PITTSBURGH (AP) -- The U. S. Geological Survey says the Marcellus Shale region contains some 84 trillion cubic feet of undiscovered, recoverable natural gas, far more than thought nearly a decade ago.
Tuesday's figure is much higher than the last government assessment in 2002, which suggested about 2 trillion cubic feet of recoverable gas.
The USGS says the estimate came from new information about the gas-rich formation underlying New York, Pennsylvania, Ohio and West Virginia. Technical improvements in how wells are drilled also contributed to the new estimate.
The agency estimates 3.4 billion barrels of undiscovered, recoverable natural gas liquids.
Thousands of wells have been drilled across Pennsylvania in the last few years, prompting excitement in the gas industry but concerns from environmental groups who fear the drilling process could poison water supplies.