Exxon may try to upend its rival’s megadeal. The prize is a 30 percent stake in the oil-rich fields off the coast of Guyana.

​Read More Oil (Petroleum) and Gasoline, Guyana, Exxon Mobil Corp, Chevron Corporation, Hess Corporation, Mergers, Acquisitions and Divestitures, Developing Countries, Natural Gas, Territorial Disputes, CNOOC Ltd, Venezuela, Stabroek block