VANCOUVER (miningweekly.com) – Field production of crude oil in the US has risen to the highest level in four decades, reaching 9.42-million barrels a day in 2015, according to information provided by the US Energy Information Agency (EIA).

Output increased for the seventh consecutive year in 2015, the highest crude oil output level since 1972, based on final production numbers in EIA’s ‘Petroleum Supply Annual’.

In 2015, production gains were highest in Texas, the Gulf of Mexico, and North Dakota, as these three regions accounted for 77% of the US total increase, analyst Owen Comstock stated in the EIA’s ‘Today in Energy’ brief.

However, despite significant growth in output for 2015, monthly US crude oil output has declined since April 2015 on the back of collapsing oil prices. Lower West Texas Intermediate benchmark prices led to slower development activity, and output fell to 8.74-million barrels a day in August, the latest month for which survey data is available.

States or areas with the highest volumes of production also saw the largest gains in 2015, according to the EIA.

Texas is by far the largest crude oil-producing state, providing 3.46-million barrels a day in 2015, the highest level since at least 1981, when EIA’s state-level production series started. Texas output grew by 289 000 bbl/d in 2015, the largest increase of any state.

The federal offshore region of the Gulf of Mexico was second in both absolute level and 2015 increase, growing by 118 000 bbl/d to reach 1.52-million barrels a day, the highest production in that area since 2010. Output in North Dakota was third in both absolute level and 2015 increase, growing by 96 000 bbl/d to reach 1.18-million barrels a day, the highest on record for the state.

California production has generally declined since 1985 – when it was 1.08-million barrels a day – and averaged 550 000 bbl/d in 2015. Alaska’s crude oil output, almost all of which is in the North Slope, fell for the thirteenth consecutive year, declining to 480 000 bbl/d in 2015.