Integrated Analysis Of Deepwater SCR And Floating Platform

In recent years,offshore oil and gas activities move to deeper oceans, various innovative production facility and new technology are proposed to meet severe deep-water environments. Steel Catenary Risers (SCR) have become to a preferred choice for oil export from floating production system to shore for unique advantages. SCR will bear the hydrodynamic loading during service,and it also be effected by floating motion and submarine groove, which result in a more complex dynamic response. So study on the influence mechanism of floating body on SCR and dynamic characteristics of SCR is of great practical significance and application value.A flexible cable model based on the assumption of large deformation in bending and a dynamic analysis program cable3D developed by Chen are introduced in this paper. Flexible cable model which allow large deflection can simulate the interaction of SCR and seabed and location change of Touch Down Point (TDP).This model is suitable for longer element,it is also of quick convergence and calculation accuracy.The integrated model of SCR and floating platform on the basis of flexible cable model is proposed in this thesis, and the original code cable3D is improved. In this integrated model,floating platform and SCR are analyzed as a whole, the platform is modeled as a rigid with elastic constraints of mooring lines and resilience in still water. The motion equation of the rigid structure is transferred to suspension point of SCR according to transform, then it is combined with the motion equation of SCR. Additional mass and damping force of floating platform are taken into account. This integrated model is compared with decoupling algorithms, the result shows that the integrated model factually reflects dynamic effects between SCR and floating platform,By use of the elastic foundation beam model, the interaction between SCR and seabed is studied in this paper. The finite element equation of elastic foundation beam model is derived according to the minimum potential energy principle, and numerical analysis in time domain is conducted based on finite element method. The dynamic responses of TDP are computed comparing spring model. The results show that elastic foundation beam model has low sensitivity to element length and is suitable for longer element. This method can improve computation efficiency and attain a higher precision.