Marathon Oil selling UK offshore assets 13 December 2013 Last updated at 09:18 Marathon Oil is putting its UK offshore assets up for sale, it has been announced. Marathon operates the Brae complex, and also has stakes in the East Brae and Braemar fields as well in the Foinaven project west of Shetland. The company's UK operations are based in Aberdeen. Marathon is putting more resources into its shale gas projects in the United States.