Two shale counties in Texas dominated the landscape, though crude oil production is holding relatively stable, data from the state show.

The Railroad Commission of Texas, the state energy regulator, reported preliminary production of crude oil averaged 2.38 million barrels per day in September, less than 1 percent lower than the previous month and 1.6 percent lower than for September 2015.

Texas is the No. 1 oil producer in the United States and, over the past 12 months, produced 995 million barrels of crude oil. A recent survey, meanwhile, from the U.S. Geological Survey found the Wolfcamp shale reserve within the Permian basin in Texas could be the largest oil and gas deposit ever assessed in the country.

State data show Midland County, which hosts part of the Wolfcamp, produced 5.06 million barrels of oil for the whole month of September. Karnes County, which hosts parts of the Eagle Ford shale, produced 5.09 million barrels of oil in September.

The entire Permian basin, which includes Wolfcamp, holds nearly as many active oil rigs as the rest of the United States combined. The federal Energy Information Administration reported that, as crude oil prices recover and spending starts to move back into the U.S. energy sector, a full-scale rebound is possible for inland resources.

Crude oil prices have recovered to the upper $40 per barrel range, after sinking below $30 per barrel in early 2016. Based on prices at the start of November, the price for West Texas Intermediate crude oil, the U.S. benchmark, is up 1.1 percent, or 54 cents per barrel from last year.

The Federal Reserve Bank of Dallas said last month that, despite a period of historically lower crude oil prices, there were broad indicators of recovery in the Texas economy. Addressing the bank in mid November, Jim Diffley, a senior director at consultant group IHS, said the energy sector in oil-rich states like Texas likely bottomed out, but it will be a long road to recovery.