CNOOC has been stepping up cooperation with international oil companies in recent years including Hague-based Royal Dutch Shell, California-based Chevron, Houston-based ConocoPhillips, France's Total, Norway's Equinor, Kuwait Foreign Petroleum Exploration, Calgary-based Husky Energy, Sydney-headquartered Roc Oil and South Korea's SK Innovation to seek oil and gas in offshore China.

CNOOC, which has teamed up with Canada-based Husky Energy for the Liuhua gas field, said it would step up its cooperation with other foreign companies for offshore gas production so as to ensure stable domestic supplies.

The Chinese oil major has a 25 percent working interest in the Liuhua 29-1 project and acts as the shallow-water operator, while Husky, which is in the midst of being taken over by compatriot Cenovus Energy, holds the majority 75 percent stake and acts as the operator in the deep water.

CNOOC and Husky had earlier teamed up for the Liwan 3-1 gas field, which was put into operation in 2014, marking the first step in the development of deep water gas in the South China Sea.

The State-owned company announced on Tuesday it has signed a strategic agreement with partners including British-Dutch oil and gas firm Royal Dutch Shell Plc, US Chevron Corp, US ConocoPhillips, French Total SA, Norwegian Equinor ASA, Canadian Husky Energy Inc and Australian Roc Oil Co.

According to CNOOC, the company has been stepping up cooperation with international oil companies in recent years, including Hague-based Royal Dutch Shell, California-based Chevron, Houston-based ConocoPhillips, France's Total, Norway's Equinor, Kuwait Foreign Petroleum Exploration, Calgary-based Husky Energy, Sydney-headquartered Roc Oil and South Korea's SK Innovation to seek oil and gas in offshore China.