深水环境下隔水管的横向自由振动分析

Study on lateral nature vibration of marine riser under deep water

隔水管是海洋钻井工程中的必要设备。在深水环境下,隔水管的疲劳失效问题普遍存在,隔水管的强烈振动是导致其失效的主要原因之一。本文采用微元法,得到了隔水管在各种载荷作用下的横向振动规律及其横向振动的固有频率的分布规律,进一步分析了各种因素对隔水管横向振动固有频率的影响。结果表明:隔水管的长度增加时,固有频率减小;随着顶部张力比的增加,隔水管的横向振动的固有频率也增加;随着壁厚的增加,隔水管横向振动的固有频率逐渐降低;而随着钻井液密度的增加,隔水管横向振动的固有频率增加;海水的存在使隔水管的横向振动固有频率降低。该研究有利于避免隔水管在使用过程中出现强烈的共振现象,为减小隔水管的失效提供了理论依据。

Marine riser has become necessary equipments during ocean drilling.With the increase of the water depth,the failure of marine riser is a common phenomenon.Among many reasons that may cause marine riser failure,strong vibration of marine riser is one of the main reasons.The rules of lateral vibration of marine riser under various loads are studied according to the actual situation by using micro element method.Influence of various factors that affect the frequency of lateral vibration of marine riser is considered and the rule of frequency distribution of lateral vibration is obtained.Results obtained indicate that the natural frequency decreases with the length of marine riser increase;the natural frequency increases with the top tension of marine riser increase;with the wall thickness of marine riser increase,the natural frequency of transverse vibration decreases;with the increase of the density of drilling fluid,the natural frequency of lateral vibration of marine riser increases;seawater makes the natural frequency of transverse vibration of the riser become lower.These results are helpful to avoid the phenomena of resonance of marine riser,they also can provide theoretical basis for avoiding marine riser failure.