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This paper develops a novel method of 3D inversion of induced polarization (IP) survey data, based on a generalized effective-medium model of the IP effect (GEMTIP). The electrical parameters of the effective-conductivity model are determined by the intrinsic petrophysical and geometrical characteristics of composite media, such as the mineralizati...
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... In addition, an ellipsoidal grain filling-based GEMTIP model is proposed. For more information on the deri v ation of the GEMTIP model, please refer to related papers (Zhdanov 2008 ;Lin 2017 ;Zhdanov et al. 2018 ). Eq. ( 4 ) describes the filling process of multicomponent spherical grain media, and the filling of different grains is shown in Fig. 1 . ...
... Compared to the Cole-Cole model, the physical mechanism explained by the GEMTIP model is more intuitive. Therefore, some scholars have tried to apply the GEMTIP model to analyse IP phenomena in mineralized rocks and hydrocarbon-bearing reservoirs (Phillips 2010 ;Zhdanov et al. 2012 ;Lin 2017 ;Zhdanov et al. 2018 ). Other scholars have also attempted to build the modified IP models. ...
The induced polarization (IP) phenomenon describes the variation of resistivity with frequency and this geophysical method has been widely used to classify rock properties. Various experimental models have been developed to describe the mechanism of IP effect. The model based on the generalized effective-medium theory of induced polarization (GEMTIP) is an extension of the classic Cole-Cole model by considering electromagnetic inductions. Compared to the Cole-Cole model, the GEMTIP model can effectively incorporate rock composition and morphology to provide a more precise complex resistivity response. However, adding one more grain type to the GEMTIP model will result in adding three more parameters to the inversion process. Even for the GEMTIP model with only three-phase spherical grains, seven parameters need to be inverted. In general, the inversion of GEMTIP model with more than three phases is characterized by high uncertainty. Traditional geophysical inversion methods such as global optimization and least-squares optimization have certain limitations in inverting IP parameters. The effectiveness of least-squares optimization algorithm depends on the setting of initial inversion parameters. Efficiently processing massive amounts of data is challenging for both least squares optimization and global optimization algorithms. Considering the powerful search and generalization capabilities of neural network (NN), we develop a machine learning (ML) approach for efficient inversion of IP parameters based on long short-term memory (LSTM) networks with physical constraints. Compared with traditional methods, ML method can significantly reduce the computational cost and produce reliable inversion results. To validate the effectiveness of ML approach, we first conduct multiple synthetic model studies based on the Cole-Cole model and the GEMTIP model, respectively. We then further demonstrate the effectiveness of neural networks in recovering IP parameters from rock samples using measured data from man-made and field rock samples. The results show that the developed method can effectively obtain accurate inversion results based on Cole-Cole model and GEMTIP model.
... The physical and mathematical expression better reflects the shape, size, percentage content, resistivity, relaxation time, attenuation coefficient, and other structural and physical parameters of mineral particles in the study of the complex resistivity (CR) of rocks and ores. Given the GEMTIP model, many scholars around the world have conducted ore sample testing and multiphase medium CR simulation calculations (Phillips, 2010;Burtman and Zhdanov, 2015;Liu et al., 2015;Revil et al., 2015;Zhang et al., 2019), model parameter characteristic studies (Zhdanov et al., 2013;Wu et al., 2017;Chang et al., 2018), parameter fitting and inversion studies (Fu, 2013;Zhdanov M. et al., 2018;Sharifi et al., 2019), and practical application studies (Zhang et al., 2016;Zhdanov M. S. et al., 2018;Alfouzan et al., 2020) with meaningful results. Therefore, the anomaly characteristics of the CR spectra of two-phase, three-phase, and multiphase media in rocks and ores, as well as anisotropic distribution characteristics, can be studied based on the GEMTIP model. ...
