Dynamic Response Analysis Of Deepwater Lazy-wave SCR

Lazy-wave SCR can effectively reduce the top tension of the riser and the burden of the floating platform.And it also can improve the dynamic response of the TDP to a certain extent and alleviate the fatigue damage in this area by virtue of the special structural form which makes it to be an effective retrofit design of traditional SCR in ultra-deep water applications.In this paper,the dynamic response analysis is carried out with the lazy-wave SCR as the research object and the numerical simulation is carried out based on the relevant theory.Firstly,the dynamic response analysis of lazy-wave SCR and traditional SCR is carried out based on the nonlinear seabed soil model by taking the riser-soil interaction as the research focus.An uncoupled model of the vessel and two kinds of risers is established by using Orca Flex.The parameter sensitivity analysis of lazy-wave SCR and the comparison with the traditional simple SCR which is under the same working conditions are carried out.The results show that lazy-wave SCR can effectively suppress the development of the submarine trench and improve the dynamic response of the TDZ.Secondly,on the basis of uncoupled analysis,the lazy-wave SCR which has the optimal dynamic performance and a traditional SCR are selected to make the coupled dynamic analysis with a TLP.In this research,when the incident directions of environmental loads are different,the dynamic response differences of this two kinds of risers are studied,and the results of the platform displacement,the configuration of this two kinds of risers and the distribution of bending moment are analyzed.The results show that under the different working conditions,the influence of lazy-wave SCR on the platform motion is smaller than traditional SCR.Although the lateral deflection,the bending moment and the maximum stress of lazy-wave SCR are larger than traditional SCR,the top tension level is lower,and the dynamic change amplitude of the bending moment and the maximum stress of the TDP as well as the number of stress cycles are significantly reduced,which makes the dynamic response and fatigue performance of the TDZ are effectively improved.The research of this paper highlight the superior performance of the modified design of lazy-wave SCR,and realize the coupled analysis with the floating platform,which provides reference and research basis for the application of this kind of riser in the development of offshore oil and gas in China.