CO{sub 2} Injectivity, Storage Capacity, Plume Size, and Reservoir and Seal Integrity of the Ordovician St. Peter Sandstone and the Cambrian Potosi Formation in the Illnois Basin Page: 3 of 29

                                
ABSTRACT
The Cambro-Ordovician strata of the Illinois and Michigan Basins underlie most of the states
of Illinois, Indiana, Kentucky, and Michigan. This interval also extends through much of the
Midwest of the United States and, for some areas, may be the only available target for
geological sequestration of CO2. We evaluated the Cambro-Ordovician strata above the
basal Mt. Simon Sandstone reservoir for sequestration potential. The two targets were the
Cambrian carbonate intervals in the Knox and the Ordovician St. Peter Sandstone.
The evaluation of these two formations was accomplished using wireline data, core data,
pressure data, and seismic data from the USDOE-funded Illinois Basin - Decatur Project
being conducted by the Midwest Geological Sequestration Consortium in Macon County,
Illinois. Interpretations were completed using log analysis software, a reservoir flow
simulator, and a finite element solver that determines rock stress and strain changes resulting
from the pressure increase associated with CO2 injection.
Results of this research suggest that both the St. Peter Sandstone and the Potosi Dolomite (a
formation of the Knox) reservoirs may be capable of storing up to 2 million tonnes of CO2
per year for a 20-year period. Reservoir simulation results for the St. Peter indicate good
injectivity and a relatively small CO2 plume. While a single St. Peter well is not likely to
achieve the targeted injection rate of 2 million tonnes/year, results of this study indicate that
development with three or four appropriately spaced wells may be sufficient. Reservoir
simulation of the Potosi suggest that much of the CO2 flows into and through relatively thin,
high permeability intervals, resulting in a large plume diameter compared with the St. Peter.

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