Evaluation of Infill Drilling Potential of the Beekmantown Formation, Bakersville Field, Coshocton County, Ohio
Authors: Yeager Donald L. , Frantz Joseph H. , Moody Mark A. , Neese Mark A. 
Published: December 2007

We determined the infill drilling potential for a portion of the Bakersville Field (Beekmantown formation), Coshocton County, Ohio using an integrated reservoir engineering/geologic study. Well logs, completion reports, production data, and pressure buildup data were evaluated to calculate original gas in place, estimate and map net pay thickness, calculate permeability and skin factors, estimate current reservoir pressure, and estimate effective drainage areas in a four section area of the field. With the resultant drainage area calculations indicating the existing wells are effectively recovering the gas in place, potential infill locations offsetting highly productive Beekmantown completions are likely to encounter reservoir pressures significantly lower than the original 3,100 psia. Based on the results of this study, the operator chose not to participate in some proposed infill wells, thereby eliminating unnecessary capital expenditures.

Geology

The Bakersville Field produces from the Beekmantown Dolomite of Cambro-Ordovician age. Deposited over the Rose Run sandstone (the only laterally persistent sandstone unit within the Knox group), the Beekmantown is generally a fine-to-medium crystalline, non-permeable dolomite. The reservoir within the Beekmantown formation from which the Bakersville Field produces is a 2 to 6 ft interval of vugular and intergranular porosity commonly referred to as the "A" porosity zone. The "A" porosity zone is located approximately 70 ft above the top of the Rose Run sandstone. Hydrocarbon accumulation in the Bakersville Field was controlled by post-Knox structure in the area in conjunction with the truncation of this zone to the west by the Knox unconformity.

Development of the "A" porosity zone probably resulted form its unique depositional environment and resultant susceptibility to groundwater leaching. Core analyses, though sparse, suggest that the "A" zone may represent a sabkha-type environment during which evaporite minerals, especially gypsum or anhydrite, precipitated. During the time of post-Knox erosion, this zone was subjected to dissolution, which resulted in the excellent porosity/permeability of the "A" zone in the Bakersville Field.

Development History

The Bakersville Field, located in Coshocton County, Ohio (Fig. 1), produces from the Beekmantown and Clinton formations. Our study focused on the Beekmantown "A" porosity zone completions located in Sections 1, 2, 9, and 10, respectively. Discovered in 1980 with the drilling and completion of the Mizer #1 well, field development continued through 1991. The current average well spacing is approximately 118 acres in the four section area with the highest well density in Section 1 at 70 acres per well. Identified in this evaluation as a thin (5 to 6 ft), high permeability/porosity, single-layer gas reservoir, the Beekmantown producers effectively completed to this layer exhibit flow rates of up to 1.00 MMscf/D and cumulative recoveries up to 3.0 Bcf of gas. Beekmantown completions that did not encounter (or were not effectively completed in) the high permeability/porosity zone exhibit flow rates on the order of 10 Mscf/D and recoveries in the range of 30 MMcf of gas. Proposed future field development is based on 3-D seismic interpretation targeting both outlying and interior portions of the field.

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