The Appalachian basin of the petroleum geologist, the birthplace of the oil industry, covers an area in the eastern United States of about 208,660 sq mi (540,450 sq km), which is divided into the oil-productive Appalachian Plateau segment of 172,000 sq mi (424,300 sq km) and the less favorable, structurally complex Valley and Ridge segment of 45,000 sq mi (116,000 sq km). The Appalachian basin contains at least 350,000 cu mi (1,460,000 cu km) of Paleozoic sedimentary rock, almost equally divided between the plateaus and the Valley and Ridge segments.

More than 2.5 × 10⁹ bbl of oil has been produced almost exclusively from the rocks of the plateau segment; more than half of this volume, about 1.68 × 10⁹ bbl has been extracted from Devonian rocks at depths of less than 1 mi (1.6 km).

Remaining reserves producible by present methods at existing prices for crude oil are estimated to range from 2.6 × 10⁶ to 3.4 × 10⁶ bbl, an amount slightly larger than one tenth the volume produced in the past 113 years. In contrast, the amount of oil originally in place that remains after efforts to extract it, is estimated to range from 10 × 10⁹ to 12 × 10⁹ bbl. Most of this oil, however, is locked in and economically unproducible by existing methods. Recovery of even a modest fraction of this oil will require (1) extensive drilling in the deeper, largely untested parts of the Appalachian Plateau segment of the basin; (2) exploration in the more favorable parts of the Valley and Ridge segment; (3) drilling offshore in ake Erie; (4) application of established secondary- and tertiary-recovery methods to old and long abandoned producing areas; and (5) the development of new and imaginative techniques to extract more of the remaining oil from the rocks of the Appalachian basin.

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