OIL AND GAS PRODUCTION TRENDS AND THEIR RELATION TO THE DEPOSITIONAL FRAMEWORK OF THE MISSISSIPPIAN “BIG LIME”, SOUTHERN WEST VIRGINIA, USA

The Mississippian Greenbrier Limestone or “Big Lime” is an historic oil and gas producer in the Appalachian basin, with a majority of wells located in southern West Virginia. The Big Lime play consists of carbonate reservoir facies, including oolitic grainstone and skeletal grainstone to packstone shoals, bounded vertically and laterally by lagoonal, deep ramp, or slope-derived lime mudstones. These reservoirs continue to be economic targets, and the Big Lime is one of the many units in WV currently being completed utilizing advanced horizontal drilling and hydraulic fracturing techniques. Results from recent multi-stage horizontal completions show a high variability in production volume, with annual yields ranging from 16 to 65 MMcf for the first full year in production. None of the horizontal wells yielded oil, but oil production is reported from several locations within the study area. To assess this apparent variability in both well production and pay type, the West Virginia Geological and Economic Survey (WVGES) is conducting an analysis of oil and gas well data from several counties located within the play. Data include initial production and pressure test results taken from completion reports, annual production volumes, and geophysical log analysis of gamma-ray, density, resistivity, and PE logs to determine net-to-gross pay thickness, porosity-feet, water saturation, and relative permeability. Fairway maps were developed for major trends and compared to facies architecture and sequence stratigraphic framework studies from the literature. This integration of historic and modern well data, petrophysical analyses, facies distribution, and sequence stratigraphic architecture results in a more detailed reservoir characterization and enables operators to plan more efficient and effective drilling programs within a highly heterogeneous target.