MRIL-P型核磁共振测井仪探头磁场数值模拟

Numerical Simulation of Magnetic Field Distribution for MRIL-P Logging Tool Sonde

核磁共振测井仪的静磁场和射频磁场分布决定了仪器的测量频率、探测区域和探测深度、磁场梯度、信号强度等参数。推导出了核磁共振测井仪器磁场的数学物理模型。以居中型核磁共振测井仪MRIL-P探头为例,建立核磁共振测井仪探头结构模型,利用有限元法模拟探头静磁场和射频磁场的分布。认为在探测区域内其静磁场为梯度磁场。研究静磁场和射频磁场的分布特性和匹配关系,通过优化天线结构使射频磁场和静磁场匹配。利用三维磁场扫描对静磁场数值模拟结果进行验证,验证结果表明数值模拟与测量结果具有良好的一致性。认为利用有限元方法在进行核磁共振测井仪探头磁场的数值模拟可提高计算速度和精度。

Distribution of static magnetic field and RF magnetic field for the NMR logging tool affects resonance frequency, measured zone, depth of investigation, magnetic field gradient and signal intensity. Deduced is the magnetic field mathematical physics model of Nuclear Magnetic Resonance （NMR） logging tool by calculation. Established is the NMR logging tool sonde structure model, and simulated is the distribution of static magnetic field and FR field for centralized MRIL -P logging tool used Finite Element Method （FEM）. It is believed that the static magnetic field is gradient magnetic field in the sounding field. Static magnetic field numerical simulation results are verified by 3D magnetic scan and have good consistency with the measured results. It is coneluded that this method can improve calculation speed and accuracy of NMR logging tool sonde magnetic field numerical simulation