Assessment of Undiscovered Gas Resources in the Middle Devonian Marcellus Shale of the Appalachian Basin Province

The U.S. Geological Survey (USGS) conducted a geology-based assessment and determined an estimated mean undiscovered natural gas resource of 84,198 billion cubic feet, along with a mean undiscovered natural gas liquids resource of 3,379 million barrels in the Devonian Marcellus Shale located in the Appalachian Basin Province. This province spans parts of ten eastern U.S. states, including Alabama, Georgia, and New York, among others. The Marcellus Shale's significance as a petroleum source stems from its geological components, including its richness as a source rock and its properties as a reservoir rock, classifying it as a continuous petroleum accumulation. The USGS identified one Total Petroleum System (TPS) and three assessment units (AUs) within this system, wherein 96% of the estimated resource is found in the Interior Marcellus AU.

This formation in the Appalachian Basin is segmented into three primary assessment units: the Western Margin Marcellus AU, the Interior Marcellus AU, and the Foldbelt Marcellus AU. These units stretch from southern New York to northeastern Tennessee, and from central Ohio to the west of Virginia and Maryland. While the Western Margin Marcellus AU represents the thinner and less mature section of the formation, the Interior Marcellus AU houses the most significant portion of the resource, characterized by thicker shale and varied depths. The Foldbelt Marcellus AU represents the shale found within the Appalachian fold and thrust belt, showcasing diverse thickness and depth, and varying levels of thermal maturity.