In the San Juan Basin of Mexico and Colorado, coalbed methane reserves soared to 24 TCF from 7 TCF.

Scientists said the Powder River Basin in Wyoming also contained about 14.3 TCF of coalbed methane gas, an increase of 1.1 TCF from the 1995 assessment. The increase in reserves is based upon new data from exploration and drilling operations.

The lucrative Power River has been subject to a series of lawsuits in recent months by environmental groups. They argue that at least three leases and potentially thousands of others are illegal because the government failed to thoroughly analyze the environmental impact of drilling.

Coalbed methane is a form of natural gas trapped beneath coal reserves and held in place by water pressure. Environmental groups contend that when the gas is removed, sodium in the water flows into streams, harming cattle and local residents.

Among the five regions, only the Greater Green River Basin in southwestern Wyoming posted a drop in reserves. Chris Schenk, a geologist with the USGS who lead the assessment, said unconventional gas, or reserves not held in place by water, dropped to 119 TCF from 85 TCF in southwestern Wyoming.

"Overall, coalbed methane is pretty good, that is the upside to these areas," said Schenk. "With better data you can just assess these things better."

The following are the average natural gas, oil and natural gas liquids found in the five geologic basins:

* Uinta-Piceance of Colorado and Utah-21 TCF natural gas, 60 million barrels (MMB) of oil, 43 MMB of natural gas liquids. Nearly all the undiscovered gas resource is unconventional.

*Southwestern Wyoming (Greater Green River Basin)-84.6 TCF natural gas, 131 million barrels of oil, 2600 MMB of natural gas liquids. Most of the undiscovered gas resource is unconventional.

*San Juan Basin of New Mexico and Colorado: 50.6 TCF natural gas, 19 million barrels of oil, 148 MMB of natural gas liquids. Nearly all the undiscovered gas resource is unconventional.

*Montana Thrust Belt: 8.6 TCF natural gas, 109 million barrels of oil, 240 MMB of natural gas liquids. All of the undiscovered gas resource is conventional.

*Powder River Basin of Wyoming and Montana: 16.5 TCF natural gas, 1600 MMB of oil, 86.5 MMB of natural gas liquids. Most of the undiscovered gas resource is unconventional.