Recently, Zhi Yuan Kou, a 40,000-tonne semi-submersible vessel operated by COSCO SHIPPING Specialized Carriers, successfully transported China's largest mobile offshore oil and gas production platform—CNOOC's Hai Yang Shi You 166—from Tongzhou Bay to designated waters in the Beibu Gulf off Guangxi. The vessel also successfully completed the float-off and precision positioning operations for the platform.

"Precision positioning" refers to a critical operational term in offshore engineering, particularly within offshore oil and gas development. It denotes the process of moving and securing a jack-up drilling rig or production platform to a predetermined location at sea with an exceptionally high degree of accuracy, typically employed for drilling, workover, or platform installation activities.

The Hai Yang Shi You 166 platform represents China's largest, heaviest, and most technologically advanced self-installing mobile offshore oil production and processing facility of its kind to date. The platform has a total weight exceeding 11,500 tonnes, measures 85 meters in length and 46 meters in breadth, and integrates 3,953 sets of equipment. It combines core functionalities including full-process oil and gas treatment, intelligent monitoring, and living quarters support, and constitutes essential infrastructure for the development of the Weizhou 10-3 West Oilfield. Once operational, the platform will significantly enhance oil and gas production capacity in the Beibu Gulf region, contributing materially to safeguarding national energy supply and promoting high-quality development of the marine economy.

This operation also marked the first occasion that Tongzhou Bay has facilitated heavy-lift offshore engineering operations utilizing a powered semi-submersible vessel. COSCO SHIPPING Guangzhou Salvage Semi-submersible Transport Division served as the general contractor for this project, assuming overall responsibility for vessel operations and offshore execution. The Zhi Yuan Kou vessel, distinguished by its precise positioning capabilities, exceptional stability, and robust seakeeping performance in adverse wind and wave conditions, provided a solid hardware foundation for this highly challenging transport and subsequent precision positioning operation.

During the preparatory phase, the project team maintained close coordination with the shore-based command center, conducting meticulous assessments of route-specific meteorological and oceanographic conditions. Comprehensive procedures encompassing cargo securing, submerging and surfacing operations, navigational monitoring, and platform precision positioning were refined in detail, supported by repeated emergency drills to ensure readiness for complex offshore contingencies. Throughout the voyage, the entire crew remained diligently at their posts, maintaining continuous watch and strictly adhering to safety operating protocols. Navigational course and speed were precisely managed to overcome multiple challenges, including complex currents and variable weather, ensuring the stability of both vessel and cargo for the entire duration. Upon arrival in the Weizhou operational area, the project team leveraged extensive offshore engineering expertise to safely and successfully execute the float-off, towing, and precision positioning mating operations, ensuring flawless alignment between the platform and its subsea foundation. This professional execution safeguarded the successful installation of a critical national strategic asset.