China's CNOOC Ltd. (NYSE: CEO) said on Feb. 26 tapped the country's first ultra-deepwater natural gas discovery in the northwestern part of the South China Sea.

The state-owned offshore oil and gas explorer started to drill the Lingshui 18-1-1 exploration well last October in water depths of 1,688 meters (5,538 ft) and a test of the well in December was a success, the company said in a report published on the website of parent company China National Offshore Oil Corp.

An "ultradeep" well is categorized as one more than 1,500 meters (4,921 ft) under the sea.

The report didn't give any estimate of gas flows at Lingshui 18-1-1, but said the discovery has been certified by the Ministry of Land & Resources.

It's located next to another deepsea gas find Lingshui 17-2, which has certified proven reserves exceeding 100 billion cubic meters as reported by the state media a year ago.

CNOOC deployed the country's flagship deepwater rig, the "Haiyang Shiyou 981", to drill the well, the report said.