To an undisclosed buyer, Marathon Oil Corp. said it signed a deal to unload the majority of its assets in the Gulf of Mexico already in production.

Marathon said it was selling off its acreage in the Gulf of Mexico for $205 million.

"These assets represent a majority of the company's operated and non-operated producing properties in the Gulf of Mexico," Marathon said in a statement.

Onshore, the company reported mix production results from its U.S. operations. In North Dakota, the No. 2 oil producer in the country, the company reported a 22 percent increase in production from second quarter 2014 and a 7 percent gain from the previous quarter. In Texas, the No.1 producer, the company's net production was 32 percent higher than second quarter 2014, but 8 percent less than first quarter 2015.

The company last week reported a net loss for the third quarter of $749 million, with losses tied to lower crude oil prices and changes in its conventional exploration strategy.

Lee Tillman, the company's president and chief executive officer, said the strategy moving forward would be on "meaningful cost reductions" for the company. The slump in crude oil prices, which is forcing energy companies to re-examine their operations, is expected to endure, he said.

Marathon said it was holding on to some of its assets in the Gulf of Mexico, including the emerging Shenandoah basin. Last year, stakeholder Anadarko Petroleum said it encountered an oil layer measuring more than 1,000 feet thick while drilling into Shenandoah.

Marathon Oil holds a 10 percent working interest in that basin.