U.S. crude oil proved reserves, led by reserve additions in Texas and North Dakota, increased at a record pace in 2012 according to the U.S. Crude Oil and Natural Gas Proved Reserves, 2012 report released by the EIA. Despite notable gains in the Marcellus and Eagle Ford shale gas plays, low natural gas prices drove down natural gas proved reserves in 2012, ending a 14-year run of consecutive increases in gas reserves.
Proved reserves are estimated quantities of energy sources that analysis of geological and engineering data demonstrate with reasonable certainty to be recoverable in future years from known reservoirs under existing economic and operating conditions. Significant year-to-year price changes can directly affect the "existing economic" metric.
Proved oil reserves, which include crude oil and lease condensate, increased 15.4% in 2012 to 33 billion barrels (bbl), both the largest volumetric and percentage increase in oil reserves since 1970, when 10 billion bbl of Alaskan oil reserves were added to the U.S. total. Proved oil reserves in 2012 increased for the fourth year in a row and were the highest since 1976.