To study the electrical characteristics of rocks and ores, two- and three-phase medium models with different mineral contents, attenuation coefficients, relaxation times, and ellipticities were established based on the generalized effective medium theory of induced polarization (GEMTIP) model and the Debye decomposition method. Furthermore, the corresponding program was written for numerical simulation, and the complex resistivity (CR) spectral characteristics and relaxation time distribution (RTD) characteristics were analyzed. At the same time, seven representative ore samples from different mining areas were selected, their structural compositions were observed, and their complex resistivity was measured to obtain the variation characteristics and Nyquist curves of ore phase spectra. The differential evolution (DE) algorithm was employed to write a curve parameter fitting program based on which parameter fitting was performed for the theoretical model and the measured curves of ore samples. The physical and electrical parameters of the curves were obtained, and the variation characteristics of each parameter were analyzed. The generalized effective medium theory of induced polarization model could be adopted to further study the induced polarization (IP) anomaly from the structural and electrical properties of rocks and ores, which has important guiding significance for energy resource exploration, deep prospecting beyond 500 m, and environmental investigation by electrical (magnetic) methods.
... The second one is the induced polarization method, which is generally applied to mineral exploration, for instance, gold [18][19][20][21][22][23][24][25], copper [26,27], and galena [28,29]. However, only a few researchers utilized it for underground cave detection, all deployed dipole-dipole arrays [12][13][14]. ...
One of the geopark tourism areas in East Lampung Regency, "Gua Pandan," has run into rock subsidence on the surface. As part of the subsidence prevention, indirect electrical methods between resistivity and chargeability profiling were applied to identify the presence of a subsurface cave in the study area. Two measurement lines were carried out with Wenner Alpha and Wenner Schlumberger arrays. Because the depth target is shallow (approximately 10 m) and to obtain a better resolution, each line has a stretch length of 70 m and 2 m electrode spacing. A line was measured over a known underground cave to produce a desired outcome, and the other was in an area with no cavities. Based on the results from each profile of resistivity and chargeability, an air-filled target has a value of over 5,000 and under 6 ms, respectively. Then, integrated processing of both methods generated a metal factor (MF) profile to view the presence and estimated shape of the cave/ cavities. The result represents that an MF value under 1.5 ms/Ωm is a cavity, and solid rock is over 1.5 ms/Ωm. Also, the MF level from both configurations delineates a similar section. However, a modest difference occurs in estimating the cavity shape geometry, for Wenner Apha and for Wenner Schlumberger. Furthermore, this study can be an initial step in safety assessment in the area.
... At the present stage, much research has shown evidence of the IP effects that appear in what is called the negative response phenomenon within the TEM responses [7,8]. Recently, interest in recovering IP parameters from the TEM (TEM-IP) data has increased considerably, which has also lead to a breakthrough in some significant applications, such as the exploration of minerals, hydrocarbons, water resources, etc. [9][10][11][12][13][14]. Moreover, high-precision detection and interpretation has extended the application of the TEM-IP method to the monitoring of permafrost, groundwater pollution, and weathered geology [15][16][17]. ...
Induced polarization (IP) effects in transient electromagnetic (TEM) measurement play a significant role in the detection of minerals, such as sulfide ore, clay ore, etc. However, due to the complex impacts caused by the polarization parameters, the structure of the earth, and the measurement system configuration, the IP effects cannot be easily measured and interpreted. We paid more attention to the vertical component of the ungrounded-TEM system in previous work; however, we will now attempt to utilize the horizontal component to enhance the precision of the measurement and interpretation. We quantitatively discussed the behavior of the horizontal and vertical magnetic fields of the towed-TEM (tTEM) system. We simultaneously introduced the vertical and horizontal components into the Jacobian matrix of the 1D laterally constrained inversion to build the joint inversion. Compared to the vertical component, the horizontal component always shows earlier and bigger sign reversals and contains more IP information. Inversion with the single horizontal or single vertical component showed poor accuracy in the deep and shallow layers, respectively. The joint inversion with both components could correct the errors. Including the horizontal component in the detection and interpretation facilitates an improved resolution for polarizable minerals.
... Recently, some authors proposed CSEMIP inversion combining EM induction and IP for a constant CR in 2. 5-D (MacLennan et al. 2014) and in 3-D (Commer et al. 2011). To our knowledge, only one research group worked to solve together EM induction and IP effects in 3-D considering a frequency-dependent resistivity based on an integral equation approach and the less common GEMTIP model (Zhdanov 2008;Zhengwei Xu & Zhdanov 2015;Zhdanov et al. 2018). Combining IP and CSEM methods are of increasing interest these late years to complete our knowledge of the medium in an increased range of frequencies. ...
