钻柱纵向振动分析与应用

利用钻柱纵向振动数学模型，分析了钻柱轴向应力振幅分布曲线和钻柱中最大轴向应力幅频曲线的特征以及钻井液粘度、激励位移、减振器位置对钻杆中最大轴向应力振幅的影响。分析表明：钻柱中轴向应力振幅沿纵向呈波状分布，其最大值在钻柱底部或钻杆中；钻杆中的最大轴向应力振幅随转速的变化曲线呈凹坑形，为了保护钻柱，应该选择凹坑中间的转速带；钻杆中的最大轴向应力振幅和钻柱底部的轴向应力振幅随转速的变化趋势并不完全一致，以后者作为判断钻柱是否共振和优选转速的指标不够准确，而应以前者作为该指标；钻杆中的最大轴向应力振幅与激励位移大致成正比；钻井液粘度越高，钻杆中的最大轴向应力振幅越小；减振器位置可以改变钻柱纵振系统的固有频率，从保护钻柱角度考虑，低转速时，减振器应紧靠钻头安装，高转速时，减振器应与钻头保持一定距离；通过优选钻具组合和转速，防止钻柱共振是预防钻具失效的有效措施

Analysis on longitudinal vibration of drill string and the corresponding application

Using the mathematical model of longitudinal vibration of drill string,the characteristics of the axial stress amplitude distribution curve and the maximum axial stress amplitude-frequency curve for drill string were analysed.The impacts of drilling fluid viscosity,bit displacement and shock absorber's installation position on the maximum axial stress amplitude in drill pipe were investigated.The analysis shows that: the axial stress amplitude along the drill string is wavelike distributed and the point of ...