The Nonlinear Static Analysis Of Pipeline During Ultra-Deep Installation

With the depletion of oil and gas resources on the land, more and more attention has been paid to offshore oil and gas around the world. Subsea pipeline is a vital part of the development and transportation system of the offshore oil and gas resources,so it has been known as the petrochemical lifeline. With the development of offshore oil and gas resources in our country, it will create a great demand on subsea pipelines in the future.The subsea pipeline bear the bending moment,tensile force,ocean curret force and static water pressure in the process of pipelaying,so it is a big challenge to ensure the safety of the pipelines.So the research on the pipeline mechanic in the process of pipelaying is particularly important.We use the theory of large deformation to establish the nonlinear governing differential equation in the process of S-Lay and J-Lay pipelaying,then we use the theory of singular perurbation to solve the equation and we obtain the singulay perturbation solution.To prove the correctness of the theoretical solution,we use the finite element method to solve this proplem.The results show that the finite element solution and singular perturbation solution are all correct.At the same time, on the basis of theoretical research, we use the singular perturbation analysis program for the S-Lay and J-Lay to do the parameter sensitivity analysis.Also we summarize the influence on pipeline configuration and stress state under different working condition,such as different water depth and different current force.Then we give technical advice in the process of pipelaying and provide theoretical reference for deepwater pipelaying process.Finally, this paper combines the Delphi language and MATLAB software to develop the submarine pipelaying software.Because of the friendly interface, rapid calculation,it can be convenient for pipelying design.In this paper,the main research contents can be summarized as the following aspects:(1) The paper introduces the background and significance of pipelaying both in China and abord. Especially introduce the S-Lay and J-Lay pipelaying characteristic, mechanical properties and related research results in detail.(2) In this paper, we have considered the current force and the Brazier effect of pipe section, then we use the theory of large deformation to establish the nonlinear differential equation in the process of submarine pipelaying.And we obtain the pipeline configuration by using the theory of singular perturbation approximation theory.(3) We use the finite element numerical simulation method for deepwater pipelaying process.Through the comparison of finite element solution and singular perturbation solution, it verifies the correctness and rationality of the content of this article.(4) We use the approximate solution of singular perturbation to develop the software for pipelaying design.It provides a convenient way to analysis the pipeline;At the same time, we use the singular perturbation analysis program to do the parameter sensitivity analysis for the S-Lay and J-Lay method.