Guardian: The mature fields, called Magnolia, Merganser, Nansen and Zia, currently produce 15,000 barrels of oil a day for BP BP has raised $650m (£413m) by selling four oil fields in the Gulf of Mexico, the latest in a series of asset sales following the Deepwater Horizon disaster. The oil giant announced this morning that Marubeni Oil and Gas, a Japanese company, has agreed to buy the four sites. The deal comes just seven months after BP acquired them as part of a wider $7bn deal with …