Exxon Mobil has lost its arbitration challenge to block Chevron's $55 billion Hess acquisition deal, but the top U.S. oil producer managed to delay the tie-up by over a year, costing its rival billions in lost Guyana oil revenue and slowing integration.

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 biggest oil discovery in decades - the Stabroek Block off the coast of Guyana,