Proved crude oil reserve additions in the United States reached a record volumetric increase in 2011, the second year in a row that a record was set, the Energy Information Administration (EIA) said in its Today in Energy brief, which was released Thursday. The increase in crude oil reserves of 15 percent – or about 3.8 billion barrels – sent crude oil reserves to the highest level since 1985.
While not setting a record, proved natural gas reserves increased by nearly 10 percent – or about 31.2 trillion cubic feet (Tcf) – making it the second largest annual increase since 1977. Additions to reserves of natural gas might have been even larger, had a drop in natural gas prices not occurred, the EIA said.
The data for 2011 was the most recent year that complete data was available, an EIA spokesperson told Rigzone. Data for 2012 is still being collected.
“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,” the EIA explained.
The increases were driven by a combination of technology and producing formations.
“Horizontal drilling and hydraulic fracturing in shale and other tight rock formations continued to increase oil and natural gas reserves,” said Adam Sieminski, EIA administrator.
The rise in proved reserves began sometime in the mid-2000s, and coincides with the increased use of horizontal drilling and hydraulic fracturing technics in shale formations.
Proved oil reserves, including crude oil and lease condensate, were up by 29 billion barrels. That was the third consecutive yearly increase and the largest volume of proved reserves since 1985. Proved reserves in tight oil plays made up 3.6 billion barrels – 13 percent – of total proved reserves of crude oil and lease condensate in 2011, the EIA said.
The largest increase in proved oil reserves was in Texas, and was due mainly to the Eagle Ford formation in the Western Gulf Basin, and the Permian Basin shale formation. The second largest increase was in North Dakota, and was attributed to the Bakken formation in the Williston Basin.
The two states of Texas and Pennsylvania combined to add almost three-quarters, or 73 percent, of the net increase in p reserves in 2010, increased its reserves by 12.7 Tcf in 2011. That was about 41 percent of the overall gain in proved resources in 2011. Sales gas plays accounted for 131.6 Tcf –or about 38 percent – of total proved reserves of natural gas in 2011.
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