Study On Pipeline Mechanical Characteristics Of Deep Sea J-Lay Installation

While the exploration of offshore crude oil and natural gas resources is being continuously moved to the deep sea field,pipeline installation technology is facing many challenges.Compared with other pipeline laying methods,J-lay method has many advantages for the deep sea pipeline installation,such as: natural overall shapes of pipelines,less requirement for the tension of the tensioner,relatively small stress and so on.Therefore,study on the J-lay method is of great significance.Mechanical property analysis of pipelines during deep sea J-lay installation is fundemental problem of the J-lay method.It is also one of the most important issues for J-lay method application to practical projects.This thesis firstly introduces the background and significance of the study based on reviews of a large number of pipeline laying literatures,especially pipeline mechanical properties of J-type pipe laying.A variety of pipe laying methods were introduced in detail while the advantages and disadvantages of different methods of pipe laying are compared.In addition,the research status of pipeline mechanics characteristics in J-lay installation is summarized in detail.Secondly,this thesis introduces calculation theory and analysis the hydrodynamic s of a pipe-laying vessel with AWQA.Thirdly,the calculation theory of pipeline in J-type laying process is introduced,and the finite element model of J-lay method is established.The reliability of the model is demonstrated by comparing the calculated results with the literatures.Fouthly,the static analysis and dynamic analysis of the pipeline are carried out.The effects of several important parameters(water depth,laying angle,outside diameter and wall thickness)with the pipe shape,internal force and stress have been studied in the static analysis and some general laws were obtained.The effects of wave and current load on pipe installation have been studied in the dynamic analysis.The effects of flow velocity and its distribution,wave height,period and different flow directions on pipelines are discussed respectively.Finally,pipe-laying capacity for light J-type laying system based on the static and dynamic analysis have been computed.The static and dynamic results are discussed respectively.The limitation of laying angles of different pipelines at different water depths have been studied.