Sinopec Group, China's biggest oil refiner by volume, said Thursday it has completed a deal to buy a 30-percent stake in the Brazilian assets of Galp Energia, a Portuguese energy company, at a cost of 5.16 billion U.S. dollars.

The completion of the acquisition will further expand Sinopec's overseas oil and gas business and give the company an additional daily output of 21,300 barrels of oil equivalent (BOE) by 2015 and 112,500 BOE per day in 2024, according to Sinopec.

Sinopec International Exploration and Production Corp., a wholly-owned auxiliary of Sinopec Group, took the latest shares released by Galp and covered the company's shareholder loans.

Galp, Portugal's largest oil association that binds stakes in 33 blocks of oil margin in Brazil, started a bidding process earlier last year, as it was looking for a partner to help finance its Brazilian projects.

Sinopec will also have board seats and representation in the company as part of the deal.