The government of Canada has approved the long-gestating takeover of oil and gas firm Nexen (UNKNOWN:NXY.DL) by China National Offshore Oil Corporation (CNOOC (NYSE:CEO)). Prime Minister Stephen Harper announced the news in a press conference. The buyout will total CA$15.1 billion ($11.7 billion), and had been approved by Nexen's shareholders in a vote this past September.

During the press conference, Harper also unveiled new guidelines for evaluating potential buyouts of Canadian companies by state-owned enterprises such as CNOOC. In the Chinese firm's bid for Nexen, concerns had been raised about the potential influence of foreign governments over the country's strategic assets.

Nexen was founded in 1969 as Canadian Occidental Petroleum, the country's branch of Occidental Petroleum (NYSE:OXY).  It netted a profit of CA$697 million ($539 million) in 2011, on revenue of CA$6.4 billion ($4.9 billion).

Separately, it was announced during the press conference that the Canadian government also approved a CA$5.2 billion ($4.0 billion) buyout of Progress Energy Resources by a subsidiary of Malaysia's state-owned Petronas.