Husky Energy, a Canadian company, and its Chinese counterparts at CNOOC Ltd. said they started production at the Liwan gas field in the South China Sea.
Asim Gosh, chief executive officer at Husky, said the Liwan field was a major accomplishment for his country.
"Liwan is Husky's largest project to date and places us inside the door of one of the fastest growing energy markets in the world," he said in a statement Sunday.
Combined, total gas sales from the area should reach 500 million cubic feet per day once all programs go online by 2017.
Husky said it expects to recover its $800 million in exploration from the project during the first 18 months of production.
Husky holds a 49 percent stake in the project alongside China National Offshore Oil Corp., Ltd., the majority shareholder.
There was no statement on the development from CNOOC.