Southwestern Energy Company engages in the exploration, development and production of natural gas, crude oil and natural gas liquids in the United States. It holds significant properties in the prolific Appalachian Basin, which is famous for its natural gas reservoirs. Southwestern Energy is involved in the development of an unconventional gas reservoir located Pennsylvania and West Virginia. The company's operations in northeast Pennsylvania, which includes unconventional natural gas reservoir known of the Marcellus Shale are referred to as Northeast Appalachia. Its West Virginia and southwest Pennsylvania operations, which incorporates unconventional natural gas, oil and NGL reservoirs in Marcellus Shale, Utica and the Upper Devonian, are referred to as Southwest Appalachia.