Marathon Oil Corp. said Monday it is selling most of its operated and nonoperated properties in the Gulf of Mexico (GOM) to an undisclosed buyer for $205 million.

The assets include operated properties in the greater Ewing Bank area and nonoperated assets in the Petronius and Neptune fields. The buyer would assume all future abandonment obligations in the transaction, scheduled to close by the end of the year.

The Ewing Bank assets being sold include the Arnold (62.5%), Lobster and Oyster fields (66.67% each). The Ewing Bank development consists of a steel jacket structure and production facilities that were installed in 1994 in a water depth of 775 feet.

Marathon holds a 30% stake in Neptune, which is in Atwater Valley. Field development consists of subsea wells tied back to a mini-tension-leg platform (TLP). The mini-TLP is situated above the Sigsbee Escarpment on Green Canyon Block 613 in 4,300 feet of water. The subsea wells are below the escarpment in 6,200 feet of water.

In the Petronius field in Viosca Knoll, Marathon has a half-stake. The development consists of a compliant tower structure with production and drilling facilities that were installed in 1999 in water depths of 1,754 feet.

The Houston-based producer is retaining its stakes in some producing assets in the GOM, as well as interests in Gunflint and the Shenandoah discovery. Marathon holds an 18.23% working interest in Gunflint, which is in Mississippi Canyon (see Daily GPI, June 18, 2013). The Shenandoah prospect is in Walker Ridge; Marathon has a 10% stake (see Daily GPI, March 22, 2013). Gunflint is a subsea tie-back, with first production expected in 2016. Shenandoah’s first appraisal well reached total depth in 2013, with a second well spud last year. Another appraisal well is under way.

The company of late has focused more of its capital on U.S. onshore targets, including in the Eagle Ford and Bakken shales, and emerging Oklahoma plays (see Shale Daily, Nov. 6).