The Mississippian Greenbrier limestone, in southern West Virginia and eastern Kentucky, consists of interbedded layers of clastic and non-clastic limestone. In the area of investigation, it ranges from only a few feet to 1,200 feet in thickness.
Oil and gas of the Greenbrier limestone has been obtained from porosity in (1) oölitic zones, (2) dolomite zones, and (3) zones of oölitic, dolomitic, sandy limestone. Zones of oölitic limestone are common in the lower part of the Greenbrier limestone, especially near the lower limit of the formation. The oolites were apparently developed in shallow water near the shoreline at the extreme margins of the Greenbrier basin. The development of basal oölitic zones is most strongly governed by the topographic features existing on the pre-Greenbrier erosional surface of the underlying Maccrady Formation. The basal oölitic zones are elongate in a direction parallel with the ancient shoreline which is, in turn, parallel with the isopach contours drawn on the total thickness of the Greenbrier limestone.
The uppermost members of the Greenbrier limestone are time-equivalent and apparently were deposited contemporaneously over an extensive area in southern West Virginia and eastern Kentucky. The clastic and dolomitic zone at or near the base of the Greenbrier limestone crosses time lines and becomes progressively older toward the axis of the basin of deposition.
The presence of hydrocarbons within the oölitic zones soon after deposition may have prevented their complete cementation by excluding mineralized solutions from the available interstitial porosity within the sediments.