关键词: 底部钻柱, 动力学, 运动状态, 钻压, 转速, 实验研究

Abstract: According to the principle of similitude, an experimental device for investigating the motion behaviors of bottom drill string was designed and set up. Some experiments have been done by means of the device under different weights on bit and rotary speeds. The result shows that the bottom drill string exhibits three kinds of motion states at different rotary speeds and a certain weight on bit, including regulax swaying, irregular swaying and regular whirling. With the increase in rotary speed, the motion state of drill string will be successively transformed from regular swaying into irregular swaying and regular whirling. The weight on bit and rotary speed are the main factors affecting the motion behavior of drill string. The higher the rotary speed is, the more easily the regular whirling will be formed. And increasing weight on bit can prevent irregular swaying and regular whirling from appearance at the bottom drill string. The analysis on experimental result shows that there is an optimum match between weight on bit and rotary speed to prevent hole inclination.

Key words: bottom drill string, dynamics, motion state, weight on bit, rotary speed, experimental study