On April 16, the world’s first “integrated underwater wellhead system” independently developed by China was successfully applied. This system can speed up the surface well construction phase of underwater drilling by more than 40%, effectively solving the problems of engineering difficulty, long operation time and high cost of the traditional underwater wellhead system, which is of great significance in promoting the high-quality development of China’s offshore oil industry.
The underwater wellhead system is the key equipment for deepwater oil and gas exploration and development, which plays an important role in the offshore oil drilling and oil and gas production process. The system generally consists of internal components such as guide substrate, low-pressure wellhead head, high-pressure wellhead head and casing hangers. It is installed near the seabed, connected downward to the oil and gas production pipelines of the wells to form a closed oil and gas production channel, and upward to the large equipment such as the underwater oil recovery tree and the underwater blowout preventer set, and supports their weight.
This time, the ” integrated subsea wellhead system” independently developed by CNOOC has made a new structural design for both the traditional subsea wellhead system and casing structure. CNOOC has overcome nine technical difficulties, including wellhead stability study, one-piece wellhead head structure design, variable diameter casing structure design and service tool capability upgrade.
The overall weight of the wellhead system is about 6 tons and the total length is 3 meters. It is suitable for water depths of 500 meters and pressure ratings of 70 MPa, and it can be further upgraded to meet most semi-submersible platform drilling and completion applications worldwide.
It is understood that there are 15 semi-submersible drilling platforms in China, drilling more than 50 exploration wells every year. After the large-scale application of the “integrated underwater wellhead system”, the drilling period can be saved for more than 30 days per year, and the cost can be saved for about RMB 60 million.