The Research About Mooring Assisted Dynamic Positioning Of Semi-submersible Tender Support Drilling Unit

With the marine petroleum development tending towards deep sea, offshore platform is facing more and more extreme ocean environment, the positioning form of traditional mooring positioning and dynamic positioning are becoming increasingly unable to meet the working requirements of deep water depth and the increasingly harsh working environment.Therefore, the emergence of the mooring assisted dynamic positioning provides a new way for the location of deep-water oil and gas exploitation. Compared with the mooring positioning and dynamic positioning, the mooring assisted dynamic positioning has the advantages of high precision、good flexibility、adapting to the extreme sea conditions、good safety, showing good working performance in the deep sea oil and gas development; at the same time, with the water depth of drilling operation being more and more deep, the requirement of variable load of drilling platform is more and more rigorous. The concept of tender support drilling unit breeds out in this context,semi-submersible platform become the first choice for tender support drilling unit due to its excellent performance.In this paper,a tender support drilling unit is studied, analysis program of the mooring assisted dynamic positioning was programed due to the principle of mooring assisted dynamic positioning, and location capability was verified under different working conditions.The kinematic equation for the mooring assisted dynamic positioning, including motion equation of wave frequency and motion equation of low frequency ware established in this paper. Empirical formula was used to calculate the wind load, current load, and the Newman approximation theory was used to calculate wave two order load. the catenary mooring system calculation program was programed based on catenary theory, and then compared to the commercial software-Aqwa to verify the accuracy of the program, particle swarm optimization thruster allocation method and particle swarm optimization PID control method ware introduced and designed afterwards, and the algorithm was programed using MATLAB,the feasibility of the algorithm was verified through a specific numerical example.Static and dynamic positioning capacity of mooring assisted dynamic positioning of tender support drilling unit ware analyzed,the extreme wind speed curve of tender support drilling unit was drawing, and then tender support drilling unit was analyzed by time-domain algorithm based on quasi static dynamic. The results ware compared with the mooring,mooring assisted dynamic positioning can well control the position of tender support drilling unit, reduce the stress of the mooring system, numerically further verify the superiority of the mooring assisted dynamic positioning.The Aqwa software was second redeveloped aimed at the analysis of positioning ability of service condition of the semi-submersible tender support drilling unit,a PID control method based on the two platform center of gravity relative coordinates was designed, the particle swarm thrust allocation algorithm was incorporated into the second redeveloped program. Compared to mooring, the calculation results show that the mooring assisted dynamic positioning program of this paper designed can better control the relative gravity center position of two platforms.