钻柱与井壁碰撞的拉格朗日算法动力学仿真

在影响钻柱横向振动的诸多因素中，钻柱与井壁的碰撞起着首要的作用。根据连续介质力学和非线性有限元理论，给出钻柱碰撞井壁过程中钻柱的控制方程，并建立相应的有限元列式。采用显式时间积分方法求解基于拉格朗日算法的碰撞动力学方程。数值计算的结果较真实反映钻柱碰撞井壁的动态过程，并与前人的试验结果吻合良好。研究结果表明，在文中的算例情况下，钻柱与井壁碰撞所造的最大第一主应力达到308MPa，其结果远大于人们的估计；碰撞是造成钻柱先期失效的首要原因。该分析方法有效，可用于对钻柱动力学进行进一步的研究。采用显式非线性有限元技术可以对钻柱与井壁碰过程进行数值仿真分析，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。

CONTACT-IMPACT DYNAMIC SIMULATION OF DRILLSTRING AND FORMATION BASED ON LAGRANGIAL ELEMEMT METHOD

In the most causations affecting drilling transverse vibration,contact-impact of drillstring and formation was the most important.Based on the continuous mechanics and nonlinear finite element method, several control equations about contact-impact of drillstring and formation were established, and the dynamic finite element formulations and discretionary for contact-impact of drillstring and formation were given. The contact-impact dynamic equations based on lagrangial method were solved using explicit integration. The numerical results of the contact-impact can reflect the dynamic process of contact-impact really and agree with the prevenient experiment well. The results show that: in the condition of this article the first principal stress of the drillstring can reach to 308 MPa, the result is beyond the normal estimate; contact-impact is the principal surce of drill premature failure; this method is useful and suitable for the future drillstring dynamic research. Using explicit integration and nonlinear finite element can simulate the collision between the drillstring and formation successfully, the process of the collision between the drllstring and formation can be revealed compressively and delicately.