The Marcellus Shale contains about 84 trillion cubic feet of
undiscovered, technically recoverable natural gas and 3.4
billion bbl of undiscovered, technically recoverable natural
gas liquids according to a new assessment by the US Geological
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 cubic feet
of gas (TCF) and 0.01 billion bbl of natural
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 Marcellus Shale estimate is of unconventional (or
continuous-type) gas resources.
Since the 1930s, almost every well drilled through the
Marcellus found noticeable quantities of natural
gas. However, in late 2004, the Marcellus was recognized as
a potential reservoir rock, instead of just a regional source
rock, meaning that the gas could be produced from it instead of
just being a source for the gas.
Technological improvements resulted in commercially viable
production and the rapid development of a major, new
continuous natural gas and natural gas liquids play in the
Appalachian Basin, the oldest producing petroleum province in
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 TCF (95% to
5% probability, respectively), and the estimate of natural
gas liquids ranges from 1.6 to 6.2 billion bbl (95% to 5%
There are no conventional petroleum resources assessed in
the Marcellus Shale of the Appalachian Basin.
These new estimates are for technically recoverable oil and
gas resources, which are those quantities of oil and gas
producible using currently available technology and industry practices,
regardless of economic or accessibility considerations.
As such, these estimates include resources beneath both
onshore and offshore areas (such as Lake Erie) and beneath
areas where accessibility may be limited by policy and
regulations imposed by land managers and regulatory
The Marcellus Shale assessment covered areas in Kentucky,
Maryland, New York, Ohio, Pennsylvania, Tennessee, Virginia,
and West Virginia.
The USGS is the only provider of publicly available
estimates of undiscovered technically recoverable oil and gas
resources of onshore lands and offshore state waters, it
The USGS worked with the Pennsylvania Geological Survey, the
West Virginia Geological and Economic Survey, the Ohio
Geological Survey, and representatives from the oil and gas
industry and academia to develop an improved geologic
understanding of the Marcellus Shale.
The USGS Marcellus Shale assessment was undertaken as part
of a nationwide project assessing domestic petroleum
basins using standardized methodology and protocol.
The new assessment of the Marcellus Shale may be found here.