Private equity (PE) upstream investor Ridgewood Energy Corp. is partnering with a fund managed by Riverstone Holdings LLC to invest more than $550 million in a series of deepwater exploration projects in the Gulf of Mexico (GOM).

Ridgewood would oversee the investments on behalf of the venture. Combined with a similar commitment by an affiliate of Riverstone/Carlyle Global Energy and Power Fund IV LP in 2010, this brings the total Riverstone-sponsored fund commitment to the venture to more than $550 million.

The PE firms formed the GOM venture in 2010 and since then have participated in four discoveries in the Mississippi Canyon and Ewing Bank blocks of the deepwater GOM. The four discoveries all are being developed, with projected start-up dates in 2015 and early 2016.

Riverstone and Ridgewood have another seven exploration “opportunities” in the works, the first of which is to begin drilling this month.

Riverstone, which has more than $24 billion of PE capital across seven investment funds, targets all energy sectors, including exploration and production (E&P), midstream, oilfield services, power and renewables.

Last year, Riverstone and PE firm Apollo Global Management launched Talos Energy LLC, a Gulf Coast-focused E&P that operates primarily in shallow water (see Daily GPI, April 5, 2012). Riverstone also helped to launch GOM explorer Phoenix Exploration Co. in 2006; the company later was bought by Apache Corp. (see Daily GPI, April 21, 2006). In 2005 it partnered to fund the launch of deepwater explorer Cobalt International Energy Inc. (see Daily GPI, Dec. 2, 2005).

Ridgewood Energy Funds’ forte is the GOM, where it has a stake in 29 oil and gas discoveries in the shallow and deepwater. In addition, the funds own interests in 70 federal and state lease blocks in the GOM, totaling more than 475 square miles.

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