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ABSTRACT: Cambrian Paleotopographic and Structural Controls in the Southern Rose Run Fields, Eastern Ohio

Alan H. Coogan, Gustavo Lesser

Uppermost Cambrian strata of the Knox Dolomite Group in eastern Ohio produce gas from the Rose Run sandstone and the overlying Beekmantown Dolomite. In the study area (225 mi2; >150 control wells), the Rose Run reservoir thins from >50 ft in the northeast to <40 ft in the southwest by combined facies change and removal of the upper sands at the Knox Unconformity surface. The Beekmantown reservoirs are thin, very porous horizons in the thicker dolomites of the eastern, low-lying, hilly plateau (East Coshocton Hills). Isolated, dolomite-capped, remnant outliers (1-2 mi2) lie west of an escarpment where the unconformity surface cuts down to the west from the Beekmantown Dolomite into the underlying Rose Run sandstones in the valley of the Woost r Arch. Overlying Ordovician Glenwood Shale thins over prominent paleohills.

The pre-Ordovician folding of the southern field area preserved the East Coshocton Hills and outliers in synclinal folds, but erosion cut deep into the Beekmantown and Rose Run units over anticlinal valleys. The abrupt termination of the dolomite plateau to the west and north suggests fault control.

Three different "plays" are evident. Gas may be trapped on structure in porous Beekmantown Dolomite of the East Coshocton Hills. Dolomite-capped remnant hills may preserve a thicker section and enhance structure locally to trap gas in the underlying Rose Run sandstone. Finally, upper sandstone beds of the Rose Run may produce from immediately below the unconformity. The Ordovician Glenwood Shale is the main seal for these combined structural and stratigraphic traps.

AAPG Search and Discovery Article #90998 AAPG Eastern Section Meeting, London, Ontario, Canada, September 10-12, 1990