Chinese energy giant CNOOC has filed its formal application for Canadian government approval of its $15 billion offer for Canadian oil and gas producer Nexen Inc.

Canadian Industry Minister Christian Paradis said Wednesday he is conducting a review of the proposed acquisition announced last month by the Chinese state-owned company.

The foreign takeover requires government approval. Canada’s Conservative government rejected Anglo-Australian BHP Billiton’s hostile takeover bid for Saskatchewan’s Potash Corp. in 2010, but the government has allowed Chinese companies to take stakes in energy companies recently.

Calgary, Alberta-based Nexen operates in western Canada, the Gulf of Mexico, North Sea, Africa and the Middle East, with its biggest reserves in Canadian oil sands.

The government suggested this week it would like Canadian firms to get better access to the Chinese market.