A new surge of drilling activity is under way in Pennsylvania, with significant development and exploration for oil and gas reserves in the Upper Devonian sandstones.

Upper Devonian sedimentary rocks are present throughout 80 percent of the Commonwealth. Their origin can be traced to an eastern upland source area "Appalachia" that was elevated, possibly as a result of spasmatic collisions of the North American and North African continental plates during the Acadian orogeny. The clastic deposits spread from this eastern source area as a thick wedge of delta-plain redbeds of continental origin and merged westward into the "Chemung" marine facies.

Oil and gas accumulated in the sand deposits of the "Chemung" facies which are distributed in a northeast-southwest trending belt in western Pennsylvania. Over 500 oil and gas fields lie within this petroliferous belt. Cumulative production has exceeded 1.2 billion bbl of oil and 8.5 Tcf of gas.

Recent new-pool discoveries and successful pool-extension tests in eastern Indiana, Cambria, southern Westmoreland, and Butler Counties, plus untested Upper Devonian sands encountered during deep drilling operations in Westmoreland and Somerset Counties, will provide new areas for gas exploration and development in Pennsylvania.

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