TORONTO (AP) — A subsidiary of China’s state-owned PetroChina and Canada’s Encana Corp. have entered into a multibillion dollar joint venture agreement to explore and develop shale natural gas in Alberta, the Canadian oil and gas company said Thursday.

Encana said the PetroChina subsidiary, Phoenix Duvernay Gas, will invest $2.21 billion for a 49.9 percent interest in about 445,000 acres (180,000 hectares) Encana has in the emerging Duvernay formation.