Chevron closed its $55 billion acquisition of Hess on Friday after winning a landmark legal battle against larger rival Exxon Mobil to gain access to the largest oil discovery in decades.

Chevron Corp. has prevailed in a 20-month fight to buy Hess Corp. for $53 billion, overcoming a challenge by arch rival Exxon Mobil Corp. that was unprecedented in the modern history of Big Oil.

Arbitrators cleared the way for the long-delayed $53 billion acquisition after Exxon tried to pre-empt the deal.