CO₂ EOR. Along with this incremental oil recovery, an estimated 154,000–485,000 tons of CO₂ can be sequestered simultaneously.