Study On The Performance Of Dynamic Positioning System During S-Lay Operation

As the great exploration and development of deep-sea resource,especially the transportation of the oil and gas from the sea,the pipeline has played an indispensible role in the advancement of the ocean career.It also builds a bridge allowing people to have access to the ocean oil and gas resource.Because of the complexity of the pipe laying technology,people have done much research on this field for decades.However,there are still many challenges for us to overcome.One of the most common methods for pipe laying is using the S-lay technique which is the most efficient and economical mean.The S-lay barge has been developed four generations,and now it applies the dynamic positioning system instead of the mooring system which used to be applied.In this paper,the ‘HYSY 201' deepwater pipelay vessel is the research object.By using the External Function of the business software Orcaflex,the dynamic positioning system calculation model has been developed based on PID control and Kalman filter theory.In addition,the thrust allocation was based on Sequential Quadratic Programming method.Meanwhile,the stinger-pipeline-barge coupling model was built for the analysis of the time-domain simulation of the dynamic positioning system during S-lay operation.The roller of stinger is simulated by the generalized elastic contact theory.The stinger is composed of Morrison members.Force on pipe is calculated by lumped mass method.The performance of dynamic positioning system was analyzed by two models.One model was just the simulation of the vessel motions without S-lay operation while another was the simulation of the vessel motions during S-lay operation.Then the performance of the dynamic positioning system and power consumption was discussed based on the difference simulation results between two models.For analyzing the influence of different laying depth and environmental load on the thrust system,four S-lay models was established of which laying of pipeline can reach respectively to 145 m,1175m,2000 m and 3000 m.Combined with environmental load with the direction 90°,135° and 180°,the thrust allocation and power consumption were analyzed for four S-lay models.In order to analyze the influence of the first-order motions of the vessel on the dynamic positioning system and the acting force of the pipeline,two groups of comparing models were built.One simulation group was made up of a S-lay vessel without first-order motions and a S-lay vessel with first-order motions.The influence of the first-order motions on DP accuracy was analyzed by comparing the difference between two models.Another simulation group consisted of a S-lay vessel with heave,surge,sway and yaw and a S-lay vessel with pitch,surge,sway and yaw.The influence of heave and pitch of the vessel on the acting force of pipeline was analyzed by the research on the simulation results of the two models.