Study On Running And Installation Dynamics Of Subsea Tree

Along with the development and utilization of offshore oil and gas resources to the deep water,subsea tree installation under decentralization also increased the difficulty,the safety in the process of decentralization put forward higher request.The platform-drill pipe-subsea tree system was taken as the research object,and the coupling dynamics of the process of drill pipe lowering was analyzed,and the operation window of drill pipe lowering and installing subsea tree was determined.Firstly,the technology of the lowering of the underground subsea tree was studied,compared with the advantages and disadvantages of different methods,and the appropriate technology of the lowering was chose.Then,the research status of dynamic analysis of downward installation process of subsea tree and the analysis method of operation window are investigated,and a reasonable and feasible dynamic analysis method was formulated based on the investigation results.Secondly,by establishing the theoretical model of platform-drill pipe-subsesa tree longitudinal dynamics,the natural frequencies,main modes and vibration responses of drill pipe are solved by using the top and bottom boundary conditions of drill pipe.In order to study the transverse offset and shear force of drill pipe in the process of drill pipe lowering,considering the combined action of wave and current,a mechanical model of transverse vibration of drill pipe lowering was established,and the influence of ocean current on the mechanical characteristics of drill pipe was analyzed.Then,the coupling dynamic analysis model of platform-drill pipe-subsea tree system was established by Orcaflex,and the dynamic response analysis of drill pipe under the combined action of platform and wave-current was completed.Compared with the theoretical value,the correctness of the simulation results was verified.By analyzing the influence of environmental variables on the dynamic response of drill pipe,the following conclusions were drawn: with the increase of ocean current velocity,the lateral offset,longitudinal offset and maximum equivalent stress of drill pipe increase correspondingly,while the longitudinal velocity of lower end point basically remains unchanged;with the increase of wave height,except for the lateral offset of drill pipe,the dynamic response of drill pipe increases significantly,and its change.The law was basically the same;with the change of wave period,the variation period of the longitudinal offset of drill pipe changes,but the variation amplitude was basically unchanged,and the variation amplitude and period of the maximum equivalent stress of drill pipe and the velocity of lower end point change.Finally,the drill pipe installation criteria for underwater subsea tree were determined.According to the results of dynamic response analysis,the sensitivity of drill pipe parameters was analyzed by orthogonal test method.The results show that the most important factors affecting drill pipe offset,equivalent stress and end velocity were currents,wave periods and wave heights.In view of the main influencing factors,the downward installation window of the drill pipe of the subsea tree was calculated to provide theoretical guidance for the downward installation process of the drill pipe of the subsea tree.