US proved reserves of crude oil at yearend 2012 were estimated at 33.4 billion bbl, up 15.4% from 2011 and the highest since 1976, according to a report released Apr. 10 by the US Energy Information Administration.
The report, US Crude Oil & Natural Gas Proved Reserves (2012), outlined contributing factors to the higher reserves, including increased exploration for liquid hydrocarbons, improved technology for developing tight oil plays, and sustained high historical crude oil prices, EIA said.
The report said, in 2012, proved oil reserves increased in three of the top five largest crude oil and lease condensate areas, including Texas, the Gulf of Mexico federal offshore, and North Dakota. Texas recorded the largest volumetric increase of 3 billion bbl among individual states, largely because of development in the Permian and western gulf basins, while North Dakota had the second-largest increase (1.1 billion bbl), driven by development of the Bakken and Three Forks formations in the Williston basin.
Tight oil plays contain 7.3 billion bbl of proved crude oil reserves and lease condensate in 2012, accounting for 22% of the US total. Proved crude oil reserves in the Eagle Ford tight oil play in southwest Texas surpassed those in the Bakken formation of North Dakota to become the largest tight oil play in the US.
US wet natural gas proved reserves were 322.7 tcf at the end of 2012, down 26 tcf from the previous year.
Low natural gas prices, reflected in a 34% decline in the 12-month, first-of-the-month, average spot price of natural gas at the Henry Hub between 2011 and 2012, led to large negative net revisions (-45.6 tcf) to the reserves of existing fields that offset almost all gains from extensions of existing fields, EIA noted in its report.
However, the report anticipates that proved gas reserves for 2013 will be affected positively by the recovery in gas prices from 2012 to 2013.
Proved natural gas reserves in the Marcellus shale gas play in Pennsylvania and West Virginia surpassed those in the Barnett shale play of Texas to become the largest shale gas play in the US, EIA said.