Reliability Analysis And Optimization Design Of Umbilical Cable Structure In Subsea Production System

Umbilical cable is one of the key control equipments in subsea production system,of which the performance directly affects the safe operation of the whole system.So,it is necessary to carry out the reasonable design and accurate analysis of the umbilical cable for meeting the safe requirements.The current design of umbilical cable is based on the safety factor without considering the influence of random factors.Concerning the importance of umbilical and the particularity of application environment,it is unreasonable to ignore the uncertainty.Therefore,the reliability analysis is introduced into the umbilical cable design.The reliability analysis and optimization design method of umbilical cable are presented in detail in this paper.The research works of this paper have the important reference value in the design of cross section and global configuration of umbilical cable.The section design of umbilical cable is the primary content which directly determines the physical and mechanical properties.Considering the uncertainty of steel tube size and material,the strength reliability of cross section at the top of configuration is analyzed.If the design dose not match the reliability index,the reliability optimization model of umbilical sectional strength is established which takes the reliability index as the constraint.According to the optimization results,it is found that the reliability design of umbilical is more security and economical compared to the deterministic design.Aimed at the limitations of the extreme value analysis of global configuration,the surrogate model is adopted to establish an approximate model of the extreme value of tension and minimum bending radius about the direction of ocean wave,current and floater position.The mathematical model is of high precision and minor calculation amount replacing the original nonlinear finite element model.Based on this model,the reliability analysis of extreme value is performed considering the random distribution of input variables.The existing design of global configuration have some disadvantages such as large number of parameters,various combination cases and lacking of guidelines.Through the previous reliability analysis methodology of the configuration,the optimization model with the objective of minimum length of the whole configuration is established,the extreme value reliability is treated as the constraint to find the proper parameters of configuration.Finally,the reliability analysis and optimization methods are applied to the umbilical cable in some oil field,which is supported by National High Technology Research and Development Program of China(863).The results verify the advantages and effectiveness of these methods compared with the traditional methods.