The $7.06-billion (5.33-billion-euro) sale, which British energy group BP expects to complete next year, will give Bridas total ownership of Pan American, the second largest producer of oil and gas in Argentina.
Bridas is owned 50 per cent by Cnooc International, the international arm of China National Offshore Oil Company, and 50 per cent by Bridas Energy Holdings, which is owned by Argentina's Bulgheroni family.
In a statement, BP said the deal was part of its plan to divest up to $30 billion of assets by the end of 2011 to cover costs incurred during the devastating oil spill at a BP rig in the United States earlier this year.
It has so far raised $14 billion from asset sales, before the Pan American deal.
BP group chief executive Bob Dudley said: "Today's agreement further demonstrates both the high quality and attractiveness of the assets throughout BP's global portfolio and also the company's ability to meet our significant financial commitments arising from the Gulf of Mexico tragedy.
"We now have agreements in place that should secure the majority of our divestment target.
"We will continue to identify further assets that may be strategically more valuable to others than to BP as we complete the programme."