Research On Integrity Management Technology For Deepwater Riser

This dissertation is supported by the National Major Science and Technology Project “Whole Life Integrity Technology and Engineering Application of Deepwater Riser-subsea Wellhead”(Subject number: 2016ZX05028001-005).The research on integrity management technology for riser is conducted.Taking fatigue and corrosion defects as research objects,the research on damage and reliability for deepwater riser is conducted,the maintenance optimization strategy for deepwater riser is established,and these work provides scientific basis for the riser integrity management to achieve the purpose of preventing the riser from failing.The research results mainly include:(1)Assessment of fatigue damage of riser system based on monitoring dataThe method of dynamic reconstruction and fatigue damage assessment of riser system based on monitoring data is studied.The excitation modes of riser system are identified based on an energy-based method.The dynamic response of riser system is reconstructed through weighted waveform analysis(WWA).On the basis of these work,The fatigue damage of riser system is calculated based on S-N curve method.The fatigue hot spots and fatigue stress of riser system are identified.These studies lay the foundation for the study of the subsequent riser integrity management.(2)Assessment of dynamic fatigue reliability of riser based on bayesian networkUsing riser strain monitoring data as the source of stress,the riser crack propagation model is established based on fracture mechanics.Considering the randomness of variables in the crack propagation model,the crack propagation and reliability prediction model is established based on bayesian network.The analysis of bayesian network forward reasoning is conducted based on random variable distribution,and the crack depth probability distribution and reliability index with service time are identified.The analysis of bayesian network reverse reasoning is conducted through adding detection results,and the influence of detection results on riser fatigue random parameters is identified.(3)Research on maintenance optimization of riser based on bayesian networkThe riser maintenance optimization model is established.The riser maintenance optimization process is established based on event tree.The genetic algorithm(GA)in MATLAB is used as the optimization algorithm,and the crack propagation bayesian model is established through the bayesian toolbox(BNT)in MATLAB.The riser reliability model during maintenance optimization process is established based on bayesian update.The search algorithm and process of riser maintenance optimization is proposed through the integration of GA and bayesian network.The riser maintenance optimization is run and the results are verified by enumeration method.The results show that,the proposed riser maintenance optimization algorithm can solve the maintenance optimization search problem accurately and efficiently.(4)Research on maintenance optimization of riser based on influence diagram modelIn order to solve the problem of separate iterations of reliability calculation and detection time search,and to consider the incomplete repair,multi-failure modes coupling and other issues,the influence diagram method for riser maintenance optimization is proposed.The riser maintenance optimization influence diagram model is established,the riser maintenance optimization and reliability update are conducted.The maintenance optimization in the case of incomplete repair and multi-riser are conducted.Taking fatigue and corrosion failure as an example,the maintenance optimization in the case of multi-failure modes coupling is conducted.