PetroChina will buy the remaining 40 percent stake in a Canadian oil sands project for $680 million.

Calgary's Athabasca Oil Sands Corp. sold a 60 percent share in its Mackay River project to PetroChina, China's largest oil company by market value, for $1.9 billion in 2009.

The deal for buying the balance of Mackay River, announced Tuesday by Athabasca, marks the first oil sands project to be fully owned by a Chinese company in the region, Athabasca said in a statement.

Last week Alberta regulators approved the 150,000 barrel-a-day Mackay River project, which is to begin at 35,000 barrels a day in 2014.

PetroChina's full ownership represents a good deal for both companies, says Athabasca President and Chief Executive Officer Sveinung Svarte.

"I think this is what you call a perfect divorce because PetroChina has ambitious growth plans for Canada and they're very happy to get these additional barrels, whereas we are pleased as well to take the proceeds and develop (Athabasca's) 100 percent assets faster," Svarte told the Calgary Herald.

Zhiming Li, president of PetroChina's Canadian subsidiary Cretaceous Oilsands Holding Ltd. said PetroChina has been working on the project for nearly two years.

While PetroChina is capable of developing the Mackay River project on its own, Li said, the company is "considering standards of how to select a partner."

And PetroChina is looking to make more deals beyond Athabasca, Li said.

"PetroChina is a very big company, looking for opportunities worldwide," he said, noting that oil sands "are a major target."

But Li stressed that PetroChina would only consider sizeable deals.

"It should not be just 35,000 barrels (per day). It should be bigger than that. Much bigger," he said.

The Athabasca deal is just the latest acquisition by a Chinese oil company as the country beefs up overseas investment in exploration and production in its quest to secure energy supplies.

Also Tuesday, China Petroleum and Chemical Corp, known as Sinopec, invested $2.2 billion to acquire an interest in U.S. company Devon Energy's shale fields.

Last year Sinopec bought Daylight Energy Ltd., a Canadian conventional-oil and natural-gas company for $2.2 billion and in 2010 paid $4.65 billion for a stake in Alberta's Syncrude oil sands project, The Wall Street Journal reports.

China's energy consumption per gross domestic product is double the world average, with more than half of the petroleum it consumes coming from imports, said Zhang Ping, director of the National Development and Reform Commission.