COLUMBUS, Ohio — National gas reserves in the United States are much bigger than previously thought, according to a report released Thursday.

COLUMBUS, Ohio — National gas reserves in the United States are much bigger than previously thought, according to a report released Thursday.

The Potential Gas Committee in Golden, Colorado, said that the estimated U.S. reserves are 35 percent higher than just two years ago, thanks to new technology that has allowed producers to drill for gas in shale rock.

As a result, reserves levels have reached the highest level since the group started tracking the information 44 years ago.

The report comes as natural gas is being touted as a way to help reduce U.S. dependence on foreign oil and cut emissions that lead to global warming.

"We knew it was there. It was a matter of how productive it possibly could be," said John Curtis, professor of geology and geological engineering at the Colorado School of Mines and the committee director.

The committee, a volunteer group backed by natural gas producers and utilities, estimated the country's total natural gas resources at 2,074 trillion cubic feet, an increase of 542 trillion cubic feet from its last report.

The figure includes 238 trillion cubic feet of proven gas reserves as established by the Department of Energy and 1,836 trillion cubic feet of reserves it labeled as probable, possible, and speculative.

The report is similar to a study prepared last summer for the natural gas-backed American Clean Skies Foundation that found the country had 2,247 trillion cubic feet of natural gas reserves — a 118-year supply at 2007 production levels. The U.S. consumes about 20 billion cubic feet of gas per year.

Natural gas is used to generate about a fifth of the nation's electricity as well as to heat homes. It emits about half of the heat-trapping greenhouse gas that coal does.

Thursday's report said shale now makes up one-third of the 1,836 trillion cubic feet of potential resources, much of it from a re-evaluation of shale gas in the Appalachian basin and the Mid-Continent region, Gulf coast and Rocky Mountain areas.

Shale is a kind of layered, sedimentary rock that exists in formations throughout the world. In the U.S., gas production from shale dates back to the 1800s.

But the gas, tightly locked in rock formations, had been extraordinarily expensive to extract. That began to change about 15 years ago as producers developed new techniques such as horizontal drilling, where the drill is turned in a right angle to bore into a gas reservoir horizontally.

Gas from shale now amounts to about 5 percent of total U.S. production, according to the Gas Technology Institute.

The report Thursday comes as producers have slashed production of natural gas as demand along with prices have crashed nearly 70 percent since last summer from $13.69 per 1,000 cubic feet to about $4.30 per 1,000 cubic feet.