The oil and gas areas of West Virginia, eastern Ohio and eastern Kentucky include the producing fields which cover the southern two-thirds of the Appalachian basin. The occurrence of oil and gas is associated directly with the cms tal movements which resulted in forming the basin, and accumulation is due to secondary structural features, minor folding and in the case of a part of eastern Kentucky, to faulting. All of these causes of accumulation are affected and modified by porosity, sand lensing and various local conditions, including water in the shallow horizons.
The lowest producing horizon stratigraphically is in the top of the Lower Ordovician system, and the highest is near the base of the Permian. In both, the yield is small. Major production occurs from the Conemaugh formation of Pennsylvanian age downward through the Mississippian and Upper Devonian series, with the Clinton sand of Silurian age ranking as a major producer in Ohio.