The U.S. Geological Survey recently released an updated survey on recoverable reserves in the Marcellus. From The Hill: "According to the updated USGS mean estimate, the area contains 84 trillion cubic feet of technically recoverable natural gas and 3.4 billion barrels of natural gas liquids. *** The new estimate for the Marcellus Shale — which includes portions of New York, West Virginia and other states — is far higher than the 2002 survey, when the mean estimate was 2 trillion cubic feet of natural gas and 10 million barrels of natural gas liquids." However, according to Bloomberg: "The U.S. will slash its estimate of undiscovered Marcellus Shale natural gas by as much as 80 percent after a updated assessment by government geologists."
You can find a copy of the updated survey here.