... homogeneous half-space are investigated. Cubes dimensions and depth are close to the anomaly investigated by Zhdanov et al. (2018) without the extension in one horizontal direction. The first cube (cube 1) is a polarizable conductive cube with CC parameters ρ 0 = 10 .m, ...
In some Earth materials, significant induced polarization (IP) phenomena are occurring when an electric perturbation is applied. These mechanisms are described by a frequency-dependent complex resistivity (CR). The study of the CR spectral signature allows to access indirectly to several properties of interest of the subsurface linked to the interaction between the pore space and fluids. CR is usually studied using the electrical method with a direct current approximation, neglecting by the way electromagnetic (EM) induction that can occur in the data. However, EM induction increases with frequency and offset, resulting in limitations at high frequencies or for the investigation of deep target. We implemented a frequency-dependent CR in a 3D finite-differences (FD) modelling and inversion code for frequency domain controlled-source electromagnetic (CSEM) data to take into consideration IP information contained in EM data or reciprocally. The CSEM methods are resistivity imaging techniques using multi-frequency EM fields that fully take into account EM induction with large investigation depth. Following a preliminary sensitivity study, a multi-stage inversion framework was designed to constrain the multi-parameter inverse problem. Furthermore, to manage the increasing number of parameters, a second-order polynomial parameterization is used to describe independently frequency variation of CR norm and phase. We demonstrate the method through 1D and 3D synthetic data inversions for a deep-target model. We show that we were able to recover the CR and its frequency variation from CSEM data in the IP/EM coupling domain for 1D targets. The problem of deep polarizable 3D targets is more challenging and the resolution of the recovered CR spectrum was impacted. Nevertheless, we retrieved from a model containing several polarizable anomalies some crucial information allowing the discrimination of the targets from the non-polarizable background and from different spectral CR signatures. Our inversion strategy allows thus accessing to IP parameters of the medium in an extended frequency domain by fully taking EM induction information into account.
... The resistivity distribution of the stratum can be obtained by methods including TEM response analysis [9,10], apparent resistivity definition [11][12][13], and inversions [14][15][16][17][18]. However, due to the widespread polarizable medium [19,20] (typically, graphite and sulfide), the earth has inherent dispersion properties [21][22][23][24][25]. With the electromagnetic field propagating, the induced polarization (IP) response will occur in the stratum and superimpose on the TEM response. ...
The induced polarization (IP) effects in transient electromagnetic (TEM) responses pose difficulties to the TEM data interpretation and inversion. The IP effects break the monotony in TEM decay curves and can even cause sign reversals and lead to the singularity and non-monotony of inversion. The singularity problem is still urgent to be solved. In this paper, the forward modeling method of IP-affected TEM responses is developed using the Cole–Cole model and a frequency-time domain transformation. A TEM data acquisition scheme using a dual-source method without a significant increase in field work is proposed to weaken the singularity and improve the inversion quality finally. Based on the modeling and analysis, the dual-source scheme is designed to guarantee all stations be measured twice with different loops. The joint inversion of dual-source datasets is realized by using an objective combing function and the particle swarm optimization (PSO) algorithm. The synthetic data test proved the validity of the algorithm and illustrated that the joint dual-source method greatly weakened the singularity and stabilized the inversion. The field example of the Baiyun golden deposit showed well consistency with resistivity logging and TEM logging results and predicted the gold mineralization below 2000 m.
... Electrical resistivity and IP imaging allow the spatial distribution of the low-frequency resistive and capacitive characteristics of subsurface earth materials such as mineral ores, weathered or fresh rock, unconsolidated sediments, and, respectively, uncontaminated and contaminated soils [7][8][9][10][11][12][13]. These methods are extensively utilized in mineral exploration campaigns, engineering and environmental investigations, hydrogeological studies, and archeological prospecting [7,[14][15][16][17][18][19][20][21][22]. Both methods have proven successful in the mineral exploration arena worldwide because of their cost-effective and rapid ability to image natural shallow subsurface geologic structures with mineralization potential [7,8], with a certain degree of resolution dependent on the electrode spacing [23]. ...
