Chinese oil conglomerate China National Offshore Oil Corp. (CNOOC) Ltd. is preparing to move ahead with the country's biggest ever overseas acquisition.

On December 8, the Canadian Government approved CNOOC's $15.1 billion bid to buy Calgary-based oil and gas producer Nexen Inc., paving the way for the final completion of the long-debated deal.

The takeover boosts CNOOC's international ambitions and diversifies its business but also contains political and financial risks, experts said.

CNOOC said acquiring Nexen's assets will strengthen its presence in Canada, Nigeria and the Gulf of Mexico and allow it to enter the oil- and gas-rich North Sea regions.

As China's largest offshore oil producer, CNOOC operates mainly outside China and has assets throughout the world, according to company information.

Nexen runs oil sands and shale gas projects in western Canada and conducts conventional explorations primarily in the British North Sea, offshore West Africa and the Gulf of Mexico.