油基钻井液多频随钻方位侧向电阻率成像测井响应研究

Logging Response of Multi-Frequency Azimuthal Laterolog Resistivity Imaging while Drilling in Oil-Based Drilling Fluid

  • 摘要: 针对油基钻井液环境下随钻电阻率成像仪器探测深度不足、方位识别能力有限的问题,提出了一种极板式接收结构的多频随钻方位侧向电阻率成像测井仪器。结合仪器工作原理,建立了等效电路模型与三维有限元模型,对均匀地层进行了模型验证,并进一步构建了四方位地层、高低阻异常体地层及倾斜层状地层,分析了不同频率下阻抗实部、虚部的响应规律及地层电阻率敏感范围。研究表明,等效电路响应结果与均匀地层有限元正演结果吻合较好;在四方位地层中,低频段实部和虚部对高、低阻层变化响应更明显,高频可辅助区分不同电阻层;异常体探测结果表明,方位张开角增大时响应幅度增强,且实部与虚部具有互补性;倾斜层状地层中,多频联合分析可增强层界面识别能力,并提高倾角计算的稳定性。多频方位侧向电阻率成像测井能够较好地表征复杂地层的方位电性差异,为油基钻井液条件下的成像测井研究提供了模型基础与方法参考。

     

    Abstract: To address the problems of insufficient detection depth and limited azimuthal identification capability of instruments for resistivity imaging while drilling in oil-based drilling fluid environments, a multi-frequency azimuthal laterolog resistivity imaging logging structure with plate-type receivers is proposed. Based on the instrument’s operating principle, an equivalent circuit model and a three-dimensional finite element model are established. Model validation is conducted in homogeneous formations. Furthermore, a formation with four azimuthal resistivities, a formation containing high- and low-resistivity anomalies, and an inclined layered formation were constructed to analyze the response characteristics of the real and imaginary parts of impedance at different frequencies and the sensitive range of formation resistivity. The equivalent circuit results show good agreement with the finite element forward modeling results in homogeneous formations. In the four-azimuth formation, the real and imaginary parts at low frequencies exhibited more pronounced responses to variations in high- and low-resistivity layers, while high frequencies can assist in distinguishing different resistive layers. The anomaly model indicates that the response amplitude increases with the enlargement of the azimuthal opening angle, and the real and imaginary parts exhibited complementarity. In the inclined layered formation, multi-frequency joint analysis enhances layer interface identification capability and improve the stability of dip angle calculation. The proposed multi-frequency azimuthal laterolog resistivity imaging scheme effectively characterize azimuthal electrical differences in complex formations, providing a model foundation and methodological reference for imaging logging research under oil-based drilling fluid conditions.

     

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