USGS boosts assessment of recoverable natural gas in Marcellus Shale by 42x from 2002; now 84 trillion cubic feet
|Map of the Appalachian Basin Province showing the three Marcellus Shale assessment units. 96% of the estimated resource resides within the Interior Marcellus AU. Source: USGS. Click to enlarge.|
The Marcellus Shale contains about 84.198 trillion cubic feet (TCF) of undiscovered, technically recoverable natural gas and 3.379 billion barrels of undiscovered, technically recoverable natural gas liquids, according to a new geology-based assessment by the US Geological Survey (USGS). Technically recoverable oil and gas resources are those quantities of oil and gas producible using currently available technology and industry practices, regardless of economic or accessibility considerations.
These gas estimates are significantly higher 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 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 (e.g., the fracking boom) have been significant in the last decade, USGS says.
|USGS vs. EIA/INTEK estimates|
|While the new 84 TCF USGS assessment marks a significant increase from the 2002 report, it is also considerably less than an estimate developed by INTEK, under a commission from the US Energy Information Administration, published in July that pegged Marcellus technically recoverable shale gas resources at 410.3 TCF.|
|INTEK developed its resource estimates from publicly available company data and commercial databases for wells and acreage currently in production. The estimates of technically recoverable resources are based on the area, well spacing, and average expected ultimate recovery (EUR) for each shale play or subportion of the play.|
|Overall, INTEK estimated total on-shore recoverable shale gas resources for the lower 48 states at 750 TCF. That 750 trillion cubic feet of shale gas resources is, however, a subset of the EIA’s AEO2011 onshore Lower 48 States natural gas shale technically recoverable resource estimate of 862 trillion cubic feet.|
|In November 2010, EIA had reported proved shale gas reserves for the Marcellus play of 4.478 TCF for 2009. EIA defines proved reserves as those volumes of oil and natural gas that geologic and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions.|
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 gas 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 the United States.
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 barrels (95% to 5% probability, respectively). There are no conventional petroleum resources assessed in the Marcellus Shale of the Appalachian Basin.
The entire undiscovered gas and natural gas liquids resource is in a continuous accumulation and is contained within a single TPS (total petroleum system), the Devonian Shale-Middle and Upper Paleozoic TPS.
The Marcellus Shale is divided into three assessment units (AUs) within the Appalachian Basin—the Western Margin Marcellus AU, which encompasses the western extent of the formation and west of the Appalachian Structural Front (ASF); the Interior Marcellus AU, which is the central extent of the trend and west of the ASF; and the Foldbelt Marcellus AU, which is east of the ASF. The total area of these three AUs extends from southern New York to northeastern Tennessee and from central Ohio to western Virginia and Maryland.
Ninety-six percent of the estimated resource resides within the Interior Marcellus AU.
The Interior Marcellus AU contains the Marcellus Shale that is 50 feet thick or more; ranges in depth from less than 2,000 ft to more than 11,000 ft; and contains strata that range in current levels of thermal maturity from peak oil to past-peak gas.
USGS is the only provider of publicly available estimates of undiscovered technically recoverable oil and gas resources of onshore lands and offshore state waters. 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.
USGS will update its 2008 estimate of undiscovered, technically recoverable oil and gas in the US portion of the Bakken Formation, an important domestic petroleum resource located in North Dakota and Montana beginning in Fiscal Year 2012.
Coleman, J.L., Milici, R.C., Cook, T.A., Charpentier, R.R., Kirshbaum, Mark, Klett, T.R., Pollastro, R.M., and Schenk, C.J. (2011) Assessment of undiscovered oil and gas resources of the Devonian Marcellus Shale of the Appalachian Basin province, 2011: US Geological Survey