An aerial drone photo taken in April, 2025 shows the Deep Sea No. 1 energy station, in south China's island province of Hainan. [Photo/Xinhua]

China National Offshore Oil Corporation (CNOOC) announced Wednesday the full operation of the second phase of its flagship gas field in the South China Sea, marking the completion of the country's largest offshore natural gas development to date.

The progress brings the gas field, named Shenhai Yihao or Deep Sea No. 1, to its designed production capacity of 4.5 billion cubic meters annually, according to CNOOC, the largest offshore oil and gas producer in China.

The gas field boasts proven geological reserves of over 150 billion cubic meters of natural gas. Production of phase-one project commenced in June 2021.

Natural gas extracted from the field is transported to coastal terminals in Hong Kong, Sanya in Hainan, and Zhuhai in Guangdong, supplying key economic regions while integrating into the national gas pipeline network.

The second phase of the project represents the country's most challenging deepwater gas development so far, as it operates under the highest temperatures and pressures ever encountered in domestic offshore exploration. Additionally, it is China's deepest gas development, functioning at water depths exceeding 1,500 meters and well depths surpassing 5,000 meters.

Project manager Liu Kang said the production infrastructure and technical expertise established through the project will help future complex deepwater oil and gas exploration, enhancing the role of marine resources in supporting national energy supply.