Full field apparent resistivity definition of Borehole TEM with electric source

Wu, Junjie; Li, Xiu; Zhi, Qingquan; Deng, Xin; Jie, Guo

doi:10.2991/iceeg-16.2016.42

Cited by 3 publications

(4 citation statements)

References 7 publications

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“…This paper attempts to improve the ability to distinguish the anomaly and realize the fine detection of the deep structure. For this, the paper draws on the research results of the amplitude difference between the electromagnetic signals in the disturbance and the intact coal seam by Greenfield and Wu [20], and redefines the EA calculation method in equation (4). Then, it draws the EA multi-track curve with single anomaly and different lines, as shown in Figure 5.…”

Section: Ground-tunnel Observation Modementioning

confidence: 99%

“…Eaton and Hohmann [1], West and Ward [2] used the integral equation to study the anomalous G-W TEM field response characteristics under long wire sources; Yang et al [3] established a three-dimensional geological model and the overlay model, to analyse the response characteristics of the square low-resistance object and overburden layers as well as the influence factors of the overlayer. Wu et al [4] defined the global apparent resistivity of grounded source G-W TEM; in literature [5] they verified the effectiveness of G-W TEM for determining electrical interface under the condition of electrical emission source; their study in [6] further showed that the three-component transient response curve of G-W TEM has a good response to electrical interfaces and anomality. Xu et al [7] studied the vertical contact zone and its G-W TEM response characteristics when containing low resistance bodies; they also performed forward modelling of uniform half-space and vertical fault planes [8], and carried out three-dimensional forward modelling of G-W TEM, summarizing the main factors affecting G-W TEM anomalies [9]; Meng and Pan [10] calculated the G-W TEM anomaly response of low-resistance plate-shaped conductors in the case of homogeneous half-space and low-resistance coating, and studied the response characteristics and laws; Meng et al [11] believe that the response obtained by G-W TEM observation is the result of the interaction between the surrounding rock background field and the target anomaly field, and proposed that the earth medium will affect the observation results; Meng et al [12] calculated and analysed the multi-component response of the G-W TEM, obtaining the results that the response characteristics depend on the "diffusion, attenuation, distortion" process of the transient field in the formation under different conditions and the electromagnetic field state of the observed position.…”

Section: Introductionmentioning

confidence: 99%

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Numerical Simulation and Anomalies Qualification Based on Ground-well Transient Electromagnetics Method

Zhang¹,

Liu²,

Wu³

et al. 2019

EJEE

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The ground-well transient electromagnetics (G-W TEM) method is an important way to enhance the resolution and depth of detection, for its signals, emitted on the ground and received in the well or tunnel, are close to anomalies. This paper attempts to detect deep, small anomalies accurately through the G-W TEM. Drawing on the 2D finite-difference timedomain (FDTD) method and the ground TEM method, several field potential models were created for plate-shape conductors and square conductors at different depths and locations. The model construction was conducted with a large fixed loop as the emitter, assuming that the medium obeys uniform distribution. The signals were observed under the ground-borehole or ground-tunnel modes, and subjected to forward modelling, with the aim to disclose the response characteristics of small anomalies to the vertical magnetic field intensity (Hz) curve and multi-track electromagnetic absorption (EA) curves. On this basis, the author put forward an interpretation method that accurately locate small anomalies based on the extreme point of the Hz curve and the intersections of the EA curves. The research results show that the FDTD method can solve the established field potential models of linear conductors in an effective and accurate manner, and output the curve response characteristics of small anomalies; under the ground-borehole mode, the longitudinal position of each anomaly can be identified, and different anomalies can be distinguished based on the extreme point of the Hz curve, and the amplitude of the TEM response curve decreases with the elapse of time; under the groundtunnel mode, the lateral position of each anomaly can be identified, and different anomalies can be distinguished based on the intersections of EA curves, and the EA value is negatively correlated with the distance to the anomaly. To sum up, the proposed method pinpoints small anomalies based on the extreme point of the Hz curve and the intersections of the EA curves, and improves the resolution in both vertical and horizontal directions.

