CHARACTERIZATION OF THE CAMBRIAN EAU CLAIRE FORMATION AS CAPROCK FOR CARBON SEQUESTRATION INTO THE MOUNT SIMON SANDSTONE IN KENTUCKY
Geophysical logs are used to correlate carbonates and shales of the upper Conasauga Group eastward across the Grenville Front with the Eau Claire Formation. The study section is 300 to 900 ft thick, and can be subdivided into as many as eight intervals. In general, Conasauga carbonates thin westward into Eau Claire shales. Two intervals of shale, one at the base and one at the top (Nolichucky Formation of the Conasauga Group) of the Eau Claire are continuous across the study area. The lower shale interval has an average thickness of 30 ft, thickening westward. A single thick carbonate, the Davis Limestone of Indiana, occurs in the upper Eau Claire Formation as used in Kentucky.
Core samples of the Eau Claire are described from two wells in Kentucky. The DuPont No. 1 WAD well, located in Jefferson County, has 40 ft of core from the lower part of the Eau Claire. The core consists of alternating, medium gray shales and burrowed, slightly calcareous siltstones. Shales contain fragmented trilobite debris and small brachiopods. Burrows are small and mostly occur in the siltstones. A 50-ft core from a carbonate equivalent to the Davis Limestone consists of thrombolytic boundstones and oolitic grainstones. Grainstones exhibit variable porosity. The second well is the Battelle No. 1 Duke Energy well, Boone County, which was drilled as a CO2 injection test in the Mount Simon Sandstone. One 40 ft-core interval consists of alternating gray shales and calcareous, bioturbated siltstones. This well has more siltstones, and more fossil debris than the DuPont core. Very low permeability data for shales in both wells support the Eau Claire as acceptable caprock. Additional geochemical and mineralogical testing is ongoing to examine lateral variability and depositional history of the study interval.