Detection And Vibration Characteristic Analysis Of Submarine Pipeline Suspension Span Section

As the most important transportation method for offshore oil and gas resources,submarine pipelines are the lifeline of offshore oil and gas fields.If the overhanging submarine pipeline cannot be detected in time,with the increase of the overhanging length,the fatigue fracture will easily occur under the action of the sea current due to eddy vibration.The research is carried out on the basis of side-scan sonar image processing method and the basic theory of pipe span vibration using finite element analysis software for computational simulation.Firstly,based on the measured submarine pipeline side-scan sonar images,different denoising algorithms are applied to program the denoising process through MATLAB software platform,and the resultant images are analyzed in terms of subjective and objective evaluation to explore the algorithm with better denoising effect for the submarine pipeline side-scan sonar images.Based on the study of sonar image denoising,a new sonar image segmentation method is proposed based on the idea of first using denoising methods to eliminate the interference of noise in the image,and then using image segmentation algorithms to segment the sonar image,and its effectiveness and superiority are verified by comparison with traditional segmentation algorithms.Secondly,the sonar images and bathymetric 3D images obtained from the submarine pipeline inspection in Zhoushan sea area are combined to interpret the type and parameters of the overhanging span section,so that the vibration characteristics of the overhanging span section can be studied.According to the maximum allowable overhang length of the pipeline calculated by different methods,the appropriate overhang length is selected,and the single-span and double-span submarine pipeline models are established by using ABAQUS finite element software to explore the vibration characteristics of the single-span pipeline with different boundary conditions at both ends,as well as to discuss the influence of the inter-span support soil length and the neighboring span length on the vibration characteristics of the main overhang section in the calculation model of the double-span submarine pipeline,and to analyze the trends of the parameters such as the natural frequency and the vertical vibration displacement amplitude of the pipeline,so as to provide help for the treatment of overhanging pipelines in practical engineering.Finally,the vibration characteristics of the overhanging pipe under the combined action of internal and external flow are explored to explore the influence of internal flow on the vibration of the overhanging pipe.Under the conditions of different internal flow velocities and different internal flow media,the finite element software is applied to simulate and analyze the overhanging pipeline,and the corresponding vibration displacement time course curves of the middle section of the overhanging pipeline and the vibration patterns and motion trajectories of the pipeline in the cross-flow and down-flow directions are obtained.The research results show that the change of inter-span support soil length and neighboring span length in the double-span submarine pipeline has a greater impact on the main span vibration,and the change of internal flow medium has a greater impact on the vibration of the overhanging span pipeline compared with the internal flow velocity.