CITIZEN POWER ALLIANCE

The Energy Department said it will reduce its estimate of undiscovered natural gas in New York, Pennsylvania and other states following a report by the U.S. Geological Survey.

The USGS report, released Tuesday, estimates that the eight-state Marcellus Shale region contains some 84 trillion cubic feet of undiscovered, recoverable natural gas. That amount is far higher than the geological service had estimated in a 2002 report, but far below a recent projection by the Energy Department.

The conflicting reports prompted confusion and finger pointing amid growing questions about the extent of natural gas reserves available in the Marcellus region, which is in the midst of a drilling boom stretching from New York to West Virginia. Accurate estimates are important for drillers and regulators alike as the government increasingly examines the risks of natural gas. Improved geologic information and new drilling techniques, such as hydraulic fracturing, have opened up vast fields of previously out-of-reach supplies.