Houston, Texas – April 22, 2009: Cobalt International Energy, L.P. and Sonangol, E.P. today jointly announced the formation of a major partnership in the deepwater Gulf of Mexico and the deepwater offshore Angola.

Cobalt will assign 25% of its working interest in 11 Gulf of Mexico deepwater leases to the U.S. subsidiary of Sonangol P&P, Sonangol Exploration and Production International Ltd. Additionally, Cobalt and Sonangol have agreed to a Joint Participation Area in the Gulf of Mexico for any future joint venture opportunities between the parties. Cobalt will remain operator of these blocks on behalf of the partnership.

Sonangol, E.P also announced that Cobalt will be assigned a 40% working interest in the consortium for Blocks 9 and 21 offshore Angola. Cobalt will be designated as operator of the consortium for the two deepwater offshore blocks. Additionally, Sonangol and Cobalt have agreed to consider other joint participation opportunities between the parties offshore Angola.

Cobalt and Sonangol anticipate drilling to begin on the jointly held Gulf of Mexico leases as early as this summer. Drilling in Angola is anticipated in 2010.

Since its inception in 2005, Cobalt has established a highly prospective and substantial exploration portfolio in the deepwater Gulf of Mexico. In addition, Cobalt has had a focused exploration effort on highly prospective basins in deepwater West Africa

"We are extremely pleased to partner with Sonangol in their entry into the deepwater Gulf of Mexico and Cobalt’s entry into the deepwater offshore Angola" said Joseph H. Bryant, Cobalt’s Chairman and Chief Executive Officer. "The strength of such a partnership is clear. Our combined expertise and experience in both of these highly prospective basins will yield tremendous results. We look forward to deepening and broadening our relationship with Sonangol in the future".

As Angola’s national oil company, Sonangol continues to grow the country’s production profile at a significant pace. By the end of 2008, Angola achieved an annual production target of close to 2 million barrels per day. Sonangol continues to pursue its objective to diversify and internationalize the company wherever it is viable to do so.

"Sonangol’s entry into the Gulf of Mexico is a significant milestone in our growth as a global enterprise. To be able to partner with a company of Cobalt’s reputation is an extraordinary opportunity for us" said Manuel Vicente, Sonangol’s Chairman and Chief Executive Officer.

"Through this partnership, we look forward to developing first hand knowledge of the Gulf of Mexico, which is one of the world’s most prospective basins, utilizing state-of-the art exploration and development technology. At the same time, the partnership looks forward to exploring additional deepwater potential offshore Angola".

Questions regarding Cobalt should be directed to:

Richard Smith: +1 713 579 9141

Questions regarding Sonangol should be directed to:

Carlos Saturnino, Negotiations Director: + 244 226 642 776; + 244 226 642 777

: Fax: + 244 226 642 926

About Cobalt:

Cobalt International Energy, L.P. is a private oil and gas exploration and production company focusing on the deepwater of the Gulf of Mexico and West Africa. The company was formed in 2005 and is headquartered in Houston, Texas. Cobalt currently now holds a working interest in 221 leases in the Gulf of Mexico deepwater, Blocks 9 and 21 offshore Angola, and in the Diaba License offshore Gabon. Cobalt’s financial sponsors include Goldman Sachs, Carlyle/Riverstone, First Reserve Corporation, KERN Partners, and Management.

For more information on Cobalt, please visit their website at www.cobaltintl.com.

About Sonangol:

Created in 1976 through the nationalization of ANGOL, Sonangol’s breadth of activities include prospecting, research, development, sales, production, transportation and the refining of Angola’s hydrocarbons and their derivatives. In this context, Sonangol is continues to diversify and internationalize both in African and international markets where viable to do so.

For more information on Sonangol, please visit their website at www.sonangol.co.ao.

Gulf of Mexico: Cobalt-Sonangol AMI

Angola Blocks 9 and 21