PRECAMBRIAN MIDDLE RUN SANDSTONE IN WESTERN KENTUCKY: RESULTS FROM THE KENTUCKY GEOLOGICAL SURVEY #1 MARVIN BLAN CO2 SEQUESTRATION TEST WELL

Precambrian strata in western Kentucky are poorly known from electric logs from a limited number of penetrations and recovered drill cuttings. Precambrian Middle Run Sandstone was cored in the Kentucky Geological Survey #1 Marvin Blan test well, Hancock County, Kentucky, to evaluate the CO₂ sequestration potential of pre-Mount Simon Sandstone strata. The Middle Run was penetrated at 7584–8126 ft (2312–2477 m) TD, and an oriented core was cut at 8000–8030 ft (2438–2448 m). The Middle Run is a brick-red, fine-grained, lithic arkose, with an illite clay matrix, and hematite cement. About 30% of grains are lithic fragments derived from underlying granite-rhyolite province igneous rocks and sparse grains of metamorphic rocks derived from Grenville basement. Quartz and feldspar grains are angular suggesting a local source, whereas lithic grains are rounded, suggesting a more distant source. Quartz grains show partial dissolution and authegenic overgrowths at their boundaries in thin sections. Structural dip in the Middle Run is 10° north. Several generations of east-dipping, microcrystalline quartz-filled fractures are evident in the cores. The nearest well to penetrate Precambrian strata, the KY Operating Company #1 Braden well located 16 mi (26 km) to the southeast in Breckinridge County, drilled 468 ft (143 m) of rhyolite below the Middle Cambrian unconformity. Interpretation of 2-D reflection seismic data suggests the Middle Run section under the #1 Marvin Blan well is 4500 ft (1372 m) thick and pinches out to the south on the older rhyolite basement. Sedimentary structures evident in the core include tidal laminations, crossbeds, flaser bedding, reactivation surfaces, scours, and mudstone ripup clasts and edgewise conglomerates, suggesting deposition on a sandy tidal flat. Paleotransport analysis of restored crossbed foresets suggests westerly transport across the tidal flat toward the East Continent Rift basin in meandering channels, approximately perpendicular to the Grenville front. Horizontal and vertical porosity and permeability were measured in three core plugs. Porosity averaged 1.35% and permeability averaged 0.00023 md, with horizontal and vertical values being approximately equal for both measurements. Therefore, the Middle Run in this area has no potential as a CO₂ sequestration reservoir.