Analysis And Research On Towing Performance Of An Oil Production Storage And Offloading Jack-up Platform

Jack up platform with production storage offloading function which is one of the main equipment for the production of offshore oil and gas production in relatively shallow waters is playing an important role in marginal oilfield exploitation. After the platform was built, it should be transported to the working area and migration between the oil well also needs for towing work. Common towing mode includes dry towing and wet towing modes, dry towing depends on semi-submersible barge or semi-submersible transportation carriers and wet towing depends on its own buoyancy with the help of tug pulling force to migrate. In general, dry towing is easier than wet towing. Up to now, during the world’s occurred accidents in ocean engineering, the highest proportion are Jack up platforms and in these incidents the towing accidents occupy larger proportion. So it is necessary to research and study the Jack-up’s wet towing performance.This paper bases on a type of self elevating production storage and offloading platform which is designed by MARIC for North Gulf of south China sea as the research object, firstly to execute frequency analysis of zero speed of this platform in a regular waves and then the nonlinear time domain analysis is carried in real sea state by a tug- towing line-been towed platform composition system. The main research contents are as follows:1、Frequency domain wave induced load and motion response analysis of this Jack-upStudying on wave induced load and motion response of this zero speed Jack-up in linear regular waves in order to understand its preliminary motion performance. In real sea state, the typical section’s vertical force and moment and the 6-degree freedoms are predicted.2、Influence factors analysis of this Jack-up towing systemsBased on the frequency domain analysis, time domain coupled analysis is executed through hydrodynamic software AQWA-Drift module. Overall considering the influence factors during the wet towing: wind load, current load, towing line length, towing speed, trim and up pitch, shallow water effect, combined effect of wind wave current, hunting for practical conclusions for towing practice.3、Motion response mechanism and second order wave added resistance analysis during the wet towing with a single tugTaking wave frequency motion and low frequency motion decomposition using the computed motion response, and calculate the full frequency response energy spectrum Analysis and exploring yaw, sway long period low frequency response and the response mechanism of heave, roll wave frequency motions. Parameter sensitivity analysis was conducted for the second order wave force additional resistance force in the wet towing..4、Multi-tug towing’s numerical simulation and analysisIntroducing kinds of multi- ship towing scheme and analyzing its application range and the tug configuration.On the basis of single ship towing system model, establishing multiship towing system model, and two ship towing in nonparallel with different angles between two towing lines, parallel towing with different towing distance is optimized. Analyzes the two different three ship towing model and then conducting optimization.