Conventional surface electromagnetic methods have limitations of a shallow detection depth and low resolution. To increase the detection depth and resolution, borehole–surface electromagnetic methods for electromagnetic three-dimensional observations of the ground, tunnels, and boreholes have been developed. Current borehole receivers only measure a single parameter of the magnetic field component, which does not meet the special requirements of controlled-source electromagnetic (CSEM) methods. This study proposes a borehole electromagnetic receiver that realizes synchronous acquisition of the vertical electric field component in the borehole and the three-axis orthogonal magnetic field components. This receiver uses Ti electrodes and fluxgate magnetometers (fluxgates) as sensors to acquire electric and magnetic field components. Multi-component comprehensive observation methods that add the electric field component can effectively support the CSEM method, improve detection accuracy, and exhibit a strong potential for detecting deep ore bodies. We conducted laboratory and field experiments to verify the performance of our new borehole electromagnetic receiver. The receiver achieved a magnetic field noise of less than 6 $\mathrm{pT}{\mathrm{Hz}}^{-\mathrm{1}/\mathrm{2}}$ at 1 kHz, and the electric field noise floor was approximately 20 $\mathrm{nV}{\mathrm{m}}^{-\mathrm{1}}{\mathrm{Hz}}^{-\mathrm{1}/\mathrm{2}}$ at 1 kHz. The −3 dB electric field bandwidth can reach DC −10 kHz. The results of our experiments prove that high-quality CSEM signals can be obtained using this new borehole electromagnetic receiver and that the electric field component exhibits sufficient advantages for measuring the vertical component of the electric field.

中文翻译：

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为控制源电磁方法开发的新型钻孔电磁接收器

常规的表面电磁方法具有检测深度浅和分辨率低的局限性。为了增加检测深度和分辨率，已经开发了用于地面，隧道和钻孔的电磁三维观测的钻孔表面电磁方法。当前的井眼接收器仅测量磁场分量的单个参数，这不能满足受控源电磁（CSEM）方法的特殊要求。这项研究提出了一种钻孔电磁接收器，它可以实现对钻孔中垂直电场分量和三轴正交磁场分量的同步采集。该接收器使用钛电极和磁通门磁力计（fluxgates）作为传感器来获取电场和磁场分量。添加电场成分的多成分综合观测方法可以有效支持CSEM方法，提高检测精度，并具有很强的探测深矿体的潜力。我们进行了实验室和现场实验，以验证我们新型钻孔电磁接收器的性能。接收器的磁场噪声小于6 $\mathrm{T}{\mathrm{赫兹}}^{--\mathrm{1个}/\mathrm{2个}}$频率为1  kHz时，电场本底噪声约为20 $\mathrm{nV}{\mathrm{米}}^{--\mathrm{1个}}{\mathrm{赫兹}}^{--\mathrm{1个}/\mathrm{2个}}$在1  kHz下。该-3 dB的电场带宽可以达到DC -10千赫。我们的实验结果证明，使用这种新型钻孔电磁接收器可以获得高质量的CSEM信号，并且电场分量显示出足以测量电场垂直分量的优势。