Electromagnetic coupling analysis and removal in large-depth induced polarization method by using the relative phase

As shallow mineral resources continue to deplete, deep mineral exploration has emerged as an essential trend in the mining industry. One of the most direct and effective methods to enhance exploration depth is by increasing the spacing of the current electrode in the array. However, this increase often results in a stronger electromagnetic (EM) coupling effect, which can significantly interfere with the induced polarization (IP) signal. To address these challenges, this paper calculates the EM coupling effects of various measuring arrays in both uniform half-space and layered media using analytical methods. Based on these calculations, we further analyze the impact of various factors on the intensity of EM-coupling interference in the layered media model, including the type of measuring array, the spacing of the current-electrodes, as well as the resistivity and frequency. Ultimately, based on the differences in the phases of the IP and the EM-coupling in the frequency domain, we derive the calculation formula of the relative phase method and analyze its decoupling effect at various application scenarios. The results indicate that an increase in the spacing of the current electrode, a decrease in ground resistivity and an increase in working frequency will significantly enhance the intensity of EM coupling interference. Under consistent conditions and detection depths, the EM coupling interference is typically greater for Schlumberger array compared to pole-dipole array. By employing the relative phase method, the biggest working frequency of the pole-dipole array can be enhanced by a factor of four, while the Schlumberger array can experience an increase of 10 to 11 times. It demonstrates that the relative phase method has a certain effect for removing the EM-coupling in large-depth IP exploration. The research provides significant guidance for the field implementation of large-depth IP exploration.