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Section: Ground-tunnel Observation Modementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Numerical Simulation and Anomalies Qualification Based on Ground-well Transient Electromagnetics Method

Zhang¹,

Liu²,

Wu³

et al. 2019

EJEE

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show abstract

“…The 1D inversion and apparent resistivity interpretation methods are suitable for understanding the electrical distribution of background strata, which is not conducive to displaying local targets [10][11][12][13][14]. The equivalent current filaments method can roughly delineate the scope and central position of the target body [15][16][17], but at present, there needs to be equivalence in the inversion of borehole data to some extent, which is not accurate enough to reflect the information of the target bodies [18,19].…”

Section: Introductionmentioning

confidence: 99%

Joint Inversion with Borehole and Semi-Airborne TEM Data Based on Equivalent Filament Approximation

Zhi

Deng

et al. 2022

Minerals

Self Cite

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The borehole transient electromagnetic (TEM) method can be useful in deep mineral exploration to detect blind ore bodies beside or below the borehole, and is especially adapted to finding small-scale, deep, rich ore bodies. In this method a transmitting loop is deployed on the top surface of the Earth, while a receiving coil is moved down the borehole. As the borehole TEM method is limited by the borehole’s location and depth, so its exploration scope is limited. The surface to airborne TEM method is a semi-airborne TEM configuration that transmits on the surface and receives TEM response in air. The two systems are combined into one system in this study, sharing the transmission loop deployed on the surface. With this combined system, the TEM response in the borehole and in the air can be observed at the same time. This paper employs a joint interpretation method based on the equivalent filament, which is introduced to obtain more reliable geometric information for the target with both borehole and aerial TEM data. The eddy currents induced in a thin confined conductor can be represented by equivalent current filaments, and the distribution of filaments can reflect the position and geometry of the conductor. Therefore, geometric parameters of targets can be obtained by filament inversion, and the joint inversion can be more accurate with both borehole and aerial response. Numerical modeling results show that the joint inversion based on the equivalent filament results can reliably obtain the geometric parameters of the thin conductive plate embedded in half space.

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“…Meng and Pan (2012) studied the surface-hole TEM responses of a conductive plate and analyzed the effect of conductive overburden [22]. Wu et al (2017) studied the approximate processing method of electric source borehole TEM and defined the full-field apparent resistivity [23]. Chen et al (2019) analyzed the full-component response of electric source surface-to-borehole TEM [24].…”

Section: Introductionmentioning

confidence: 99%

A Comparison of Surface-to-Coal Mine Roadway TEM and Surface TEM Responses to Water-Enriched Bodies

2019

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The surface transient electromagnetic method (TEM) is a geophysical technology normally used in detecting water-enriched zones. However, with an increase of mining depth, the accuracy and reliability of surface detection is gradually reduced, and surface TEM cannot meet the requirements of highprecision detection for coal mine production safety. In this study, surface-to-coal mine roadway TEM is proposed to detect water-enriched zones in coal mines. The resolution of this method in detecting targets, however, is still unknown. Based on a 1-D layered model, the surface-to-coal mine roadway TEM response is numerically simulated using the finite-difference time-domain method (FDTD). The results show that the surface-to-coal mine roadway TEM has higher resolution of the target above the underground receiving point and weaker resolution of the target below the receiving point. 3-D geo-electric models for typical waterenriched zones such as a water-filled mining goaf, a water-filled fault and a water-filled collapse column are established. The surface-to-coal mine roadway TEM responses are numerically simulated and compared with the surface TEM responses. The results show that for the goaf model, the surface-to-coal mine roadway TEM response is more sensitive than the surface TEM response. For fault and collapse column models, the surface-to-coal mine roadway response is more sensitive than surface response in the early delay stage but less sensitive in the late delay stage. The present study provides theoretical support for device selection and for data processing interpretation in actual work.INDEX TERMS Transient electromagnetic method, borehole, surface-to-coal mine roadway, water-enriched zones, numerical modeling.

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Full field apparent resistivity definition of Borehole TEM with electric source

Cited by 3 publications

References 7 publications

Numerical Simulation and Anomalies Qualification Based on Ground-well Transient Electromagnetics Method

Numerical Simulation and Anomalies Qualification Based on Ground-well Transient Electromagnetics Method

Joint Inversion with Borehole and Semi-Airborne TEM Data Based on Equivalent Filament Approximation

A Comparison of Surface-to-Coal Mine Roadway TEM and Surface TEM Responses to Water-Enriched Bodies

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