STORAGE IN U.S. MIDCONTINENT CAMBRO-ORDOVICIAN CARBONATES: IMPLICATIONS OF THE WESTERN KENTUCKY CARBON STORAGE TEST

Results of the western Kentucky carbon storage test provide a basis for evaluating supercritical CO₂ storage in Cambro-Ordovician carbonate reservoirs throughout the U.S. Midcontinent. This test demonstrated that the Cambro-Ordovician Knox Group had reservoir properties suitable for supercritical CO₂ storage in a deep saline reservoir hosted in carbonate rocks, and that strata with properties sufficient for long-term confinement of supercritical CO₂ were present in the deep subsurface. The Kentucky Geological Survey No. 1 Marvin Blan well was drilled in 2009 after 18 months of planning, drillsite due diligence, and regulatory agency permitting. It reached a total depth of 8126 ft in Precambrian Middle Run Sandstone. A total of 395 ft of whole-diameter cores was cut in the well and an extensive suite of geophysical logs was recorded. The Ordovician Maquoketa Shale and Black River Group were cored to test their sealing capacity, and the Knox was cored to test its reservoir properties. Evaluation of well and core data indicated that the Knox had reservoir properties suitable for CO₂ storage, and that the overlying Maquoketa had sealing capacity sufficient for long-term confinement. Injection testing with brine and CO₂ was completed in two phases. The first phase tested the entire Knox in the open borehole at 3780–7397 ft, below casing cemented at 3660 ft, whereas the second phase tested a mechanically-isolated dolomitic-sandstone interval at 5038–5268 ft. Review of the No. 1 Marvin Blan and other wells drilled into the Knox suggests that much of the Midcontinent may have carbonate reservoirs with CO₂ storage potential. About half of the Midcontinent is underlain by a thick Cambro-Ordovician carbonate section correlative with the Knox, including the Arbuckle Formation in Kansas and Oklahoma and the Ellenburger Formation in Texas and New Mexico. These strata have been developed throughout the Midcontinent for oil and gas production, gas storage, and waste fluid injection. Successful CO₂ injection in the Knox suggests that deep saline reservoirs in these correlative carbonate strata may be prospective for CO₂ storage. Thus, large regions of the Midcontinent may be suitable for geosequestration where reservoirs and sealing intervals are sufficiently deep to ensure storage of supercritical-phase CO₂.