基于微凸体接触的钻柱纵向振动减摩阻

摘要

Based on asperity contact deformation theory, an analysis and calculation model of the friction between drill-string and wellbore rock was established, and the mechanism of friction reduction via exciting drill-string vibration longitudinally was studied. The results show that the criteria for friction reduction by vibrating drill-string longitudinally is that the relative sliding velocity of the drill-string on the wellbore rock should be less than the amplitude of the velocity of drill-string vibra-tion. The friction reduction effect increases with the increase of the vibration frequency, and it increases firstly with the vibra-tion amplitude then decreases, and there is an optimal amplitude. The friction reduction effect decreases with the increase of the drill-string movement velocity, the penetration depth of the asperity and the friction coefficient. The results of orthogonal testing indicate that the influence on friction reduction of vibration frequency, amplitude, penetration depth of the asperity, friction coefficient and the velocity of drill-string weakens in sequence, of which the vibration frequency, amplitude, and the penetration depth of the asperity are the most significant factors.%基于微凸体接触变形理论，建立钻柱纵向振动条件下钻柱与岩石间摩擦力的分析计算模型，探索钻柱纵向振动减摩阻规律。结果表明：钻柱纵向振动减摩阻的条件是钻柱相对于岩石运动速度小于钻柱纵振速度幅值，且振动减阻效果随振动频率的增大而增强，随振幅的增大呈现先增强后减弱的趋势，存在最优振幅，而随着钻柱与岩石间相对运动速度、相对法向压入量和摩擦系数的增大，振动减摩阻效果趋于弱化；钻柱振动频率、振幅、相对法向压入量、摩擦系数和钻柱与岩石间相对运动速度对振动减阻的影响作用依次降低，其中振动频率、振幅和相对法向压入量为显著因子。