Study On Multibody Dynamic Characteristics Of Deepwater Drilling Riser System

Riser system is an important part of connecting platform and subsea wellhead.In practice,there will be obvious relative movement between riser,expansion joint,tensioner and platform.The whole deepwater drilling platform-tensioner-riser system is a typical multibody system,which is called deepwater drilling riser multibody system in this paper.At present,most of the researches take riser system as the research object,and the interaction between the components of the riser system in deepwater drilling is not considered.The accuracy of the dynamic analysis of the riser system needs to be improved.In this paper,the dynamic characteristics of deepwater drilling riser are studied based on the project of "Research on deepwater drilling riser multibody system dynamics and recoil control" supported by National Natural Science Foundation of China.The research results are as follows:The coupling relationship among the components of deepwater drilling riser multibody system is clarified,and the theoretical models of direct acting tensioner,riser system and other accessories are established respectively.The dynamic model of deepwater drilling riser multibody system is established by fully considering the coupling relationship and boundary conditions among platform,tensioner system and riser system.On this basis,the multibody system dynamics simulation model of deepwater drilling riser is established by using Matlab/Simulink,and the tensioner and riser system models of the multibody system dynamics simulation model are tested based on commercial software.The results show that the model of the key components in the multibody system dynamics simulation model is reliable,which provides a basic simulation model for the follow-up study on the multibody dynamic characteristics of deepwater drilling riser system.Based on the established multibody system dynamics simulation model of deepwater drilling riser,the dynamic characteristics of deepwater drilling riser multibody system under different work conditions are analyzed.The results show that the tensioner system can provide the opposite force with the riser offset direction under the connection condition,thus restrain the displacement of the riser system and reduce the bending moment of the riser system.At the same time,the tensioner system can reduce the transmission of the heave of the platform.The bending moment amplitude of riser system decreases with the increase of platform sway period and the lateral displacement of riser system is relatively large when there is tensioner in a large range.Under the emergency disconnected condition,the peak value of the riser system rebound increases with the increase of the platform heave amplitude and decreases with the increase of platform heave period.The damping effect of hydraulic system in the tensioner system can make the disconnected riser system enter the stable stage faster;under the soft suspension mode,the axial amplitude of the riser system increases with the increase of the platform heave amplitude.The change trend of the transverse displacement envelope of the riser system is different from that under the connection condition,and the change trend of the bending moment envelope is basically the same as that under the connection condition.