Riverstone Energy, the FTSE 250 energy investor that floated in London in October, has committed up to 82m dollars in a Gulf of Mexico oil and gas company set up by Riverstone's private equity parent. Riverstone is investing an intial $54m into exploration and production company Fieldwood Energy to help fund a recently agreed acquisition.The remaining unfunded commitment is being reserved for strategic bolt-on acquisitions.Fieldwood is the leading operator on the Gulf of Mexico shelf, a shallower section of the ocean basin, where in February it closed the acquisition of SandRidge Energy's Gulf unit, adding an additional 57m barrels of oil equivalent and production in excess of 25,000 barrels of oil equivalent per day.Pierre Lapeyre and David Leuschen, Co-Founders of Riverstone Energy's parent company Riverstone Holdings, said in a statement they believed the Gulf of Mexico shelf has been and will continue to be one of the most prolific oil and gas provinces in the world."Additionally, this investment provides immediate scale and diversification to Riverstone Energy's asset base, and demonstrates delivery of the strategy that we presented to investors at the time of the IPO."Following the SandRidge purchase, Fieldwood now has a leasehold of more than 650 blocks in the Gulf of Mexico.Pro forma for the two acquisitions, the Company generated over $1.7 billion of 2013 estimated earnings before interest, tax, depreciation and amortisation, implying modest leverage of approximately 2 times funded debt to EBITDA. Additionally, the company has significant undrawn debt capacity and equity commitments. Shares in Riverstone Energy were down 1.4% to 906.75p at 08:05 on Thursday.OH