钻柱与井壁碰撞的非线性有限元分析

根据连续介质力学和非线性有限元理论,给出了钻柱碰撞井壁过程中钻柱的控制方程,并建立了相应的有限元列式。采用显式时间积分方法求解了基于拉格朗日算法的碰撞动力学方程。计算实例与分析表明,钻柱与井壁碰撞时所造成的最大第一主应力达到308MPa,其结果远远大于人们的估计;碰撞是造成钻柱先期失效的首要原因。采用显式非线性有限元技术可以对钻柱与井壁碰撞的过程进行成功的数值仿真分析,钻柱与井壁碰撞的整个时间历程得以全面细致地模拟再现。

Nonlinear finite element analysis on drillstring colloiding with wellbore

Based on successive medium mechanics and theory of nonlinear finite element, equations are given for controlling the drillstring in the process of drillstring colliding with the wellbore and corresponding finite element equations are established. The collision dynamic equations based on Lagrangial algorithm are solved by using explicit integration equation. The calculation example and its analysis show that the first maximum major stress induced in the collision is as high as 308 MPa, which is much higher than the estimated value. Collision is the major reason of premature drillstring failure. A successful numerical simulation can be conducted on the collision by using the technique of explicit nonlinear finite element analysis, by which the whole process of the collision is revealed delicately and comprehensively.