BEIJING -- China's largest producer of offshore oil and gas CNOOC said Monday that CNOOC 981, the country's first deepwater drilling rig, has reported its first deepwater gasfield discovery below the South China Sea.

The newly-discovered Lingshui 17-2 gasfield is located 150 kilometers south of the Hainan Island. Its average operational depth was 1,500 meters below the sea surface, the company said in a statement.

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Xie Yuhong, a manager with CNOOC, said the Lingshui 17-2 gas well was tested to produce 56.5 million cubic feet of natural gas per day, equal to about 9,400 barrels of liquid oil per day.

It was the highest daily flow of all CNOOC's gas wells during testing, he said.

The Lingshui 17-2 well is also the first significant deepwater gas and oil discovery by semi-submersible CNOOC 981, which started operations in May of 2012.

It took 6 billion yuan ($975 million) and more than three years for China State Shipbuilding Corp. (CSSC), the contractor, to build the CNOOC 981 rig for CNOOC.

The platform is 114 meters long, 90 meters wide and 137.8 meters high, and weighs 31,000 tonnes.

With a deck the size of a standard football field, the rig is capable of undertaking an offshore operation at a maximum water depth of 3,000 meters and drilling a depth of 12,000 meters, according to CSSC.