BISMARCK-Marathon Petroleum Corp. announced Monday, April 30, it is merging with Andeavor, the owner of North Dakota's two oil refineries.

Marathon Petroleum is buying Andeavor for more than $23 billion, a transaction that would make the combined company the largest U.S. refiner.

The combined company will have headquarters in Findlay, Ohio, and will be called Marathon Petroleum, said Andeavor spokeswoman Destin Singleton.

Andeavor, recently known as Tesoro, employs 300 people at the Mandan Refinery and the Dickinson Refinery.

The Mandan Refinery has a capacity of 74,000 barrels per day, while the refinery four miles west of Dickinson has a capacity of 20,000 barrels per day.

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Andeavor also owns pipelines in North Dakota natural gas processing plants near Belfield and New Town and a rail terminal at Fryburg.

Marathon Petroleum owns an interest in the Dakota Access Pipeline.

Gary Heminger, Marathon Petroleum's chairman and CEO, said in a statement the transaction "combines two strong, complementary companies to create a leading U.S. refining, marketing and midstream company."

The merger is expected to close in the second half of 2018. Until then, Andeavor and Marathon Petroleum will continue to operate as separate companies.

After the transaction closes, Greg Goff, Andeavor chairman and CEO, will join Marathon Petroleum as executive vice chairman.

The Mandan Refinery was in the national spotlight in September when it hosted President Donald Trump for a speech on tax reform. The name change to Andeavor was still fresh at the time, with workers updating a Tesoro billboard with the new company name and logo the day before Trump's visit.

Andeavor Logistics has a pipeline project proposed before the North Dakota Public Service Commission that would transport natural gas liquids from the core of the Bakken to the Fryburg rail terminal. The project involves construction of three pipeline segments that total 44 miles and the conversion of 42 miles of the Andeavor BakkenLink crude oil pipeline into natural gas liquids service.

The Public Service Commission announced Monday a public hearing on the natural gas liquids proposal is set for 9 a.m. Mountain time on May 14 at Grassy Butte Community Hall. For more information on the proposal, visit