PetroChina in the third week of December 2012 agreed to buy a 49.9 percent stake in Canadian firm Encana's natural gas project in Alberta for 2.2 billion dollars. The project contains supplies equivalent to nearly nine billion barrels of oil. It is considered the latest investment in an overseas oil and gas resource by a Chinese firm. PetroChina, is China's biggest oil and gas producer.

Moreover, PetroChina announced it would buy BHP Billiton's stake in an Australian liquefied natural gas project. Significantly, another Chinese firm, CNOOC, got approval from Canadian government in December 2012 to take over oil firm Nexen.

The CNOOC-Nexen deal valued at15.1billion dollars, was China's largest overseas takeover. It shows the increasing Chinese influence on the Canadian oil and gas industry.