Tullow, which will now be the sole owner of all the major oil fields in Uganda, had said earlier that it would immediately sell half of the stake either to Cnooc or Total of France in order to develop the oil fields if it gets Heritage's stake.

Since the discovery of field in 2007, six wells have been drilled in Blocks 1 and 3A by Tullow and Heritage and appraisal wells confirmed that fields hold approximately 1 billion barrels of oil.

But due to high cost involved in developing the fields and the related infrastructure, Heritage had put its stake for sale this summer.

The project required huge investments to build a 1,200 kilometre pipeline to the Kenyan port of Mombassa to export the oil as well as building a refinery.

For CNOOC, which has assigned a capital and exploratory budget of $7.93 billion for 2010 and having access to almost unlimited funding arranged by its financing subsidiary, has secured huge reserves, which will keep China's economy rolling after Beijing had given the green signal last year to its state-owned oil and mining companies to secure assets abroad, especially in Australia and Africa.