Lin Boqiang, a researcher at the Xiamen-based China Center for Energy Economic Research, said the purchase will make up for CNOOC's weakness in onshore explorations and enhance its oil sands and shale gas operations.
As China's largest offshore oil producer, CNOOC operates mainly in seas off China but has assets in Asia, Africa, North America, South America and Oceania, 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.
The acquisition of Nexen needs further approvals by other governments involved, including the United States, but even a U.S. rejection, which looks unlikely to happen, will not affect the completion of the overall deal, Wang said.
CNOOC failed to win U.S. lawmakers' support for its 18.5 billion-U.S. dollar bid to buy U.S. oil producer Unocal over national security concerns in 2005.
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