Carbon Capture and Storage and Precambrian Topography in the Illinois Basin

Hannes E. Leetaru and Robert Finley
Illinois State Geological Survey, Champaign, IL, [email protected], [email protected]

The Cambrian Mt. Simon Sandstone is the most important carbon sink available for the sequestration of CO2 in the heavily industrialized Midwest of the United States. In the Illinois Basin, the lower Mt. Simon Sandstone is interpreted to have been deposited in a Precambrian rift basin that formed during the breakup of the supercontinent Rodinia. This rifting event provided accommodation space for the deposition of over 2,600 feet (792 meters) of Mt. Simon siliciclastic sediments. Areas outside the proposed rift basin have a significantly thinner Mt. Simon section. The characterization and operation of a Carbon Capture and Storage (CCS) site in the Illinois Basin can be improved by understanding the effect Precambrian basement topography has had on Mt. Simon Sandstone deposition.

The Illinois Basin – Decatur Project (IBDP) is a one million tonne CCS demonstration project located in Macon County, Illinois. Led by the Midwest Geological Sequestration Consortium, one of seven US Department of Energy – National Energy Technology Laboratory funded Regional Sequestration Partnerships; IBDP began injection of CO2 into the Mt. Simon Sandstone in November 2011. Geologic modeling is being used to better understand CO2 plume migration as a function of Precambrian basement impact. Three-dimensional seismic reflection data from IBDP suggests as much as 200 feet (61 meters) of Precambrian topographic relief is present in the study area. The Mt. Simon Sandstone appears to thin over topographic high areas and thicken in the valleys. IBDP encountered the best reservoir quality rocks in alluvial fan and braided river deposits of the lower Mt. Simon with average porosities of 22% and permeabilities of 200 mD, respectively. Regional mapping suggests that these lower Mt. Simon reservoirs are prevalent within the rift basin. Both seismic reflection data and well control data suggest that the braided river deposits formed significant lateral and vertical reservoir heterogeneity that may impact the prediction of plume migration.

AAPG Search and Discovery Article #90154©2012 AAPG Eastern Section Meeting, Cleveland, Ohio, 22-26 September 2012