Some of the world’s best-known oil majors are expected to compete in a long-awaited auction for deepwater contracts in Mexico on Monday that marks a key opening of the country’s energy sector. ExxonMobil, BP, Royal Dutch Shell and Chevron and China’s Cnooc are set to be among bidders for blocks in the Gulf of Mexico that have been off-limits to private investment for nearly eight decades. ”It is the start of the big oil game” in Mexico, said Pablo Medina, analyst at Wood Mackenzie, an energy consultancy. The auctions will be the first big test of investment appetite in Mexico since Donald Trump romped to victory in the US election with populist pledges including renegotiating the North American Free Trade Agreement. His Nafta pledge could, if realised, bump up exploration costs in Mexico if imports of heavy equipment needed for drilling were subjected to tariffs