WASHINGTON — U.S. proved crude oil and natural gas reserves achieved record annual volumetric increases in 2010 according to U.S. Crude Oil, Natural Gas, and Natural Gas Liquids Reserves, 2010, released by the U.S. Energy Information Administration (EIA).

Shale gas

“The use of horizontal drilling and hydraulic fracturing in shale and other tight rock formations played an important role in the increase of oil and natural gas reserves,” said EIA Administrator Adam Sieminski.

“For both oil and natural gas, these reserves increases underscore the potential of a growing role for domestically produced hydrocarbons in meeting current and projected U.S. energy demand.”

Proved oil reserves, which include crude oil and lease condensate, increased by 13 percent in 2010 to 25.2 billion barrels, marking the second consecutive annual increase and the highest volume of proved reserves since 1991.

Oil reserves

Texas recorded the largest volumetric increase in proved oil reserves among individual states, largely because of ongoing development in the Permian and Western Gulf Basins, while North Dakota had the second largest increase, driven by development activity in the Bakken formation in the Williston Basin.

Natural gas reserves

Natural gas proved reserves, estimated as “wet” gas that includes natural gas plant liquids, increased by 12 percent in 2010 to 317.6 trillion cubic feet (Tcf), the 12th consecutive annual increase and the first year U.S. reserves surpassed 300 Tcf.

Texas also led the nation in additions of natural gas proved reserves, primarily because of continued development of the Barnett and Haynesville/Bossier shale formations. Louisiana had the second largest volumetric increase, largely the result of ongoing development activity in the Haynesville shale formation.

In Pennsylvania, accelerated drilling programs in the Marcellus shale formation more than doubled the state’s year-end 2009 volumes.

Horizontal drilling

Contributing to the increases for both oil and natural gas proved reserves was the expanding application of horizontal drilling and hydraulic fracturing in shale and other “tight” (very low permeability) formations.

Another important factor for each fuel — particularly oil — was a higher price used to assess economic viability relative to the prices used for the 2009 reporting year.

Proved reserves are those volumes of oil and natural gas that geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions.

EIA’s estimates of proved reserves are based on an annual survey of about 1,200 domestic oil and gas well operators.