中文摘要：

钻杆是钻井过程中易受破坏的关键部件,在其服役过程中进行检测,对于减少钻具失效事故具有重要意义。针对钻杆在役检测的特点,提出一种新型外穿式交流电磁场检测方法,建立针对钻杆外表面轴向裂纹的外穿式交流电磁场检测有限元仿真模型,分析钻杆表面感应电磁场分布以及裂纹引起的电磁场畸变信号与裂纹尺寸关系,在此基础上提取裂纹识别特征信号,基于仿真模型分析激励线圈提离高度影响,设计开发井口钻杆外表面轴向裂纹在役检测系统,并进行试验测试,仿真和试验结果表明：外穿式交流电磁场检测探头所提取的钻杆轴向裂纹特征信号Bx和Bz分别反映裂纹深度和长度,具有定量识别能力;激励线圈提离高度可满足在役检测需要;外穿式交流电磁场检测系统利用周向阵列检测线圈可有效检测钻杆表面轴向裂纹。

英文摘要：

Drill pipe is a critical and vulnerable component in oil gas industry. A novel feed-through alternating current field measurement（ACFM） is proposed to achieve in-service detection for axial cracks on the surface of drill pipe. The finite element model is built by ANSYS software for analyzing the induced electromagnetic field distribution and disturbance caused by the axial crack on the external surface of drill pipe. Signal features of the crack are extracted through quantitatively analyzing the relationship between the size of crack and disturbance field. On the basis of theory and FEM simulation, the feed-through ACFM system is set up and proved by the axial crack of drill pipe detection experiments. The results show that, the signal features of Bx and Bz from the feed-through ACFM system show the depth and length information of the axial crack respectively on pipe string, and the lift-off effect can meet the demands of in-service detection for drill pipe. Furthermore, the feed-through ACFM system with sensors array can detect all the axial cracks in-service with a single pass scanning.