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The Knox Group: A Potential Saline Reservoir for Carbon Sequestration in the Eastern Midcontinent

James A. Drahovzal1, Stephen F. Greb1, David C. Harris1, Michael P.Solis1, Lawrence H. Wickstrom2, and Brandon C. Nuttall1

1Kentucky Geological Survey, University of Kentucky, Lexington, KY 40506-0107

2Ohio Division of Geological Survey, Columbus, OH 43229

In the eastern Midcontinent, the Knox Group is divided into the upper (Ordovician) Beekmantown Dolomite and the lower (Cambrian) Copper Ridge Dolomite and their equivalents. The group is composed of several thousand feet of dominantly dense, impervious dolomites that are generally considered, along with the Conasauga Formation, to be the regional seal for carbon sequestration projects in the underlying Mount Simon Sandstone

The Knox, however, has numerous thin zones of high porosity throughout its vertical extent and could constitute an important sequestration target, especially in those instances where the Mount Simon may be missing or of low permeability. One example of this is in the DuPont waste injection well at Louisville, Ky. Here, 400 feet of Mount Simon proved to be of insufficient injectivity and was abandoned in favor of a highly permeable vuggy dolomite facies in the Copper Ridge. Injectivity tests in the dolomite were as high as 150 gallons per minute, equivalent to injecting about 48 million tonnes of supercritical CO 2 annually.

The extent of porous zones in the Knox is variable, but they are noted throughout much of the interval in Indiana, Kentucky, and Ohio In this region, several gas storage fields exist in Knox porous zones. Likewise, oil fields along the Cincinnati Arch are developed in Knox breccias, fractures, and paleokarst zones. These scattered porosity zones are usually relatively thin and are confined both above and below by dense carbonates, making them potential carbon sequestration targets, that together have both high permeabilities and confining seals.

AAPG Search and Discovery Article #90059©2006 AAPG Eastern Section Meeting, Buffalo, New York