The Associated Press reports that PetroChina Ltd., China''s biggest oil and gas producer, has agreed to pay $5.4 billion for a 50-percent stake in Encana Corp''s shale natural gas play in northeastern British Columbia in what would be the largest-ever Chinese investment in Canada''s energy sector. Encana, Canada''s biggest natural gas provider, said the invesment from the state-owned Chinese firm will allow it to accelerate development of its Cutbank Ridge assets. PetroChina''s interest represents current daily production of 255 million cubic feet of gas per day, proved reserves of one trillion cubic feet of natural gas and nearly 635,050 acres of land. The transaction requires Canadian and Chinese government approval. Prime Minister Stephen Harper''s Conservative government blocked Anglo-Australian BHP Billiton''s outright takeover of Potash Corp. of Saskatchewan last November but Harper has allowed Chinese companies to take stakes in Canadian energy companies recently.