Reserve growth from 70 oil and natural gas accumulations in the United States -- excluding both Federal offshore areas and the nation's burgeoning shale plays -- has the potential to add 291 Tcf of natural gas, 32 billion bbl of oil and 10 billion bbl of natural gas liquids (NGLs) to domestic reserves, according to a new estimate by the U.S. Geological Survey (USGS).

"The combined Alaska and the Pacific Coast regions should have the greatest amount of oil reserve growth, whereas the Gulf Coast region should have the greatest amount of gas reserve growth," according to the estimate.

If achieved, the added reserves would constitute about 10% of the overall domestic oil and gas endowment, USGS said.

On a regional basis, USGS estimated that:

The estimates of volumes of technically recoverable, conventional petroleum resources were made using a new assessment methodology developed by USGS.

"Unlike past estimates of reserve growth that relied entirely on statistical extrapolations of growth trends, this assessment is based in part on detailed analysis of geology and engineering practices used in the assessed producing accumulations," USGS said.

USGS defines reserve growth as the increase in estimated volumes of oil and natural gas that can be recovered from discovered fields and reservoirs through time. Most reserve growth results from delineation of new reservoirs, field extensions or improved recovery techniques, thereby enhancing efficiency, and recalculation of reserves due to changing economic and operating conditions.

No attempt was made to estimate economically recoverable resources, and the estimate does not include resources in Federal offshore areas or any unconventional oil and gas accumulations, USGS said.

USGS currently estimates 27 billion bbl and 388 Tcf of undiscovered, technically recoverable conventional oil and gas resources from onshore and underlying state waters.

In June USGS said reserve growth for the world excluding the United States totaled 665 billion bbl of oil, 1,429 Tcf of gas and 16 billion bbl of NGL. Earlier this year a USGS analysis of resources in 171 geologic provinces, including Canada and Mexico and several Arctic provinces -- but excluding the United States -- found that the world holds an estimated 5,606 Tcf of undiscovered, technically recoverable conventional natural gas (see Daily GPI, April 20).

USGS recently said five Mesozoic shale basins along the East Coast collectively hold an estimated mean of nearly 3.9 Tcf in undiscovered natural gas and 135 million bbl of undiscovered NGLs (see Daily GPI, June 21). Other recent domestic assessments by USGS estimated approximately 84 Tcf of undiscovered, technically recoverable natural gas and 3.4 billion bbl of undiscovered, technically recoverable NGL in the Marcellus Shale (see Daily GPI, Aug. 29, 2011; Aug. 24, 2011), and 19 Tcf of undiscovered, technically recoverable gas, 600 million bbl of oil and 46 million bbl of NGL in Alaska's Cook Inlet region (see Daily GPI, June 30, 2011).

In about nine years the United States will be a net exporter of natural gas, according to an update from the U.S. Department of Energy's Energy Information Administration (see Daily GPI, Jan. 24).

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