An integrated subsea wellhead system independently developed by China has been successfully applied on an oil and gas platform in the Wenchang sea area off south China’s tropical island province of Hainan, according to the China National Offshore Oil Corporation (CNOOC) — the operator of the oil and gas platform — on Tuesday.
The successful application of the integrated subsea wellhead system signifies a leapfrog progress by China in the construction of offshoare oil and gas platforms, and also realization of more economical and effectual development of offshore oil fields by the country.
The subsea wellhead system is the central hub that connects underground oil and gas resources with the drilling equipment. The system newly developed by China is three meters tall and weighs a total of six tons. It is capable of operating at the area 500 meters beneath the sea surface, under high temperatures of up to 120 degrees Celsius and pressures of up to 70 megapascals.
“The installation and application of the ‘integrated undersea wellhead system’ have undergone five offshore trial operations under the most adverse working conditions. So far, all functions and applications of the wellhead system have proven to be normal, and the drilling operation of an oil well has been efficiently completed,” said Zheng Jinlong, project manager of CNOOC Limited’s Zhanjiang Branch.
Under the traditional system of offshore oil and gas platform construction, a foundation needs to be laid at the seabed in advance for holding the subsea wellhead system, which is equivalent to the prior construction of a weight-bearing undersea foundation. Then, on the foundation, a pipeline for oil and gas production that can withstand high temperature and pressure would be built.
In developing the integrated undersea wellhead system, the CNOOC technicians made a new design to achieve combination of the two types of wellhead and equipment with different sizes and functions.
“Instead of laying the foundation first and building the passage second, the approach now is to simultaneously establish the foundation and the oil and gas production passage. This method is over 40 percent faster than the conventional way of well construction, and the average cost saving of each well is about 3 million yuan (over 414,000 U.S. dollars),” said Huang Yi, manager of the engineering operation center of CNOOC Limited’s Zhanjiang Branch.
The newly developed integrated subsea wellhead system is applicable to most of the semi-submersible drilling platforms in China after completion of drilling operations.
There are a total of 15 semi-submersible drilling platforms in China. After the large-scale application of the newly developed integrated subsea wellhead system, the annual cost can be saved by about 60 million yuan (about 8.29 million U.S. dollars), which is of great significance to reducing costs and further promoting economical and effective development of offshore deepwater oil and gas fields.