PetroChina Co Ltd, Asia's biggest oil producer, will partner with Canadian company Encana Corp to develop a shale gas project in Alberta, in another major investment by a Chinese company in Canada.

Less than a week after CNOOC Ltd's $15.1 billion purchase of energy producer Nexen Inc was approved by Ottawa, natural gas giant Encana said on Thursday that PetroChina will pay C$2.18 billion ($2.14 billion) for a non-controlling 49.9 percent stake in Encana's Duvernay field, a promising shale gas formation in Alberta, which also has other resources.

"Shale gas development needs a large amount of capital investment, which makes it a good time to invest in an energy field in Canada. That country is working hard to develop its energy exploration to boost the economy," said Wang Ruiqi, an analyst at energy information consultancy ICIS C1 Energy.

The Chinese company's investment enables Encana to accelerate the pace at which the full production potential of the Duvernay field can be achieved, said Randy Eresman, president and chief executive officer of Encana.

The companies said that C$1 billion will be paid over the next four years to help Encana pay for the development costs of the project, which the Canadian company estimates to have reserves of about 9 billion barrels of oil equivalent petroleum. During this period, the joint venture partners will invest a total of C$4 billion in new drilling and processing facilities.

Encana expects to more than double its planned pace of development in the Duvernay field in early 2013.

Earlier this week, PetroChina bought the mining giant BHP Billiton Ltd's stake in a liquefied natural gas project in Australia for $1.63 billion. The deal is expected to be completed in the first half of next year.

PetroChina is boosting its acquisitions overseas to meet the increasing domestic demand for natural gas, Wang said.

"However, neither of the two agreements involving PetroChina announced this week mentioned the productionsharing details, which makes the two projects' exact contribution to China's energy supply unclear," Wang added.

As the country's energy consumption grows rapidly, Chinese companies are expected to accelerate their gas-related acquisitions overseas to own more exploration rights and reserves.

"Chinese and foreign oil and gas giants are investing more in the gas sector than in the oil sector because gas is profitable and environmentally friendly," said Wang.

The Chinese natural gas market has huge potential, said Peter Voser, Shell's chief executive officer, during an earlier interview with China Daily.

Wang Hui, an analyst at chem365.net, an online information provider for the petrochemical industry, said: "As an energy company with most of its assets in Asia, PetroChina has to look for more assets in other parts of the world to become diversified."