CNOOC Ltd, China's biggest offshore oil producer, said today it has completed the US$15.1 billion acquisition of Canada's Nexen Inc.

This comes seven months after the deal, China's largest overseas takeover, was first announced, with regulatory approvals from both Canada and the United States where Nexen also has exploration and production assets in the Gulf of Mexico.

Nexen will operate as a wholly-owned subsidiary of CNOOC and will continue to be led by its CEO, Kevin Reinhart, who has been with Nexen for over 18 years.

CNOOC Chief Executive Li Fanrong will be the chairman of Nexen.

Calgary-based Nexen will be delisted.