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Detecting Porosity in Cambrian-Ordovician Beekmantown Dolomite: Examples of Three Producing Fields in East-Central Ohio

Roth, Bryan L.
Roth Exploration Geoservices, Williamsburg, MI

Cambrian-Ordovician Beekmantown dolomite can be a prolific oil and gas producer. Interpreting accurate thickness and detecting porosity within well-known units of the Beekmantown dolomite increases the probability of finding economic reserves and saves money by eliminating dry holes. Seismic interpretation methods to detect porosity are limited to the first couple hundred feet of Beekmantown dolomite at the Knox Unconformity, encompassing the stratigraphically ascending “A” and/or “B” porosity zones. Porosity detection techniques included are wavelet identification, isochron measurements, seismic modeling, seismic attribute display, amplitude graphing, complex seismic attribute/well log analysis and offset range stacks. Common interpretation mistakes are included to show potential costly pitfalls. Seismic examples from the Bakersville field, the Sharon Valley field (Holmes Limestone 1 well) and the Bloomfield field (Badertscher 1 well) show unique and related seismic characteristics defined by Beekmantown rock thickness, porosity, and structural geometry. At the Bakersville field, no single seismic measurement unanimously correlated with known geology and/or production, mainly because of the relatively thin Beekmantown dolomite (50-100 feet). At the Sharon Valley and Bloomfield fields, Beekmantown thickness (140-240 feet) is accurately measured from seismic data and porosity detection is good after some geology/seismic calibration. Beekmantown thickness is best determined by wavelet isochron measurements while porosity is best detected by amplitude measurements and offset range stacks.

AAPG Search and Discovery Article #90031©2004 AAPG Eastern Section Meeting, Columbus, Ohio, October 3-5, 2004