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核磁共振测井仪探头的优化设计能够增强仪器的探测特性,提高仪器的信噪比,而探头设计中的数值方法对设计结果至关重要.本文利用电磁场有限元方法对贴井壁型核磁共振测井仪探头静磁场和射频场进行了2D和3D的数值模拟,深入分析了数值模型形状、模型尺寸、单元形状对数值模拟结果的影响,并将有限元数值模拟结果与实测数据做了对比.结果显示:数值模拟结果与实测数据符合.在设计核磁共振测井仪探头结构时,选取与井眼形状一致的圆形模型,模型尺寸范围在10—15倍探头外径,并采用三角形单元可以有效提高数值模拟方法精度,增强优化设计结果的可靠性.
The optimized design of the NMR logging probe can enhance the detection characteristics of the instrument and improve the signal-to-noise ratio of the instrument, and the numerical method in the probe design is crucial to the design result.In this paper, the electromagnetic field finite element method The 2D and 3D numerical simulations of the static magnetic field and the RF field of the logging tool probe were carried out. The effects of the numerical model shape, the model size and the shape of the unit on the numerical simulation results were deeply analyzed. The results of the numerical simulation were compared with the measured data The results show that the numerical simulation results are in good agreement with the measured data.When designing the structure of the NMR logging instrument, a circular model with the same shape as the wellbore is selected. The model size range is 10-15 times the outer diameter of the probe, This method can effectively improve the accuracy of the numerical simulation method and enhance the reliability of the optimized design results.