西南石油大学学报(自然科学版)

• 石油机械工程及其他 • 上一篇    下一篇

钻柱表面裂纹在拉扭作用下的弹塑性断裂性能

赵广慧,汪浩瀚,石健,赵莉   

  1. 西南石油大学机电工程学院,四川成都610500
  • 出版日期:2014-06-01 发布日期:2014-06-01
  • 基金资助:

    国家自然科学基金重点项目“气体钻井技术基础研究”(51134004);国家自然科学基金青年项目“应力波作用下钻具表面三维裂纹的动
    态扩展研究”(11102173)。

Elastic-plastic Fracture Mechanics Analyses of Surface Cracks in
Drill String Subjected to Combined Loading

Zhao Guanghui, Wang Haohan, Shi Jian, Zhao Li   

  1. School of Mechanical Engineering,Southwest Petroleum University,Chengdu,Sichuan 610500,China
  • Online:2014-06-01 Published:2014-06-01

摘要:

在钻井作业过程中,井口附近钻杆受到的拉力和扭矩往往达到整个钻柱的最大值,尤其是在上提钻柱解卡、
震击解卡以及蹩钻、卡钻情况发生时,井口附近钻杆受力更为恶劣。针对井口附近钻杆的断裂问题,以某超深直井的
实际工况载荷为例,将钻杆外表面的缺陷简化为横向半椭圆裂纹,以30CrMo 作为钻杆材料并通过实验拟合得到其
Ramberg–Osgood(R–O)本构模型,研究了拉力和扭矩组合作用下裂纹的弹塑性断裂特性。得到钻进工况下钻柱外表
面裂纹扩展至不同深度的临界形状比以及塑性成分在J 积分中所占的比例;定量分析了拉力波动和扭矩波动对井口
附近钻杆弹塑性断裂性能的影响,发现扭矩波动对裂纹扩展的贡献远大于拉力波动,避免钻柱受到扭转冲击对延长钻
柱寿命有重要意义。

关键词: 钻柱, 半椭圆表面裂纹, J 积分, 弹塑性断裂, 有限元

Abstract:

Abstract:The drill pipe near the surface stands the largest tension and torsion in the whole drillstring especially during drill
pipe sticking or bit bouncing. As an example,a 5 inch drill pipe made of 30CrMo that was near the well head of an ultradeep
straight well was analyzed here. Simplifying the crack of the drill pipe as circumferential semi-elliptical surface crack
and using the fitted Ramberg-Osgood equation as constitutional relation,we simulated elastic-plastic fracture feature of the
drill string under combined loading of axial force and torsion corresponding to its drilling behavior. The transition aspect
ratios are determined for the given combined loading and the crack shape could be determined approximately corresponding to
different crack depths. The contribution of the plastic J-integral is estimated and the effect of material nonlinearity on the crack
propagation is described. Variations of J-integral as a function of axial force and torsional moment respectively are compared,
and the dangers from tension and torque fluctuation are evaluated quantitatively. Compared with tension,fluctuation in torque
contributes much more to crack propagation. It is an important significance for increasing drill string′s service life to avoid the
drill string from severe torsion impact.

Key words: Key words:drill string, semi-elliptical surface crack, J-integral, elastic-plastic fracture, finite element