HAIKOU, Sept. 26 (Xinhua) -- China's first independently-developed ultra-deepwater gas field Shenhai Yihao, or Deep Sea No. 1, has completed construction of its phase II project, which is expected to be operational in the near future, according to the China National Offshore Oil Corporation (CNOOC), its operator.

The completion of the project marks a major breakthrough in China's independent construction capabilities of deepwater oil and gas projects under complex conditions, the CNOOC said Thursday.

The phase II project, with a proven reserve of over 50 billion cubic meters of natural gas, includes 12 deepwater gas wells, a comprehensive processing platform weighing over 14,000 tonnes and five submarine pipelines with a total length of about 250 km, among other facilities.

Upon full operation of the project, the peak annual output of natural gas of the Deep Sea No. 1 is expected to increase from 3 billion cubic meters to 4.5 billion cubic meters, according to the CNOOC.

Deep Sea No. 1, located 150 km from the city of Sanya in south China's island province of Hainan, is able to operate at a maximum depth of over 1,500 meters in the sea. It began operation in June 2021.