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CO2 Sequestration and Enhanced Oil Recovery Potential in Illinois Basin Petroleum Reservoirs

Beverly Seyler, Scott M. Frailey, Rex Knepp, Christopher P. Korose, Donald A. Keefer, and Damon A. Garner
Illinois State Geological Survey, Champaign, IL

Anticipating the need to store anthropogenic CO2, the Midwest Geologic Sequestration Consortium has studied the CO2 EOR potential of the Illinois Basin. To estimate the enhanced oil recovery from CO2 injection, general screening criteria developed from over 25 years CO2 EOR experience in West Texas was applied to Illinois Basin oil fields. These guidelines are based on ranges of API gravity, depth, oil composition, oil saturation, and viscosity. With the exception of the depth criteria, most Illinois oil reservoirs meet the general criteria for successful CO2 floods. The depth criterion is important because it determines the maximum injection pressure. These pressures were compared to a minimum miscibility pressure estimated from the pressure-temperature relationship of pure CO2. Each field in the Basin was classified as Miscible, Near-Miscible, or Immiscible based on the reservoir depth and pressure-temperature relationship of CO2.

CO2 EOR is frequently estimated using recovery factors which are the oil production as a fraction of the original oil in-place (OOIP). Consequently, the OOIP of each field is required. Therefore, a rigorous review of the OOIP of each field was undertaken. Decline curves were used to verify OOIP of some of the larger fields.

The CO2 oil recovery factor was quantified using Landmark's VIP compositional simulation program based on geologic models developed on the major producing intervals in the Basin. The geologic models built using deterministic and probabilistic approaches using Geographix software.

To find the final CO2 EOR targets for the Basin, a GIS analysis was used to combine the miscibility condition map, OOIP map, and recovery factor map.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005