ConocoPhillips has agreed to buy Marathon Oil for $22.5 billion, as consolidation in the U.S. energy sector shows little sign of slowing down. internal-storyline-no, Mergers, Acquisitions and Divestitures, Oil (Petroleum) and Gasoline, Chevron Corporation, ConocoPhillips, Marathon Oil Corporation, Hess Corporation, Endeavor Energy Resources LP, Devon Energy Corporation, Institutional Shareholder Services Inc, Pioneer Natural Resources Company, Guyana, Houston (Tex) ConocoPhillips has agreed to buy Marathon Oil for $22.5 billion, as consolidation in the U.S. energy sector shows little sign of slowing down. NYT > Business