摘要
为了降低川渝地区大尺寸井眼钻井过程中的钻具事故率,以Z201-A井大尺寸井眼(φ406.4 mm)起钻中φ228.6 mm钻铤断裂事故为例,回溯钻铤使用历程,并从钻铤断面特征、钻柱力学模拟和井下振动强度等方面加以分析,确定了断裂原因,进而提出了钻具安全管理措施。研究结果表明:①该钻铤为疲劳断裂,具体原因包括钻铤强度减弱、钻具受力复杂及井下振动剧烈等;②该钻铤经多次使用,外径已由228.6 mm磨损至226.0 mm,母螺纹和公螺纹的弯曲强度比为2.18,低于API标准值(2.5),母螺纹强度减弱是钻铤断裂的原因之一;③钻柱力学模拟结果表明,较之于小尺寸井眼,大尺寸井眼钻进过程中钻具承受了更大的弯矩和应力,扶正器附近位置是钻具组合受力薄弱点,疲劳速度更快,断裂的钻铤正是位于扶正器上方,其为断裂发生的主要原因;④该井第一次开钻大尺寸井眼(φ660.4 mm)表层钻进时,岩性软硬交错,井口扭矩测量表明井下振动剧烈,最高横向振动强度超过30 g,对钻具螺纹的损伤极大,同时井下振动计算结果表明,井眼尺寸越大,钻具平均等效应力越高,井眼尺寸超过φ444.5 mm后,钻具平均等效应力呈指数级上升,并且较之于钻压波动,扭矩波动对钻具应力幅的影响更大;⑤基于上述原因,从钻井技术、钻具管理两个方面提出了钻具安全管理的具体措施。结论认为,该项研究成果可以为该区大尺寸井眼钻井中的钻具安全提供指导,有助于降低钻具事故率、缩短钻井周期、控制钻井成本、保障优快钻井、实现提质增效。
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 ofφ228.6 mm drill collar while tripping out of the large-diameter borehole(φ406.4 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 large-diameter borehole(φ660.4 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 aboveφ444.5 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.
作者
蔡明杰
戴巍
黄忠
陈友生
刘艳彬
李明阳
李昱垚
CAI Mingjie;DAI Wei;HUANG Zhong;CHEN Yousheng;LIU Yanbin;LI Mingyang;LI Yuyao(CNPC Chuanqing Drilling Engineering Company Limited,Chengdu,Sichuan 610051,China)
出处
《天然气勘探与开发》
2025年第4期70-79,共10页
Natural Gas Exploration and Development
基金
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)。
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
Large-diameter borehole
Drilling tool accident
Fatigue failure
Vibration intensity
Bending strength ratio
Stress amplitude
Drilling tool safety management
Sichuan-Chongqing area
