In a novel $525 million deal that is one of the first to be struck under Mexican energy industry reforms, two U.S. private-equity firms are teaming up to invest in an independent oil and gas exploration and production company in Mexico

EnCap Investments LP of New York and Riverstone Holdings LLC of Houston are each contributing $225 million, in combination with $75 million from the Mexican venture capital firm Infraestructura Institucional, to create Mexico City-based Sierra Oil & Gas S de RL de CV. All three companies have the right to double the dollar amount of their commitments once the initial equity is invested, according to a Sept. 18 news release.