The U.S. possesses a total technically recoverable resource base of 2,515 trillion cubic feet (Tcf) as of year-end 2014, a 5.5% increase from 2012, according to the latest biennial assessment by the Potential Gas Committee (PGC), based in Golden, Colo.

The evaluation is the highest resource tally in the committee’s 50-year history, exceeding the previous high assessment in 2012 by 131 Tcf. The revised figure comes from reevaluations of shale gas resources in the Atlantic, Midcontinent, Gulf Coast and Rocky Mountain areas and conventional/tight gas resources in the Midcontinent and Rockies.

These changes were assessed in addition to 53 Tcf of domestic marketed-gas production estimated by the U.S. Energy Information Administration for the two-year period since the committee’s previous assessment.

“The PGC’s year-end 2014 assessment reaffirms the committee’s conviction that abundant, recoverable natural gas resources exist within our borders, both onshore and offshore, and in all types of reservoirs — from conventional, ‘tight’ and shales, to coals,” said John B. Curtis, Ph.D., professor emeritus of geology and geological engineering at the Colorado School of Mines and director of the Potential Gas Agency. The agency provides guidance and technical assistance to the PGC.

Curtis cautioned that the current assessment assumes neither a time schedule nor a specific market price for the discovery and production of future gas supply.

The committee’s year-end 2014 assessment includes 2,357 Tcf of gas potentially recoverable from “traditional” reservoirs such as conventional, tight sands and carbonates and shales. Another 158 Tcf is in coalbed reservoirs.

Compared to year-end 2012, assessed traditional resources increased by 131.2 Tcf (5.9%), while coalbed gas resources declined by a nominal 0.2 Tcf (0.1%), resulting in a net increase in total potential resources of 131 Tcf (5.5%).

The U.S. Department of Energy’s latest available determination of proved reserves found 338 Tcf (dry gas) as of year-end 2013. Combined with PGC’s assessments of technically recoverable resources the U.S. has a total available future supply of 2,853 Tcf, an increase of 161 Tcf over the previous evaluation.

Knowledge the technically recoverable gas continues to improve with each assessment, Curtis said.

“New and advanced exploration, well drilling, completion and stimulation technologies are allowing us increasingly better delineation of and access to domestic gas resources—especially ‘unconventional’ gas—which, not all that long ago, were considered impractical or uneconomical to pursue,” Curtis said.

The present assessment, strengthened by robust domestic production levels and reserves bookings, indicates an “exceptionally strong” and optimistic gas supply picture for the nation, he said.

Increases in Appalachian Basin shale gas assessments, continues to rank the Atlantic area as the country’s richest resource area with 35% of total U.S. traditional resources. It is followed by the Gulf Coast (including the Gulf of Mexico), Rocky Mountains and the Midcontinent.

The increased assessment in 2014 from 2012 arose primarily from analyses of recent drilling, well-test and production data from the four regions. The largest volumetric and percentage gains were reported for Appalachian shales, primarily the Marcellus Shale but also the Utica and the newly assessed Rogersville Shale. Collectively they rose by 137 Tcf (24%).

Gulf Coast assessments rose by 15 Tcf (3%), reflecting continued aggressive development of wet gas and condensate in the prolific Eagle Ford Shale of the Texas Gulf Coast Basin and a first-time assessment for the Cretaceous Tuscaloosa Marine Shale in Louisiana.

In the Midcontinent, modest declines in assessments for the Arkoma and Anadarko basins (conventional reservoirs and shales) were offset by substantially higher evaluations of the Barnett Shale in the Fort Worth Basin and the stacked pays of the Bone Spring and Wolfcamp plays in the Permian Basin. The area’s total assessment gained 26.9 Tcf (10%).

The Rocky Mountain area’s 9.6-Tcf (2.3%) net increase resulted from reevaluation of new data and drilling results from the Cretaceous Niobrara Shale play in western Colorado’s Piceance Basin and the Niobrara fractured-carbonate play in the Denver Basin.

Shale gas grow nationwide is continuing to prop up what was, just a decade ago, a resource thought extinguished. The PGC’s total assessed shale gas resource of 1,253 Tcf in 2014 accounts for approximately 61% of the country’s total traditional potential resources, up 57% from 2012.