POTENTIAL FOR GEOLOGIC SEQUESTRATION OF CO2 IN ILLINOIS

Illinois is participating in a five state consortium on CO2 sequestering with Kansas, Indiana, Ohio, and Kentucky to produce the Midcontinent Interactive Digital Carbon Atlas and Relational Database. The purpose of the project is to identify sources of CO2 (such as power plants) and potential sinks in geologic settings in the five state region. Coal seams, saline aquifers and petroleum reservoirs generally comprise the geologic sinks in Illinois. Coal availability maps have been completed for the major coal seams in Illinois that are potential sinks for CO2. By analyzing coal thickness, depth, mined areas, and proximity of select deposits to sources of CO2, this study will focus on resources that are likely to be mined in the future and identify areas that may be favorable for coal-seam CO2 sequestration. Regional structure mapping of one of the stratigraphically oldest sequestration targets, the Mt Simon Sandstone (Cambrian) suggests that this saline aquifer has potential for sequestration of large volumes of CO2. Petroleum reservoirs offer many additional opportunities for sequestering CO2 and, at the same time, provide a proven method of improving and enhancing recovery from oil reservoirs. Miscible CO2 flooding of reservoirs would be confined to the deepest portions of the Illinois Basin, where reservoirs are located deeper than 2,400 feet (subsea). While immiscible CO2 flooding is not as effective in petroleum recovery as miscible flooding, it may be an additional technique with widespread potential in Illinois, given the numerous shallow, partially-depleted petroleum reservoirs in sandstones and the proximity of CO2 sources. Most petroleum reservoirs in Illinois are shallower than the 2,400 foot depth generally considered effective for miscible flooding. The Cypress Sandstone (Mississippian), a widely-distributed, prolific oil reservoir, has been identified as a major target for injection of CO2 as a tertiary recovery mechanism in depleted and partially-depleted petroleum reservoirs in the Illinois Basin. Maps of net sandstone thickness for the Cypress will be used to estimate potential volumes for CO2 injection. Other strata that are potential sinks are reservoirs in Pennsylvanian sandstones and other Mississippian sandstones.