Study On Force Of Initial Pipelaying In The Deepwater S-lay Operation And Its Application In Simulation System

Submarine pipeline is the main way of transporting offshore oil and gas resources,compared with the pipeline laying on the land,it is more complicated in the complex marine environment which is full of all kinds of adverse factors,meanwhile putting forward the higher demands to operators. During pipe laying, due to the existence of the current and wave,the pipeline will be subjected to various bending stress. The movement mode of the vessel in the wave will also lead to the change of the shape and stress of the pipeline. Based on the actual operating environment of "HYSY2O1", the shape and force of the pipeline and the dynamic response of the pipe by the current, wave and the pipelaying vessel is studyed.Accurate simulation of the shape of the pipe and the cable in the initial pipelaying is helpful to create a lifelike scene effect about pipelaying operation of the deepwater pipelay crane vessel.(1) For pipelaying operation simulation system, Multi-channel discrete data exchange model based on DP, visual scene, tensioner and mathematical model of pipe laying has been build up.At the same time a variety of factors influence on pipe laying were considered according to actual pipe laying operation process.For example, sea conditions, dynamic positioning, pipe laying vessel and so on. Thus the internal data communication of the whole simulation system is realized. According to the requirements of the simulation system and the analysis of various algorithms, the method of initial pipe laying is determined, and the program is realized.(2) The static force of the pipe and cable in the initial S-lay is analyzed. First of all, the differential equation of pipeline is established by building natural coordinate system, the nonlinear differential equation is discretized by using differential method and solved by numerical method.Thus the shape and internal force of the pipe joints are calculated. and cable model is built and solved by iterative method;Finally, the accuracy of the mathematical model was vertified, and the influence of the current on the shape and the stress of the pipeline is analyzed.(3) In view of the actual operation of the pipelaying vessel, studying the effects of the sea conditions and dynamic positioning on pipeline. Firstly, the mathematical model of wave load is established according to the marine operating environment and linear wave theory,and the mathematical model of the vibration of the pipeline is deduced. The displacement and internal force of the pipeline is calculated by using a suitable numerical algorithm; The influence of the wave on the pipeline and the real-time change of the critical position of the pipeline are analyzed by specific example of initial pipelaying.(4) The joint test of pipelaying simulation is conducted combining with each subsystem of pipelaying simulation.The function of simulation system and algorithm simulation theory are vertified. For specific case of pipelaying, the simulation platform of pipelaying run stably,visual images showed smoothly and the real-time comunication was fast and accurate. On the basis of simulation platform ,the pipe's response under the condition of hull exciting is analysed and tension test is made. The practical example shows that the algorithm can be applied to the initial S-laying effectively, which contributes to the preview of offshore pipe laying operation,feasibility analysis and optimization of operation plan.