Chevron said on Monday it agreed to buy Hess for $US53 billion ($84 billion) in stock, the second proposed megamerger among the biggest US oil players after ExxonMobil bid $US60 billion for Pioneer Natural Resources earlier this month.

The proposed deal raises the competition between Chevron, the No. 2 US oil and gas producer behind Exxon, and it will make it an unusual partner with its bigger rival in Guyana, as Hess, along with China’s CNOOC, were working together to develop drilling in the country.

Reuters