China's state-owned energy colossus, CNOOC, has unveiled a $US15.1 billion ($A14.62 billion) bid to buy Canada's Nexen, in what would be the largest ever foreign commercial purchase by the oil-hungry nation.
Seven years after political panic about China's thirst for global energy assets scuppered a massive bid to take over California's Unocal, CNOOC said on Monday it was trying for another blockbuster North American deal.
The proposed CNOOC-Nexen takeover, which has yet to be approved by regulators, would be China's largest ever foreign investment and its largest ever energy deal, according to data firm Dealogic.
Calgary-based Nexen produces the equivalent of around 213,000 barrels of oil a day, with concessions in Canada's oil sands, Britain's North Sea, Nigeria, the Gulf of Mexico and Colombia.
China is the biggest energy consumer in the world, the second biggest consumer of oil and has been snapping up resource assets across the globe to fuel breakneck growth.
While Nexen has debts of about $US4.3 billion, the deal is likely to face scrutiny from regulators across a range of countries due to the Chinese government's involvement.
In Britain - where a large slice of Nexen's production takes place - the Office of Fair Trading said it was too early to comment.
In a joint statement, the firms tried to head off more likely concerns.
They pledged to keep the regional headquarters in Calgary and proposed Nexen take management of existing CNOOC operations in North America and the Caribbean.
Nexen's assets in Britain, the United States and other countries would continue to be managed from regional offices, and CNOOC would retain the current management, employees and local suppliers in those operations.
"CNOOC is already attempting to allay the inevitable concerns about regulatory roadblocks to the deal," said Barclays Capital analyst Harry Mateer.
"The company's plan ... should be viewed favourably by Canadian politicians, in our view."
The deal offers Nexen shareholders $US27.50 per share in cash, a premium of 61 per cent on Friday's closing price.
The deal is slated to close in the fourth quarter of this year.
If completed, it would be the biggest but by no means the only CNOOC investment in Canada.
CNOOC already has stakes in MEG Energy and oil sands producer OPTI Canada.
The OPTI project is a joint venture with US energy giant ConocoPhillips.