摘要
绝大多数的钻具失效都是疲劳引起的。而交变应力集中是疲劳破坏的一个关键因素。因此定量分析研究钻具在井下所承受的应力水平及其分布规律 ,是研究钻具疲劳失效的一项重要内容。文章以固体力学有限元理论为基础 ,建立了带扶正器下部钻具组合在弯曲井眼或斜直井眼中的有限元力学模型 ,求解并得到了下部钻具组合的应力场。揭示了扶正器附近是应力集中区 ,而远离扶正器的两跨之间应力水平相对较低的应力分布规律。现场的资料分析也表明 ,正是扶正器或配合接头这些高应力水平的部位是最容易失效的部位 ;从钻具的结构上看 ,钻具连接螺纹正处在这些最大应力集中区 ,这是连接螺纹疲劳失效的根本原因 ,扶正器或配合接头的失效多发生在连接螺纹部位。文章的研究结果揭示了下部钻具组合失效的力学机理。
Fatigue usually results in performance failure of drilling tools. The concentration of alternate stress is a key factor of fatigue destruction. One of the most important project in studying on fatigue and failure of drill string is to quantitatively analyze the stress level and distribution rules of drill stem which is burdened at the bottom hole. Based on finite element theory of solid mechanics, finite element mechanics model is set up for BHA(bottom hole assembly) with centralizer in bending and slant borehole. Stress field of BHA can be obtained from solution. It is discovered that stress zones is gathered around the centralizer, while stress is relatively low on both two sides away from the centralizer. Field data analysis also shows that just because there is high possibility of failure around centralizer and those points of junction with high stress, the failure and fatigue in the jointing screw thread result from the screw threads situated in the parts with the highest stress. Most of the failure in centralizer and joints happens just around the jointing screw thread. The study concluder the methods and theory of failure in BHA.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2001年第5期46-48,共3页
Natural Gas Industry
基金
中国石油天然气集团公司"九五"科研项目 (项目编号 :部 140 )
关键词
石油钻井
钻具组合
钻柱稳定器
有限元
应力分布规律
Failure (mechanical)
Fatigue of materials
Finite element method
Mathematical models
Natural gas well drilling
Screw threads
Stress concentration
