Thermal-Structural Coupling And Seismic Response Analysis Of Deep Submarine Oil Pipeline

Submarine pipeline is one of the main ways to transport oil and gas on the sea and is an important part of offshore oil and gas field.Because the medium transported by submarine pipeline needs high temperature and high pressure to ensure its normal operation,if the pipeline leaks,it will cause a series of problems,such as the shutdown of offshore oil field,the difficulty of underwater maintenance,the pollution of marine environment,and so on.If oil spill accidents occur frequently and continue to increase,it will lead to the deterioration of marine ecology and produce serious negative social impact.Because the inner pipe of submarine oil pipeline itself bears the thermal stress produced by hot oil,but there are insulation layers between the inner and outer pipelines,the thermal stress of the outer pipeline can be neglected basically compared with the inner pipeline.When the inner pipeline leaks and the leakage mouth reaches a certain size,the local stress concentration of the leakage outlet exceeds the yield strength of the pipe,and fatigue fracture is easy to occur under the constant impact of various loads,which makes the leakage accident worse.Even if the leak of the inner pipeline does not damage the pipeline,it is very likely that the pipeline will be deformed or destroyed under the earthquake.Therefore,while the transportation mode of submarine pipeline is developing vigorously,the undersea is at the same time.The research of pipeline leakage is always a difficult problem.Once the submarine pipeline fails to leak,it is more difficult to maintain and replace the pipeline than the land pipeline,which not only affects the normal transportation of oil and gas,but also causes huge economic losses.And leaking oil and gas can cause long-term catastrophic pollution to the marine environment and organisms.Therefore,it is very important to study submarine oil pipelines with leak holes at high temperature and high pressure.In this paper,a finite element model of a leaky submarine pipeline is established by using ANSYS finite element software under different leakage port sizes,temperature,transport pressure and seismic stress factors.The specific contents of the study are as follows:1.Based on the basic theory of heat transfer,the calculation method and the convection heat transfer coefficient between sea water and submarine pipeline and between submarine pipeline and hot oil are given according to the heat transfer characteristics of deep-sea double-layer submarine pipeline.The realization method of thermal-structural coupling analysis in finite element method is analyzed,and the finite element model studied in this paper is established,and the indirect coupling method is used to solve the model.2.For the leaky sea pipe,three kinds of conditions are simulated and analyzed under the action of temperature,transportation pressure and temperature and transportation pressure respectively,and the results are analyzed through the analysis of the results.The critical temperature and pressure affecting the further damage of the leaking submarine pipeline are obtained.3.Based on the seismic response analysis of the non-leakage submarine pipeline and the submarine pipeline with different leakage caliber,the natural frequency and the main modes of the leakage pipeline are obtained,and the inner wall of the leakage and non-leakage sea pipe,the inner wall of the outer pipe,The outer wall is compared and analyzed.In this paper,the finite element model is established to simulate the leakage of inner pipe under thermal stress,and a series of influencing factors,such as leakage,thermal stress,submarine and earthquake,are studied and analyzed.The key factors leading to the failure of the submarine oil pipeline containing leakage in the inner pipe are summarized,and the guidance is provided for the normal maintenance of the submarine pipeline and the replacement of the pipeline section.