SELECTION AND CHARACTERIZATION OF SITES FOR THE COMMERCIAL GEOLOGICAL SEQUESTRATION OF CO2 IN THE ILLINOIS BASIN

The Illinois Basin is host to numerous large sources of anthropogenic CO₂, and has been the focus of intense study as a region suitable for large-scale geologic sequestration of CO₂. Despite the potentially large total storage capacity of the lower Paleozoic sediments in the basin, sites capable of injecting and storing CO₂ at the rates typical of large coal-fired power plants require site-specific reservoir characteristics. We present a methodology to identify and rank potential sites in the Illinois Basin on the basis of their geologic and engineering characteristics, with particular focus on the importance of both vertical and lateral confinement of the plume of injected CO₂. The results show that only a small percentage of the basin is viable for early-stage commercial projects. The Loudon Anticline, located in Fayette and Effingham Counties in south-central Illinois, represents the best site for a regional CO₂ storage hub. The structure is a doubly-plunging anticline formed on the east-dipping western flank of the Illinois Basin, has about 200 feet of closure, and folds an 8000-foot-thick sequence of Paleozoic sediments. The primary storage horizon is the Cambrian Mt Simon Formation, a 1300-foot-thick fluvial to shallow-marine sandstone containing zones of high porosity and permeability. The Mt Simon is overlain by the Eau Clair Shale and carbonates of the Knox Group, which have sufficiently low permeability to confine injected CO₂ within the Mt Simon. The anticline’s four-way closure will restrict the lateral migration of injected CO₂ within a well-defined area, providing benefits in terms of acquiring subsurface storage rights and monitoring of the CO₂ during operations and post-closure. Reservoir flow simulations using porosity and permeability distributions from well logs and analog studies indicate that the Mt Simon has sufficient injectivity and capacity for up to ~500 Mt of CO₂, thereby demonstrating its suitability as a regional storage hub for nearby CO₂ sources. This storage capacity estimate may change based on further site characterization. The models also show that sites with complete lateral confinement will have predictable CO₂ plume footprints, whereas reasonable variations in reservoir properties dramatically change the footprint of sites with no such lateral constraints.