确定底部钻具组合上切点位置的新观点

NEW CONCEPT FOR DETERMINING THE TOP TANGENTIAL POINT ON BHA

在计算底部钻具组合的受力和变形时 ,以前一般都是按弯矩为零的条件来确定其上切点的位置。提出了一种新观点 ,即按照钻柱与井壁的接触力为零的条件来确定这一位置。推导了相应的计算公式 ,给出了算例 ,并通过算例的结果证明了该观点的合理性。

The tangency point of Bottom Hole Assembly is located at where the drill string just touches the wall of the borehole, and the contact force is zero here.Therefore, the method to determine the position of tangency point should be based on this condition instead of the traditional one which requires the moment is zero here.The formula of this new method was deduced , the different results of the two methods were shown through examples, the rationality of the new method was proved by the result of the examples.