基于材料滞后效应的钻具旋转状态分析

Drill Tool Rotation Analysis Based on Lag Effect of Material

为了确定钻具在井下的旋转方式以及不同旋转方式之间的转换规律,分析了钻柱材料滞后效应、钻柱弯曲挠度、转盘转速以及钻柱与井壁间摩擦系数和滚动摩阻系数对钻柱旋转方式的影响。通过研究发现,钻柱的弯曲和滞后效应是引起钻柱公转和偏磨的主要原因,钻压小于钻柱临界钻压的情况下,钻柱不会出现公转和偏磨现象;中和点上方6.5个无因次单位长度以下的钻柱才存在公转、自转和涡动3种旋转形式,特定的钻井参数条件下,滞后效应会导致钻柱在不同旋转方式之间频繁转换,从而影响钻柱安全;上部钻柱只存在涡动和自转2种稳定的旋转状态,不会出现公转和偏磨现象,偏磨后的钻杆可在上部使用。

In order to determine the rotation mode and the transition between different rotation modes of drill string,the lag effect of drill string material,drill string bending deflection,rotary speed,the friction coefficient and rolling friction between drill string and the wall affecting the rotation of drill string was analyzed.Rotating mechanical model of bottom hole assembly was established for discussing and describing kinetic mechanism and rotation law of drill string.Critical condition of the drill string rotation mode is obtained.Lag effect is internal cause of drill string eccentric wear.The results show that in the condition of particular drilling parameters,the rotation mode of drill string are changed frequently,and the safety drilling is affected.