大深度激电法中电磁耦合效应分析与去除方法

    Analysis and removal of electromagnetic coupling effects in the large-depth induced polarization method

    • 摘要: 随着浅层矿产资源的逐渐枯竭,深部矿产勘探成为矿业发展的必然趋势,增大勘探深度最直接、最有效的方法是增加激电装置的供电极距。然而,长供电极距会引发强烈的电磁耦合效应,从而对激电信号造成严重干扰。针对这一问题,本文基于解析方法计算了不同测量装置在均匀半空间和层状介质中的电磁耦合效应,通过对比,分析了测量装置类型、布线方式、供电极距、大地电阻率及频率等因素对电磁耦合强度的影响。最后,根据激电效应和电磁耦合效应在频率域内相位的差异,推导了相对相位谱的计算公式,并针对不同的应用场景对其去耦效果进行理论分析。研究结果表明,供电极距的增大、大地电阻率的降低以及工作频率的升高均会显著增强电磁耦合的干扰强度。在相同条件及探测深度下,四极装置受到的电磁耦合干扰通常高于三极装置。相较于传统的激电相位谱,相对相位谱的引入使三极装置和四极装置的最大工作频率分别提高了4倍和10.6倍,表明相对相位法在大深度激电法勘探中具有一定的去耦效果。本研究对大深度激电勘探的现场施工具有重要的指导意义。

       

      Abstract: With the gradual depletion of shallow mineral resources, deep mineral exploration has emerged as an essential development trend in the mining industry. Increasing the distance between receiver electrodes of induced polarization (IP) devices is the most direct and effective approach to enhance the exploration depth. However, a long distance can cause strong electromagnetic (EM) coupling effects, severely interfering with IP signals. Addressing this challenge, this study calculated the EM coupling effects of various measuring devices in homogeneous half-space and layered media using analytical methods. Furthermore, this study comparatively analyzed the impacts of various factors, including measuring device type, wiring layout, distance between receiver electrodes, earth resistivity, and frequency, on the EM coupling intensity. Based on the phase differences between IP and EM coupling effects in the frequency domain, this study derived the calculation equation of the relative phase spectrum, followed by a theoretical analysis of the decoupling effects in application scenarios. The results indicate that increasing distance between receiver electrodes, decreasing earth resistivity, and raising working frequency all significantly intensified the EM coupling interference. Under consistent conditions and detection depths, the Schlumberger array suffered from higher EM coupling interference compared to the pole-dipole array. Compared to the traditional IP phase spectrum, the relative phase spectrum enhanced the maximal working frequency of the pole-dipole and Schlumberger arrays by four and 10.6 times, respectively, suggesting the decoupling capability of the relative phase method in large-depth IP exploration. Overall, this study provides significant guidance for the field implementation of large-depth IP exploration.

       

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