Houston offshore driller Energy XXI Gulf Coast agreed Monday to be bought by a privately held Dallas company, Cox Oil, for $322 million. Energy XXI emerged from bankruptcy more than a year ago, but continued to struggle financially. The new deal would cancel an agreement reached just a month ago for Virginia-based Orinoco Natural Resources to buy a 35 percent stake in Energy XXI. Energy XXI, which is focused in the Gulf of Mexico, was hard hit by the recent oil bust, and like many companies, filed for bankruptcy.