Reserves of oil and natural gas in the US were higher in 2014, according to the US Energy Information Administration (EIA), thanks, in part, to shale drilling, which has transformed the energy market.
EIA data showed that proved reserves of natural gas rose by 34.8 trillion cubic feet (tcf), or 10%, to a record high of 388.8 tcf in 2014, while oil reserves rose 3.4 billion barrels, or 9%, to 39.9 billion barrels, the highest since 1972.
The increases were driven by prolific production from shale plays that, through hydraulic fracturing, have produced vast amounts of fuel, creating a market glut and causing steep price drops. The price of oil has fallen more than 50% since last summer and natural gas prices have been depressed for years, both due to oversupply.
The Marcellus shale play in Pennsylvania, which produces 20% of the country's natural gas, contributed most to the increase in gas reserves, adding 10 tcf of proved reserves. The Texas portions of the Eagle Ford shale play and the Permian Basin saw the largest increase in oil reserves, adding 2.05 billion barrels. North Dakota saw the second largest increase, a gain of 362 million barrels, driven by the Bakken shale play.
Production of oil and natural gas increased in 2014, the EIA said. Production of crude oil and lease condensate increased about 17%, from 7.4 to 8.7 million barrels per day. Gas output increased 6%, from 73 to 77 billion cubic feet per day.