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Components of World's Largest Trussed Semi-Submersible Platform Completed

Updated: 2020-10-23

The components of the world's largest trussed semi-submersible platform independently designed and built by China National Offshore Oil Corporation (CNOOC) were recently loaded in CNOOC's Qingdao fabrication yard in Shandong province.

The loading marked progress in designing and manufacturing of China's deepwater ocean engineering equipment.

Consisting of 23 deck pieces with nearly 200 sets of key oil and gas processing equipment, the components feature residential space for 120 people.

Installed with 430,000 meters of cables, the components have a designed weight of nearly 20,000 tons, equaling the total weight of 200 extra-heavy trucks.

According to Han Shaoning, deputy general manager of CNOOC's Lingshui 17-2 offshore gas field development project where the semi-submersible platform is to be used, the trussed structure is lighter and needs less steel compared to the traditional box type semi-submersible platform. However, it calls for more complicated force calculation as well as higher requirements in fatigue properties, weight control and precision control.

The components will be the first to be used in a 1,500-meter deepwater high-pressure oil and gas field in China, and the technological process and the oil and gas processing system supporting them are also the most complex among those of domestic offshore oil and gas platforms, Han added.

According to Liu Xinyu, manager of the topside module department of the Lingshui 17-2 project, ultra-high strength steel was used in their construction, the first such use in China.

Higher requirements in material control and welding skills were also made. For example, with a largest span of 50 meters between main pillars, the tolerance should be less than the diameter of a pencil, which is the strictest in the industry.

What's more, it was the first time the finished supporters were used in a plate supporting residential living on such a platform. The intense cross joins and interference necessary during hoisting added to the difficulty of the components' construction.

Construction of the components started in May 2019. Several groups focusing on risk, precision and weight control were established and information tools like delicacy and visual management systems were used to improve engineering efficiency.

The components will be shipped to Yantai in Shandong and be assembled with the main body completed on Sept 28, which will form the world's first 10,000-ton semi-submersible oil storage platform.

Once operable it will be the first semi-submersible platform used for deep sea gas exploration in China.



(Executive editor: Wang Ruoting)

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