By ANDREW ROSS SORKIN, BRIAN O’KEEFE, BERNHARD WARNER, SARAH KESSLER, MICHAEL J. DE LA MERCED and NIKO GALLOGLY Exxon Mobil has a long history of drilling in challenging environments. The largest U.S. oil company will go almost anywhere to extract hydrocarbons if it can manage the risk and make the numbers work. Exxon pumps crude in the deep water off the coast of Guyana and has invested some $19 billion to produce natural gas on the island nation of Papua New Guinea. But at a highly staged...