Marine Riser Motion Monitoring Data Processing Method And Application

With the continuous development of offshore oil and gas development,it has been the trend for offshore oil and gas fields to move into deep water.The importance of marine risers in the offshore oil production system and the serious consequences of damage to marine risers determine that the safety of marine risers is a point that cannot be ignored in offshore oil production.In order to ensure the reliability of riser production,this thesis uses motion monitoring devices to carry out corresponding monitoring operations on marine risers,and through the processing of monitoring data and fatigue life analysis,the fatigue damage and fatigue life prediction of key parts of the riser system are tracked and recorded,thus ensuring the structural integrity of marine risers and the safety of underwater operations.First,in this thesis,the parameters related to the modal clarity index and the configuration clarity index are corrected using a linear regression method.Through the modal analysis of the flexible riser,the optimized arrangement of the motion monitoring device is completed by considering the effect of external loads such as wind,waves and currents as well as the influence of the weight of the outer protective shell and clamps of the motion monitoring device on the flexible riser.After that,the verification of the motion monitoring device arrangement was carried out by means of a modal confidence matrix.Through analysis and validation,it was determined that the selection of seven sets of equipment could complete the monitoring task and determine the optimal arrangement of points.Secondly,based on the integrated empirical mode decomposition method(EEMD),this thesis proposes a quadratic integrated empirical mode decomposition method based on orthogonality and correlation determination(OC-EEMD)for data preprocessing,and applies the quadratic method to solve the motion attitude angle of the flexible riser,and removes the gravitational acceleration component from the acceleration data,and calculates the riser three-way displacement by time domain integration.After that,the true value of the riser motion displacement is solved based on the multi-source data such as ship motion;finally,the feasibility and betterness of the algorithm are verified by setting up a calibration bench for the measurement of the tube motion.It is found that the displacement results and trends obtained by the above algorithm are close to the actual displacements,and the results obtained by the OC-EEMD method are found to be better than the EEMD method through error analysis.Finally,this thesis establishes the equivalent flexible riser finite element model according to the riser structure in actual engineering,and inputs the true value of the riser motion displacement obtained from the solution as the finite element displacement load condition to calculate and analyze the stress distribution and stress variation in time.Find the location of maximum fatigue damage accumulation by calculating the average value of stresses within the time course.The fatigue life of flexible risers was calculated using the rainflow counting method,linear damage theory and S-N curves.After calculation and analysis,the fatigue life of the inner tensile armor layer of the flexible riser analyzed in this thesis is 104.6450 years,and the life of the outer tensile armor layer is 198.2434 years.In this thesis,an optimized scheme of motion monitoring device arrangement is formed and a fatigue analysis technique of riser based on monitoring data is established.It is of great significance and adaptability to structural health monitoring and fatigue analysis in the field of marine engineering,and also has certain measurement reference value for related research in other fields.