China's first self-developed ultra-deep-water gas field, Shenhai-1, reached full production on Wednesday, becoming the country's largest offshore gas field by output, according to operator China National Offshore Oil Corp (CNOOC).

All 23 subsea wells at the field are now in operation, reaching a peak daily capacity of 15 million cubic meters, it said.

The full commissioning is a key step for China in achieving large-scale deep-sea oil and gas development through the construction of deepwater gas field clusters, CNOOC said. It is significant for safeguarding national energy security, driving regional economic development, and the building of a strong maritime nation.

Shenhai-1 was developed in two phases, with work on phase one beginning on June 25, 2021. The field has proven natural gas reserves exceeding 150 billion cubic meters and operates in water depths below 1,500 meters, with well depths exceeding 5,000 meters.

CNOOC has described Shenhai-1 as China's deepest and most challenging deepwater gas field to be developed to date, with temperature and pressure levels exceeding those in comparable fields.

With all wells online, the field has reached its peak design capacity, with expected annual gas output exceeding 4.5 billion cubic meters.

The deepwater natural gas is transported via onshore terminals in the Hong Kong Special Administrative Region, Sanya in Hainan, and Zhuhai in Guangdong province, supplying industrial and residential users in the Guangdong-Hong Kong-Macao Greater Bay Area, and the Hainan Free Trade Port. It is also connected to the national natural gas pipeline network.