Oil production from inland shale basins in the United States is expected to be more robust than previously thought, OPEC said in its global outlook.

The Organization of Petroleum Exporting Countries released its much-watched World Oil Outlook report for 2015, outlining its expectations for the global energy sector. OPEC has defended its market share during the past year as higher U.S. oil production pushed sector dynamics heavily toward the supply side. Coupled with weak global economic growth, crude oil prices have plummeted from above the $100 per barrel mark in mid 2014 to below $40 per barrel.

In its latest outlook, OPEC said it expects U.S. crude oil production from shale deposits to increase from 3.8 million barrels per day in 2014 to 4.9 million bpd by 2023. By 2040, the trend will start to reverse as U.S. shale output falls to 4.2 million bpd.

"Although the updated forecast for the 2015 outlook shows that U.S. tight crude [oil production] will decline gradually over the long-term to 4.2 million bpd in 2040, in the 2014 outlook, it was projected at only 2.8 million bpd in 2040," the report said.

From the U.S. perspective, a drilling productivity report from the U.S. Energy Information Administration found that, of the seven inland shale basins that accounted for domestic oil production growth, few are expected to report gains next year. Only the Permian shale basin that straddles the border of Texas and New Mexico and the Utica shale in the U.S. Midwest are expected to report increased in production from November.

A full-year 2014 profile from the EIA found total U.S. proved oil reserves of 39.9 billion barrels marked a 9 percent increase from the previous year. Total reserves for that year where their highest since 1972.