测井技术2025，Vol.49Issue(4)：510-518,556,10.DOI:10.16489/j.issn.1004-1338.2025.04.003
基于目标场法的核磁共振测井仪射频线圈设计方法
Target Field Method for NMR Logging Tool RF Coil Design
摘要
Abstract
To improve the detection performance of nuclear magnetic resonance(NMR)logging tools in narrow borehole environments and optimize the power consumption and signal to noise ratio(SNR)of radio frequency(RF)coils,a design method for RF coils based on the target field method was adopted.The target RF magnetic field distribution was set based on the orthogonal matching conditions between the external stray static magnetic field and the RF magnetic field.The numerical response equation between coil current density and the target magnetic field was constructed via the target field method.The objective function was solved using Tikhonov regularization and minimum energy dissipation to invert the optimal coil structure,which was then compared with saddle-shaped coils through finite element simulation and physical tests.The results show that:①In physical tests,the optimized coil has lower optimal pulse energy and better SNR than the saddle-shaped coil(13.8 vs 8.8)with a higher first wave amplitude(145 vs 130);②Simulation results indicate that the SNR of the optimized coil is 5%higher than that of the saddle-shaped coil,with better magnetic field uniformity;③The quality factor of the optimized coil(82)is higher than that of the saddle-shaped coil(64),with higher emission efficiency;④This method can be applied to the design of other cylindrical coils,such as unilateral cylindrical coils for wireline NMR instruments and solenoidal coils for logging-while-drilling NMR instruments.It is concluded that the target field method is feasible for the design of RF coils for NMR logging tools,can significantly improve the detection performance of the instruments(e.g.,emission efficiency,SNR),provides greater freedom for coil design,and facilitates instrument optimization.关键词
核磁共振测井/射频线圈/目标场法/信噪比/Tikhonov正则化/有限元仿真/柱面线圈/发射效率Key words
nuclear magnetic resonance logging/radio frequency coil/target field method/signal-to-noise ratio/Tikhonov regularization/finite element simulation/cylindrical coil/emission efficiency分类
数理科学引用本文复制引用
龙志豪,李新,于慧俊,汪正垛,肖立志,罗嗣慧..基于目标场法的核磁共振测井仪射频线圈设计方法[J].测井技术,2025,49(4):510-518,556,10.基金项目
国家自然科学基金项目"方位扫描核磁共振探测新方法与实验验证"(42204106) （42204106）
中国石油大学(北京)学科前沿交叉探索专项"万米深地随钻测井探测器关键技术研究"(2462024XKQY009) （北京）
