US natural gas resources at 2,385 tcf

Potential Gas Committee reports no change for Alaska; year-end 2012 total up 486 tcf from ’10, mostly from shale gas resources

Kristen Nelson

Petroleum News

The latest biennial assessment of U.S. natural gas resources by the Potential Gas Committee shows a technically recoverable resource base of 2,384 trillion cubic feet, the highest resource evaluation in the 48-year history of the PGC, with most of the increase “from new evaluations of shale gas resources in the Atlantic, Rocky Mountain and Gulf Coast areas,” PGC said in an April 9 release.

The Potential Gas Committee has been doing biennial assessments since 1964 of technically recoverable U.S. natural gas. PGC is a nonprofit with volunteer geoscientists and petroleum engineers who work in the natural gas exploration, production, transportation and distribution industries, as well as in the field and technical services and consulting sectors. The committee has input from technical advisors and observers from federal and state government agencies, academia, industry and research organization in the U.S. and Canada and is supported by the Potential Gas Agency at the Colorado School of Mines. The agency receives financial support from prominent E&P and gas pipeline companies and distributors.

Slide information from the PGC for 1999 through 2012 demonstrates the impact of shale gas on total potential gas resources.

From 1990 through 2004, total traditional gas resources plus a relatively small amount of coalbed gas resources ranged from means of 1,003 tcf in 1990 to a peak of 1,127 tcf in 2004 and down marginally to 1,119 tcf in 2004.

In 2006 some 200 tcf of shale gas was added, pushing the total of 1,321 tcf. In 2008 shale gas added 615.9 tcf to the total, which was 1,836 tcf that year. Shale gas grew to 686.6 tcf in 2010, and the total to 1,898 tcf.

In the 2012 figures, shale gas had grown to 1,073 tcf — more than the total for all gas resources in the years 1990 through 1998 — and the total to 2,384 tcf.

With the addition of proved gas reserves from the Energy Information Administration of 304.6 tcf, the committee puts the future gas supply at 2,688.5 tcf.

Proved reserves are known gas reservoirs under existing economic conditions and existing operating conditions, PGA said in its slide presentation, contrasted to resources, which include discovered and undiscovered gas and are subject to the effects of technology.

The committee listed no increase in Alaska resources, estimated at 193.8 tcf, between 2010 and 2012.

John B. Curtis, professor of geology and geological engineering at the Colorado School of Mines and director of the Potential Gas Agency, said in a statement that neither a time schedule nor a market price is assumed for discovery and production of future gas supplies.

“Assessments of the Potential Gas Committee represent our best understanding of the geological endowment of the technically recoverable natural gas resource of the United States,” Curtis said.

The Atlantic area is now ranked as the nation’s richest natural gas resource area with 33 percent of U.S. traditional resources. A substantial increase in Appalachian basin shale gas pushed the Atlantic area to the top of the PGC’s list, at 741.3 tcf, followed by the Gulf Coast at 521 tcf, the Rocky Mountain area at 421.3 tcf, the Mid-Continent at 269.5 tcf, Alaska at 193.8 tcf, the Pacific area at 54.4 tcf and North Central at 20.8 tcf. Total U.S. coalbed gas resources are 158.2 tcf.

The PGC said total assessment changes from 2010 to 2012 are primarily due to changes in the Atlantic, Gulf Coast and Rocky Mountain areas, which combined account for 76 percent of assessed total traditional resource.

Increases in the Atlantic area were primarily due to increases in the Marcellus in the Appalachian basin, but also included other Devonian shales and the Utica, which together accounted for an increase of 335 tcf, 147 percent.

There was also a substantial 58 percent increase, 21.6 tcf, in the Eagle Ford shale in the Texas Gulf Coast basin.

The PGC said that the 2012 shale gas resource of 1,073 tcf accounts for some 48 percent of total traditional potential resources.