Statistics from the Energy Information Administration, the U.S. Energy Department's collector and analyzer of data on energy information, contained sharply lower approximations of known non-Alaskan natural gas resources.
The agency said the latest estimate is there are 482 trillion cubic feet of available shale gas in the United States, down 40 percent from the 2011 estimate of 827 trillion cubic feet, The New York Times reported Saturday.
The report also said the Marcellus region, a rock formation stretching from New York to West Virginia, contains 141 trillion cubic feet of gas, a 66 percent drop from last year's estimate of 410 trillion cubic feet. That means the region holds a six-year supply of natural gas, not the 17 years previously estimated.
Shale gas is extracted through hydraulic fracturing, or hydrofracking, a drilling technology that has drawn opposition from environmentalists.
Alaska holds trillions of cubic feet of conventional natural gas under its environmentally sensitive North Slope but lacks a pipeline to get it to market, the Times reported.
The EIA said the downward projections are the result of more and better information.
"Drilling in the Marcellus accelerated rapidly in 2010 and 2011 so that there is far more information available today than a year ago," the Times quoted the report as saying.