EXPLORATION TARGETS IN THE SOUTHERN APPALACHIAN BASIN

The southern Appalachian basin is separated into three provinces (Highland Rim, Cumberland Plateau, and Valley and Ridge). These provinces have been prospected for nearly two centuries with limited success because regionally the reserves are small, limited basement data leading to an incomplete geologic model, and very sparse well and seismic coverage. In the Valley and Ridge, the few wells drilled primarily target gas in the Sevier Shale and oil in the Middle Ordovician carbonates (i.e., Swan Creek field and Eureka structure). Potentially shallow targets and low leasing costs make it desirable to test structures in this region, but very few have been tested. The Cumberland Plateau, however, has been heavily drilled, but most of the drilling is clustered in a few counties. Prospecting has usually been based on “feel” rather than on following a model. There are numerous drilling targets in the Plateau; some of the most common drilling targets are gas from Pennsylvanian coal seams, oil and gas from Mississippian limestones, gas from the Chattanooga Shale, oil from the Middle Ordovician carbonates, and gas from the Upper Knox Group. Few deep tests have been conducted in the area because of the large amount of shallower pay horizons. Deep potential gas (i.e., in the Rome trough in Kentucky and Tennessee) and possible hydrothermal plays are present in the region, but the paucity of seismic data makes difficult any justification for large-scale exploration of these plays. The absence of prospecting has also greatly hindered development of a geologic model for the southern Cumberland Plateau, especially west of the Sequatchie anticline. In the Highland Rim, most of the prospecting is focused on regionally large oil and gas reserves found in the Middle Ordovician carbonates; with drilling depth being around 1,500 ft, it is not surprising that most of the recent prospecting in the southern Appalachian basin is done in this region.