CNOOC Ltd has achieved a major exploration breakthrough in an ultra-shallow gas play in ultra-deep water South China Sea, the state-owned oil and gas firm said on Thursday.

Its Lingshui 36-1 gas field, located in the western South China Sea, has been tested to produce over 10 million cubic meters per day of open flow natural gas.

"The successful testing of Lingshui 36-1 further expands the resource base for the development of a trillion-cubic-metre gas region in the South China Sea," CNOOC CEO Zhou Xinhuai said in a press release.

CNOOC will continue to step up exploration and development of hydrocarbon resources in the South China Sea and to enhance its energy supply capacity, Zhou added.

(Reporting by Siyi Liu and Colleen Howe in Beijing; Additional reporting by Aizhu Chen in Singapore; ; editing by Jason Neely)