天然气勘探与开发2025，Vol.48Issue(4)：70-79,10.DOI:10.12055/gaskk.issn.1673-3177.2025.04.007
大尺寸井眼钻铤断裂原因分析及钻具安全管理措施
Causes of drill collar failure in large-diameter boreholes and drilling tool safety management measures
摘要
Abstract
In order to reduce the failure rate of drilling tool in large-diameter boreholes in the Sichuan-Chongqing area,the service history of drill collar was reviewed with the failure accident of ⌀228.6 mm drill collar while tripping out of the large-diameter borehole (⌀406.4 mm) of Well Z201-A as an example. In addition,the fracture-surface characteristics,drill string mechanical simulation and downhole vibration strength were analyzed. Accordingly,the causes of the failure were determined,and the drilling tool safety management measures were proposed. Research results are shown as follows:(i) The case drill collar failed due to fatigue,caused by weakened drill collar strength,complex loading on the drilling tool,and intense downhole vibration. (ii) After being used many times,the outer diameter of the drill collar is reduced from 228.6 mm to 226.0 mm,and the box-to-pin thread bending strength ratio (BSR) is 2.18,lower than the API standard value of 2.5. The weakening strength of box thread is one of the reasons for the failure. (iii) Mechanical simulations of the drill string reveal higher bending moments and stresses in large-diameter boreholes compared to small ones. The weak point of the bottom hole assembly (BHA) is adjacent to the centralizer,exhibiting the accelerated fatigue,which is the main reason for the failure. As the result,the broken drill collar is right above the centralizer. (iv) The surface strata where the largediameter borehole (⌀660.4 mm) of the first spudding in Well Z201-A drilled into have alternate soft and hard lithologies. The wellhead torque measurements suggest intense downhole vibration with peak lateral vibration exceeding 30 g,which brings extreme damage to the thread. The downhole vibration calculation results indicate that the larger the borehole diameter,the greater the average equivalent stress of drilling tool,and for the borehole with diameter above ⌀444.5 mm,the average equivalent stress increases exponentially. Compared with the weight on bit (WOB) fluctuation,the torque fluctuation has greater influence on the stress amplitude of drilling tool. (v) Based on the above findings,the specific measures for drilling tool safety management are proposed from two aspects,i.e.,drilling technology and drilling tool management. It is concluded that the findings provide guidance for the safety of drilling tool in large-diameter boreholes,which is beneficial for reducing drilling tool accident rate,shortening drilling cycle,controlling costs,ensuring optimal and fast drilling,and improving quality and efficiency.关键词
大尺寸井眼/钻具事故/疲劳断裂/振动强度/弯曲强度比/应力幅/钻具安全管理/川渝地区Key words
Large-diameter borehole/Drilling tool accident/Fatigue failure/Vibration intensity/Bending strength ratio/Stress amplitude/Drilling tool safety management/Sichuan-Chongqing area分类
能源科技引用本文复制引用
蔡明杰,戴巍,黄忠,陈友生,刘艳彬,李明阳,李昱垚..大尺寸井眼钻铤断裂原因分析及钻具安全管理措施[J].天然气勘探与开发,2025,48(4):70-79,10.基金项目
中国石油集团川庆钻探工程有限公司科技项目"万米特深井大井眼钻柱安全分析与优化技术研究"(编号:CQ2023B-57-1-3). （编号:CQ2023B-57-1-3）
