Associated Press: The massive oil spill in the Gulf of Mexico will significantly set back industry efforts to increase offshore drilling, the CEOs of two Oklahoma City-based independent energy companies said Friday. Devon Energy Corp. CEO Larry Nichols and Chesapeake Energy Corp. CEO Aubrey McClendon spoke during an annual Oklahoma State University energy conference, with OSU President Burns Hargis asking questions submitted by audience members. The first question was about the April 20 …