WASHINGTON, Aug. 24 (UPI) -- The U.S. Geological Survey said its survey of the Marcellus Shale deposit in the Appalachian Basin finds significantly more gas than its last review in 2002.
The USGS said it the shale deposit contains roughly 84 trillion cubic feet of undiscovered, technically recoverable natural gas and 3.4 billion barrels of undiscovered, technically recoverable natural gas liquids.
The USGS noted those estimates are "significantly" greater than the survey of the deposit in 2002.
"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," the agency said in a statement.
Energy companies use a process called hydraulic fracturing to get natural gas out of shale formations. Critics say the process, known as fracking, exposes groundwater aquifers to harmful chemicals, something energy companies and some state agencies dispute.
The U.S Department of Energy and some U.S. states with significant shale gas deposits are proposing new disclosure regulations to allay public concerns.
The USGS said nearly every well drilled in the Marcellus Shale formation since the 1930s uncovered "noticeable quantities" of natural gas.