Oil production from key shale formations in North Dakota and Texas increased slightly in July from June, according to a report by Bentek Energy, an analytics and forecasting unit of Platts.

Bentek said Aug. 21 oil production from the Eagle Ford Basin in Texas remained relatively strong in July, up 10,000 barrels per day (bbl/d), but less than 1%, from June. This increase followed the growth trend that has been set by the basin since January of this year when oil production showed the first and so far only sign of decline when it decreased 14,000 bbl/d month-on-month.

Crude oil production in the North Dakota section of the Bakken shale formation of the Williston Basin remained flat, increasing less than 500 bbl/d, or less than 1% in July vs. June.

The average oil production from the Eagle Ford Basin last month was 1.6 MMbbl/d. On a year-over-year basis, that is up a little less than than the incremental 250,000 bbl/d, or about 17% higher than July 2014, said Sami Yahya, Bentek energy analyst, in the report. The average crude oil production from the North Dakota section of the Bakken formation in July was 1.2 MMbbl/d, or up about 90,000 bbl/d from year-ago levels.

"It is the flight to quality and higher returns that is keeping crude production going in those two key shale basins," Yahya said. "Initial production (IP) rates have been improving, especially in the oily window of the Eagle Ford Basin. As well, producers in the Eagle Ford are currently drilling 2.5 wells per rig per month, which is higher than the national average of 1.5 wells. Drill times have been improved from an average of 15 days per well in 2014 to roughly 11 days per well in 2015."

The Bakken shale formation follows closely behind the Eagle Ford Basin in terms of efficiency gains and internal rates of return, Yahya added. Drill times in this basin have dropped from about 15 days per well in late 2014 to about 13 days per well during the second quarter of this year, he said.

"Substantial cost savings protocols alongside reduced drill times have kept internal rates of return (IRR) in the Bakken shale formation among the best in the country," Yahya said. "Current rates of return in the Bakken shale formation are around 15%, which is comparable to the 18% found in the Eagle Ford Basin."

Bentek analysis shows that from July 2014 to July 2015, total U.S. crude oil production has increased by about 550,000 bbl/d.