These gas estimates are significantly more than the last USGS assessment of the Marcellus Shale in the Appalachian Basin in 2002, which estimated a mean of about 2 trillion ft3 of gas and 0.01 billion barrels of natural gas liquids.
The increase in undiscovered, technically recoverable resource is due to new geologic information and engineering data, as technological developments in producing unconventional resources have been significant in the last decade.
This USGS assessment is an estimate of continuous gas and natural gas liquid accumulations in the Middle Devonian Marcellus Shale of the Appalachian Basin. The estimate of undiscovered natural gas ranges from 43.0 to 144.1 trillion ft3 (95% to 5% probability, respectively), and the estimate of natural gas liquids ranges from 1.6 to 6.2 billion barrels (95% to 5% probability, respectively). There are no conventional petroleum resources assessed in the Marcellus Shale of the Appalachian Basin.
These new estimates only cover technically recoverable resources, which can be tapped using currently available technology and practices, these estimates include reserves both onshore and offshore and beneath areas which are not accessible due to regulatory measures.
The Marcellus Shale assessment covered areas in Kentucky, Maryland, New York, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia. The previous Marcellus Shale assessment can be found online.