Multi-body Dynamic Analysis And Application Research On Deepwater Drilling Riser System

Deepwater drilling riser is a key component connecting the platform and the sea floor,the top of the riser system is connected to the platform via expansion joints,tensioners,and flexible joints.Under the circumstance of marine environmental load,there are obvious relative movements among various components.Deepwater drilling riser-telescopic joint-tensioner-platform is a typical multi-body system,which is referred to as deepwater drilling riser multi-body system for short.Under the combined effects of marine environmental loads and operational loads,the risk of failure of risers,telescopic joint,and excessive tensioner strokes in multi-body systems of risers is a weak link in offshore oil and gas exploration and development.In view of this,this article combines the subproject of 973 project“Coupling characterization and safety analysis of the dynamics of deepwater subsea wellhead-riser-platform system”is applied to study the multi-body system of deepwater drilling riser and the multibody dynamics of the riser system under different working conditions.The multi-body dynamics characteristics and the reliability of the riser system under extreme sea conditions have made great progress,which can provide support for the multi-body dynamics analysis,design and safe operation of the deepwater drilling riser system.The main research progress of this article is summarized as follows:1 Multi-body dynamics model of riser systemAnalyze the kinematic basis of the multi-body system,perform discrete variational derivation based on the Lagrangian equation,and finally give a multi-body dynamics theoretical model of the riser system.Among them,the riser and the tensioner are analyzed separately and a theoretical model is established.Based on this,combined with multi-body dynamics modeling and simulation software ANSYS,a multi-body modeling and multi-body model assembly method for the riser system is presented.2 Multi-body dynamics characteristics of riser systemBased on the multi-body dynamics simulation model of the multi-body system of a riser,the multi-body dynamics characteristics of the riser system during the entire work process of connection-backlash-suspension are simulated and analyzed.Analyze the dynamic response law of the multi-body system of the riser under current,platform swing,wave and platform heave under the connection condition,compare the dynamic response results with and without the tensioner model,and determine whether there is any influence of the tensioner.Analyze the axial response of the top and bottom of the riser in breakaway moment,the lateral response of each node on the riser,and the axial response of the tensioners in different directions to determine the law of the recoil response of the riser system.Analyze and study the multi-body dynamic response law of the riser system under different suspension conditions.3 Multi-body dynamic parameter sensitivity analysis of riser systemBased on the multi-body dynamics analysis model of deepwater drilling riser system,the orthogonal test method was used to extract the test results for range and variance analysis,and the key dynamic influencing factors of the riser system under different working conditions of connection-recoil-suspension were determined.The maximum von mises and maximum transverse deformation results are extracted under the connection and suspension conditions.The maximum von mises in the first cycle of springback and the maximum axial displacement results at the top and bottom of the riser at the rebound peak under recoil conditions.4 Reliability Analysis of Working Strength of Risers Multibody SystemBased on the probability distribution of wave height and current velocity in the operating sea state,Monte Carlo method and response surface method are used to analyze the operational reliability of the riser system,and the maximum von mises values for a series of different wave heights and different ocean current velocities are obtained.In the above,the strength failure response surface of the riser composed of two random variables is established,and the Monte Carlo method is used to generate 10~6 random numbers to calculate the strength failure probability and reliability of the riser system.