Study On Dynamic Coupling Behavior Of Top Tension Riser For Deep-water Tension Leg Platform

Because there is no dependable technology of tension leg platform(TLP)and top tension risers(TTR)in our country,the dynamic analysis of TLP and TTR should be developed to meet the demand of the first TLP in South China Sea.The paper is supported by the project of CNOOC named “Research for drilling and completion safe opration technology of riser system for TLP”,By taking the TLP which will operate in South China Sea as subject investigated,the hydrodynamic characteristics of TLP,dynamic response and impact effect of cluster risers system are analyzed.In order to recognize the variation of interation between the factors and dynamic response of cluster risers,sensitivity analysis is carried out by using orthogonal test and variance analysis.Hydrodynamic characteristic of TLP is analyzed by combining frequency domain analysis and time domain analysis based on three dimensional potential flow theory used AQWA,the RAOs and time domain motion of TLP and dynamic tension of tendons can be received.Taking account of the movement of TLP,blackout effect,conductor-soil interaction and drag effect,dynamic characteristics of cluster risers is gained under monsoon,typhoon or interwave,the impact mechanism of cluster risers under extreme conditions is analyzed,and coupling analytical procedure of cluster risers is established.Finaly orthogonal test is constructed based on those techononlgy,the sensitivity between risers' factors and dynamic characteristic is studied,and main factors which are gained to support control measures.Results show that while the increase of wave height aggravates the motion of TLP.The displacements of TLP in different directions have no significant changes,because of axial symmetry.The max effective stress of risers has no apparent mutation under operational condition by analyzing the cluster risers.The stress concentration is located near to the tension ring and under taper stress joint.Under extreme condition,the effective stress increases obviously,the max stress is 400 MPa,and impact effect occure under 100-year typhoon.Through sensitivity analysis,results show that the displacement of TLP and current are most important factors to effective and bending stress,the current and space between two risers are major factors to impact effect.