OXY USA submitted an application with the North Dakota Industrial Commission in September seeking approval to drill up to seven horizontal wells in each of seven contiguous 1,280-acre standup spacing units in the Crooked Creek field in western Dunn County. Three of the wells on each unit will target the Pronghorn formation. OXY indicated in April that it was planning to test the Pronghorn formation.
Of the other four wells on each unit, three will target the middle Bakken and the fourth will target the Three Forks. That configuration in seven spacing units will result in a total of 21 Pronghorn wells, 21 middle Bakken wells and seven Three Forks wells in the development. OXY reports an estimated ultimate recovery, based on middle Bakken data, of 319,000 barrels of oil per well.
Farther west, Whiting Oil and Gas submitted an application seeking approval to drill four horizontal wells targeting the Pronghorn and upper Three Forks on a 1,280-acre standup unit in the Ash Coulee field in western Billings County. Whiting reports an EUR of 230,000 barrels per single lateral well.
The Ash Coulee spacing unit is part of Whiting’s Lewis and Clark prospect, which is adjacent to its Pronghorn prospect where the company has been producing from the Pronghorn formation since 2012. Whiting announced as late as Sept. 30 that two of its Pronghorn wells in the Lewis and Clark prospect came in with 24-hour initial production rates of 1,098 and 1,348 barrels of oil equivalent per day. Whiting also announced that it plans to test increasing Pronghorn well densities from three to six wells per 1,280-acre spacing unit.
The Pronghorn is a limestone/mudstone unit that lies between the lower Bakken Shale and the upper Three Forks in parts of Stark, Dunn, McKenzie, Billings and Golden Valley counties in west-central North Dakota. As Petroleum News Bakken reported in November 2012, segments of the Pronghorn had been seen in cores for years, but it was considered part of the Three Forks formation and was commonly known as the Sanish member. It wasn’t until Anschutz Petroleum cut a core while drilling its 24-14H Sadowsky well in 2009 that completely transcended the unit that the Pronghorn was formally defined. That well, which is now operated by OXY, is in the St. Anthony field south of the Crooked Creek field in the southwest corner of Dunn County. The Pronghorn formation in that core is approximately 43 feet thick.
Julie LeFever, director of the North Dakota Geological Survey’s core library, said the reason the formation was named “Pronghorn” was that the term “Sanish” became a regulatory term for both oil and gas fields and pools in North Dakota. The term “Pronghorn” was intended to avoid confusion.
