Nearly half of the crude oil produced in the Lower 48 states last year came from wells drilled since the start of 2014, federal officials said Tuesday.

The U.S. Energy Information Administration (EIA) reported that domestic oil output from wells that were drilled in 2014 made up 48% of Lower 48 production in 2015. That compares with 22% of output in 2007.

“Production from new wells has grown as advances in horizontal drilling and completion techniques led to growth in oil production from low-permeability tight reservoirs,” EIA said.

Last year, tight formations, including shale, accounted for more than 4 million b/d of oil production, or 50% of total U.S. output, researchers said.

“U.S. oil production from tight formations increased from 0.5 million b/d in 2009 to 4.6 million b/d in May 2015, at which point decreasing oil prices contributed to declines in oil production,” according to EIA.

As of last December, oil production from tight formations was 8% lower than in May 2015. More than 80% of oil production from tight formations originated from the Eagle Ford and Bakken shales, as well as the Permian Basin.

“Horizontal wells drilled into tight formations tend to have very high initial production rates, but they also have steep initial decline rates,” EIA said. “With steep decline rates, constant drilling and development of new wells is necessary to maintain or increase production levels.”

EIA in 2013 began issuing monthly Drilling Productivity Reports (DPR), which track rig counts and the output from newly drilled wells, key indicators of future production. The March DPR issued earlier this month said April likely would be another in a series of sluggish months for oil and natural gas production in the nation’s seven largest unconventional plays (see Shale Daily, March 7).

Future production may be affected not only by the rig count and output, but by drilled but uncompleted wells, aka DUCs, as well as recompletions/refractures of existing wells, EIA said.

“Oil production from new wells has so far been able to keep U.S. crude oil production from falling significantly below its level in late 2014,” EIA said. “However, EIA’s Short-Term Energy Outlook projects that U.S. oil production will decline over the next two years, falling to 8.7 million b/d in 2016 and to 8.2 million b/d in 2017” (see Shale Daily, March 9).