"Deep Sea No. 1" Phase II Fully Operational: China's Largest Offshore Gas Field Completed

On June 25, in the waters off Yacheng, Hainan, the "Deep Sea No. 1" Phase II project achieved full production as the last gas well was brought online. This marks the official start of operations for all 23 subsea gas wells at the Deep Sea No. 1 large-scale gas field, with a peak daily output reaching 15 million cubic meters—making it the country's largest offshore gas field in terms of production capacity.

The "Deep Sea No. 1" gas field is being developed and constructed in Phase I and Phase II. Phase I of the project came on stream in June 2021. Phase II, meanwhile, is divided into three well areas—South, North, and East—where 12 subsea gas wells have been deployed. The phase also includes the construction of one new jacket platform, a complete set of subsea production systems, five seabed pipelines, and five deepwater umbilical cables. Together, these facilities form an ultra-large-scale oil and gas production cluster that spans over 170 kilometers in geographic distance and operates at water depths exceeding 1,500 meters.

The second-phase project's development and construction face more complex natural conditions, as illustrated clearly by a set of data:

“Deep,” with 12 underwater gas wells collectively exceeding 60,000 meters in total depth—equivalent to nearly seven Mount Everests stacked atop one another; “High-Temperature,” where formation temperatures soar as high as 138 degrees Celsius; and “High-Pressure,” with formation pressures peaking at 69 megapascals—roughly 1,000 times the operating pressure of a typical household pressure cooker…

“The construction of offshore wells and the establishment of subsea production systems pose significant technical challenges, and there are no global precedents to draw from,” Wang Heng, Completion Director of CNOOC’s “Deepwater No. 1” Phase II project, told reporters.

Why tackle the "hard nut"? In China, offshore oil and gas has become the "main battlefield" for boosting oil and gas production—by 2024, the increase in offshore crude oil accounted for about 80% of the nation’s total crude oil growth. And among offshore oil and gas resources, roughly two-thirds of recent new discoveries have been concentrated in deepwater areas over the past few years.

Wang Heng explained that, to ensure the smooth commissioning of the Phase II project, the technical team collaborated with universities and research institutions to conduct targeted research, resulting in the development of five world-first key technologies for deepwater high-pressure well drilling and completion. These breakthroughs have also spurred the localization of a range of equipment and products, boosting overall operational efficiency by more than 30%.

Beyond technological breakthroughs, there’s also innovation in operational models. The second-phase project has pioneered an industry-first development model—combining an "underwater production system," a "shallow-water jacket platform," and a "remote control system for deep-water semi-submersible platforms." This groundbreaking approach has transformed the nearly 30-year-old production facilities of the shallow-water gas field into a vital hub for oil and gas transportation, enabling deep-water hydrocarbons to be efficiently routed here for comprehensive processing.

It is reported that the "Deepsea No. 1" gas field has now reached its maximum designed production capacity, with annual gas output expected to exceed 4.5 billion cubic meters. The deepwater natural gas produced at the field can be delivered via onshore terminals in Hong Kong, Sanya, Hainan, and Zhuhai, Guangdong, reaching the Greater Bay Area of Guangdong, Hong Kong, and Macao, as well as the Hainan Free Trade Port—and ultimately integrated into the national natural gas pipeline network.

Source: People's Daily