A Comparison of Different-Mode Fields Generated from Grounded-Wire Source Based on the 1D Model

Abstract

Abstracts-Traditional TEM study mainly focuses on the generation and application of the TE field using a loop or grounded-wire source; but in recent decades, lots of efforts have been made for implementation of the TM field and even the integration of the TE field with the TM one into anomaly detection in the subsurface. However, no applicable principles have been proposed for selecting the optimal electromagnetic field for various subsurface targets. The transient electromagnetic (TEM) fields generated from grounded-wire source consist of the TE-mode response (current-carrying wire), the TE-TM mode response (grounding ends) and the combined TEM-mode response (currentcarrying wire and grounding ends). This study performs a comparison of TE/TE-TM/TEM fields by generating them from grounded-wire source and testing their distribution characteristics, detection depth, and sensitivity to anomalies, using both synthetic 1D model and two field surveys in China. The comparisons demonstrate that, the detection depth of the TE-TM field is smaller than those of both the TE and combined TEM fields. Meanwhile, for electric field, the TE-TM response provides a better detection than the TEM one, but with an uneven distribution. Therefore, the TE-TM electric field requires well-designed arrangements of receiving positions when applied to real projects. For the magnetic field, the TEM response has the best detection capability compared to the TE and TE-TM ones, but is least sensitive to layer thickness and resistivity, especially for an embedded layer with low resistivity.

PFMD: A Power Frequency Magnetic Anomaly Signal Detection Scheme Based on Synchrosqueezed Wavelet Transform

“…The current mainstream electromagnetic instruments, such as V8 and GDP32, are all available for SOTEM measurement, providing favorable conditions to popularize this method. The SOTEM method has developed rapidly, with a relatively mature system of methods having been formed in the forward modeling, apparent resistivity calculation, inversion interpretation, and construction technology [40,41], and is widely and successfully applied in the areas of metal ore and coal hydrogeology [42][43][44][45].…”

Long-Distance Crosswell EM Logging of Copper Ore Using Borehole-Surface Current Injection in Slim Holes

“…In contrast to devices using a magnetic source, devices using an electrical source can use high power to expand the radiation range and are thus more suitable for deep exploration [24]- [26]. In addition, some researchers have investigated the fields generated by electrical and magnetic sources, and demonstrated that an electrical source can excite EM fields in both TE and TM polarization modes in the subsurface (where TE mode and TM mode are dependent upon the transverse electric waves and the transverse magnetic waves, respectively) [27]- [28]. Considering the complexity of the downhole environment and the safety of operation, crosswell EM detection methods based on electrical sources generally employ small-size electric dipole sources instead of long-wire sources [29].…”

Exploration of lead‐zinc deposits using electromagnetic method: A case study in Fengtai ore deposits in Western China

“…The detection depth of this method can reach approximately 2,000 m. Compared with traditional LOTEM methods, the short-offset grounded-wire TEM (SOTEM) method can produce a higher signal-to-noise ratio and achieve higher detection precision at shallow depth (<2,000 m). In recent years, many research achievements have been realized with this method, and excellent deep exploration results have been obtained in the fields of mineral deposits and hydrogeological prospecting (Chen, Xue, & Khan, 2016;Xue et al, 2013Xue et al, , 2020Xue, Chen, & Cheng, 2019;Zhou, Xue, Hou, Li, & Chen, 2017;Zhou, Xue, Hou, & Lu, 2018;Zhou, Xue, & Li, 2016).…”