Electric Heating Design And Buckling Analysis Of Submarine Pipeline

With the development of deep-sea oil and gas,the low wax point of heavy oil has become a major problem affecting the efficiency and safety of offshore oil and gas production.In order to ensure the transportation safety of deep-sea oil and gas exploitation,the electric heating technology of submarine pipelines has received more attention at home and abroad.The direct electric heating technology of submarine pipeline is an effective technology for insulation and unblocking of submarine pipeline.The main factor affecting the direct electric heating technology of submarine pipeline is the large energy consumption of electric heating.The submarine pipeline is prone to thermal buckling failure due to the accumulation of a large amount of heat on the pipe wall.In order to reduce the energy consumption of the electric heating of the submarine pipeline,this paper analyzes the influence of the diameter to thickness ratio of the submarine pipeline and the thickness of the insulation layer on the electric heating efficiency of the submarine pipeline according to the melting of the heavy oil inside the submarine pipeline and the temperature of the pipe wall,and carries out the structural optimization design of the submarine pipeline.After the structural optimization of the submarine pipeline,the optimal electric heating power is selected on the premise of ensuring the safety of the electric heating of the submarine pipeline.In the past,the single uniform temperature load was mostly used in the thermal buckling analysis of submarine pipelines.In this paper,based on the temperature distribution of submarine pipelines under electric heating and the existing outage and maintenance conditions of submarine pipelines,the transverse thermal buckling analysis of submarine pipelines with non-uniform temperature under cyclic load was carried out.Aiming at the transverse thermal buckling of submarine pipeline,the effect of serpentine pipe laying method on the transverse thermal buckling of submarine pipeline under cyclic load is analyzed.In this paper,a nonlinear finite element model of a submarine pipeline with non-straightness defects,which is laid bare on a rigid seabed,is established.The effects of the interaction between pipe and soil,heating temperature and the number of cycles on the lateral buckling were studied under multiple start-stop cycles.The results show that the transverse friction coefficient has a great influence on the transverse thermal buckling,and the influence of the axial friction coefficient on the transverse thermal buckling of the submarine pipeline is smaller than that of the transverse friction coefficient.With the increase of heating temperature,the deformation of submarine pipeline is less affected,but the maximum stress of submarine pipeline will increase.With the increase of startup and shutdown times,the transverse thermal buckling of submarine pipelines will gradually stabilize.The non-uniform temperature load caused by the electric heating and unblocking of the submarine pipeline will increase the maximum stress of the submarine pipeline,thus reducing the service life of the submarine pipeline.The sine wave wavelength and amplitude of the serpentine pipe laying method are analyzed.The results show that the serpentine pipe laying method has little influence on the transverse thermal buckling deformation of the submarine pipeline under cyclic load,but can significantly reduce the maximum stress of the submarine pipeline.