钻头处的边界条件研究

STUDY ON THE BIT BOUNDARY CONDITION

多年来，在下部钻具组合计算的边界条件中，人们都假设钻头与地层之间的弯矩为零，钻头看作铰支。由于许多教科书和文献中提到钻头处某些极个别时刻存在弯矩，有些国内研究者便否定以前的假设，即将钻头处看作固定支。文中通过对钻井机理的探讨，分析了原来假设观点正确的原因，并通过受力分析给出了铰支假设下钻头处的边界条件。

In mechanical analysis of the bottom hole assembly, the boundary condition at the bit has been taken as an articulated support, i. e., the bending moment between bit and formation is zero degree.Some experts at home deny the suppose and look the bit as an immovable support. By discussing the drilling mechanism, the paper analyzes the original suppose and supports it, and also presents the boundary condition at the bit in the suppose that the bit is looked as an articulated support.