Operators in the US replaced 164% of dry natural gas production and 122% of crude oil production in 2005, the US Energy Information Administration estimated.
US proved reserves at Dec. 31, 2005, were 21.757 billion bbl of crude oil, up 1.8% on the year, 204.385 tcf of gas, up 6.2%, and 8.165 billion bbl of natural gas liquids, up 3%.
The 11.87 tcf increase was the largest gain in natural gas proved reserves since 1970, but 2005 was the first uptick for oil reserves in 3 years, EIA said.
Oil production fell 4.7% to 1.733 billion bbl, gas output was down 4% to 18.458 tcf, and NGL production dropped 4.7% to 788 million bbl in 2005, the agency pointed out
As in most recent years, most of the oil and gas reserves additions in 2005 came from extensions to existing fields, not from new field or new reservoir discoveries.
Booked Gulf of Mexico deepwater reserves fell to 4.042 billion bbl of oil and 17.427 tcf of gas. Both figures include the Alabama federal offshore area.
Gas reserves
Gas reserves additions in the Lower 48 states alone overcame a 10% drop in gas reserves reported for the Gulf of Mexico federal offshore to 17.427 tcf, EIA said.
Texas and Colorado led the nation in 2005 gas reserves additions with notable reserves increases in Newark East field, core field of the Barnett shale play in the Fort Worth basin, and Ignacio-Blanco field, producing from tight sands and coal beds in the San Juan basin in southwestern Colorado.
Gulf gas production had been falling about 10%/year for several years before hurricanes Katrina and Rita in August and September 2005.
Extensions to existing gas fields in 2005 added 21 tcf, 16% more than in 2004 and 74% more than the prior 10-year average. New field gas discoveries were 942 bcf, 46% less than the prior 10-year average, and new reservoir gas discoveries in old fields were 1.2 tcf, 45% less than the prior 10-year average.
EIA figures for Wyoming showed 2 tcf of reserves added from field extensions, while upward revisions of 2.2 tcf more than made up for 1.8 tcf of negative revisions. This brought the state’s dry gas reserves to 23.8 tcf at the end of 2005.
US coalbed methane reserves climbed 8% to 19.892 tcf, and CBM production was up slightly to 1.732 tcf. Coalbed methane production was listed in Alabama, Arkansas, Colorado, Indiana, Kansas, Montana, New Mexico, Ohio, Oklahoma, Pennsylvania, Utah, Virginia, West Virginia, and Wyoming.
Exploratory and developmental gas completions were up 27% from 2004.
Oil and NGL
Oil reserves declined in Alaska and the Gulf of Mexico federal offshore and increased in Texas and California.
The oil reserves figures do not include volumes in large deepwater discoveries that have been made in recent years in the gulf and are not yet booked (OGJ, Sept. 25, 2006, p. 36).
Texas, Wyoming, and Montana were the top three states with Lower 48 oil reserves increases.
Extensions to existing oil fields in 2005 added 805 million bbl of reserves, 30% more than in 2004 and 53% more than the prior 10-year average. Most of the reserves increases from extensions came at fields in Texas, California, Montana, and Wyoming.
New field oil discoveries added 205 million bbl, almost totally (201 million bbl) in the gulf and six times the 2004 figure and only 49% of the prior 10-year average. New reservoir discoveries in existing fields were 41 million bbl, 69% less than 2004 and 23% of the prior 10-year average.
Oil production was lower in the gulf and in Alaska. Rocky Mountain states generally had gains, with Montana posting the largest increase of 36% to 427 million bbl from Bakken formation development in the Williston basin.
Exploratory and development oil completions were 25% higher than in 2004.
Operators replaced 130% of NGL reserves, the sum of lease condensate and natural gas plant liquids reserves. NGL reserves represented 27% of combined crude oil, condensate, and plant liquids reserves of 29.922 billion bbl.