Deepwater semi-submersible platform is the mainstream production mode for offshore oil and gas field development at home and abroad. After the semi-submersible production platform is built, the platform transportation mode is determined according to the towing distance. If the semi-submersible platform is far away from the installation site, the semi-submersible platform shall be towed to the sea area suitable for loading by dry towing. The transportation vessel shall dry tow the semi-submersible to the predetermined sea area for unloading, and then wet tow the platform to the installation site. Taking Lingshui17-2 semi-submersible platform as an example, this paper conducts hydrodynamic analysis on dry towing of transportation vessel through 3D potential flow analysis software, studies the six degree of freedom motion response under the combined action of wind, wave and current, conducts time domain analysis, calculates the motion from time domain analysis for 10-year non-cyclone conditions of dry towing key points, and conducts comparative analysis in combination with model test. In addition, the water immergence analysis of FPU when dry tow under typical transport conditions is carried out to ensure transport safety, which provides a theoretical basis for the safety of dry towing of FPU. The calculation method can be used for reference by similar projects and is of great significance.
Deepwater semi-submersible platform is the mainstream production mode for offshore oil and gas field development at home and abroad. After the semi-submersible production platform is built, the platform transportation mode is determined according to the towing distance. If the semi-submersible platform is far away from the installation site, the semi-submersible platform shall be towed to the sea area suitable for loading by dry towing. The transportation vessel shall dry tow the semi-submersible to the predetermined sea area for unloading, and then wet tow the platform to the installation site. Taking LS17-2 semi-submersible platform as an example, the deep draft semi-submersible platform operated by CNOOC for LS17-2 gas field located in the northern South China Sea is transported by dry tow method using XGH semi-submersible vessel operated by COSCO. The dry transportation of the LS17-2 semi-submersible platform is from the shipyard in Qingdao to float off location in Sanya.
