China Petroleum & Chemical Corp (Sinopec), the country's largest refiner, and CNOOC Ltd have agreed to buy a 20 percent stake in Angola's offshore deepwater Block 32 for $1.3 billion from Marathon Oil Corp.

Marathon, the fourth-largest US oil company, will keep a 10 percent interest in the block, site of 12 announced petroleum discoveries, after the sale, which is expected to close by the end of the year, the companies said Friday in separate statements.

Marathon said its partners in the block have the right to acquire the stake by matching the joint offer by CNOOC and Sinopec.

Total SA operates the block and holds a 30 percent interest. Angola's state-owned Sonangol SA has 20 percent, a unit of Exxon Mobil Corp owns 15 percent, and state-owned Petroleos de Portugal owns 5 percent, Marathon said.

It would be the fourth and largest divestiture this year of an exploration and production stake by Marathon, after it announced in March 2008 plans to sell at least $2 billion of assets.

Marathon in June agreed to sell its stake in an offshore Ireland natural-gas project to Vermillion Energy Trust for at least $235 million and completed the sale of US oil and gas fields for $181.1 million to Apache Corp. It sold its Irish unit to Petroliam Nasional Berhad, or Petronas, Malaysia's state-owned oil company, for $180 million in April.

Standard Chartered Bank advised Marathon on the Angola block sale. Credit Suisse Group AG advised CNOOC and Sinopec.

CNOOC shares rose 1.7 percent to HK$9.78 in Hong Kong on Friday. Sinopec gained 1.3 percent to HK$6.34.

Bloomberg News

(HK Edition 07/18/2009 page2)