Whiting Petroleum Corp. (NYSE: WLL ) closed the sale of its 50% interest in its Robinson Lake natural gas processing plant and associated natural gas gathering system in North Dakota, the company said Jan. 3. The plant and system are in Mountrail County, N.D. The sale of its 50% interest in its Belfield natural gas processing plant and associated natural gas, crude oil and water gathering systems in Stark, Billings and Dunn counties, N.D., also closed. The all-cash purchase price was $375 million, subject to closing and post-closing adjustments. Whiting Petroleum also said Jan. 3 that it will redeem all oustanding $275 million of 6.5% senior subordinated notes--due in 2018--on Feb. 2, 2017. The redemption will be funded through the midstream asset sale, the company said.