This paper presents an underground silver mining operation outside Gomez Palacio, Du-rango, Mexico, which terminated around the 1930s, of which previous knowledge of its operations was poor. Durango's current silver exploration campaigns are likely to overlook historic silver mining sites due to interest in specific prospect regions. A two-dimensional (2D) Electrical Resistivity Imaging (ERI) survey coupled with reconnaissance of the area was performed at this historic silver mining site. The exploration campaign aimed to find the abandoned mineshaft, map its subsurface extent, and explore the occurrence of mineralization zones (silver ore). The ERI survey comprised five profiles measured with the extended dipole-dipole array with a consistent electrode spacing of 5 m. The smooth, robust, and damped least-squares inversion methods were used to invert the 2D data. Our field observations and ERI survey results collectively reveal the following findings: (a) reconnaissance reveals mining infrastructure consistent with historical mining activity; the infrastructure includes a complex of habitational rooms, an ore-processing pit near a concrete slab next to a dirt road, and two limestone-wall structures interpreted as the entrance of abandoned backfilled mineshafts named Mesquite and Lechuguilla; (b) high-resistivity anomalies suggest vestiges of shallow, underground mine workings including backfilled mineshafts that connect a mine gallery complex, and (c) various low-resistivity anomalies, juxtaposed against mine galleries, suggestive of unmined shallow vein-type and manto-type mineralization of hydrothermal origin. The imaging depth is estimated at ~65 m. Underground silver mining moved southwards and was limited to ~40 m depth.
... Using the same approximation, Commer et al. (2011) worked to implement a constant CR into their code detailed in earlier work . Only a group of authors to our known have developed a 3D inversion code inverting together EM induction and IP eect information considering a frequency-dependent CR using a CR model based on the GEMTIP model (Zhdanov, 2008;Zhdanov et al., 2018;Zhengwei Xu and Zhdanov, 2015). ...
... Two cubes of 200 meters with dierent CC properties embedded in a 100 Ω.m homogeneous half-space are investigated. Cube dimensions and depths are close to the anomaly investigated by Zhdanov et al. (2018). ...
In some Earth materials, induced polarization (IP) phenomena are occurring when an electric perturbation is applied. They are described by a medium with a frequency dependent complex resistivity (CR). In this work, a frequency dependent CR is implemented in a 3D finite-difference modeling and inversion code for controlled-source electromagnetic data (CSEM). The purpose of this work is to recover simultaneously IP and EM information. To constrain efficiently the multiparameter problem, the inversion is tackled through a multi-stage procedure, based on the electrical field sensitivity to CR. A versatile parametrization of the CR is proposed using second order polynomials. Using the multi-stage workflow on synthetic data and the polynomial parameterization, it was demonstrated that the CR could be correctly retrieved for deep 3D targets as well as their spectral behavior. This work helps extending the application domain of IP methods by taking EM information into account for the imaging.
... Two papers have been written on this inversion method which includes both full IC and determination of all four Cole-Cole parameters: [15,31]. This work was extended by [32] to apply full 3D inversion including EM effects and complex transmitter wire paths, and then to solve for four parameters of the GEMTIP model. ...
... The electric field at the receiver's midpoint is commonly used as the predicted data for modeling and inversion (e.g., [32]). This is typically a good approximation for dipole data, which only may differ from the actual data for the very near offsets (when distance between the transmitter and receiver dipoles is less than two times their length). ...
... The inversion is based on minimization of the Tikhonov parametric functional, ( ), with the corresponding stabilizer ( ) [32]: ...
The Saudi Arabian Glass Earth Pilot Project is a geophysical exploration program to explore the upper crust of the Kingdom for minerals, groundwater, and geothermal resources as well as strictly academic investigations. The project began with over 8000 km2 of green-field area. Airborne geophysics including electromagnetic (EM), magnetics, and gravity were used to develop several high priority targets for ground follow-up. Based on the results of airborne survey, a spectral induced polarization (SIP) survey was completed over one of the prospective targets. The field data were collected with a distributed array system, which has the potential for strong inductive coupling. This was examined in a synthetic study, and it was determined that with the geometries and conductivities in the field survey, the inductive coupling effect may be visible in the data. In this study, we also confirmed that time domain is vastly superior to frequency domain for avoiding inductive coupling, that measuring decays from 50 ms to 2 s allow discrimination of time constants from 1 ms to 5 s, and the relaxation parameter C is strongly coupled to intrinsic chargeability. We developed a method to fully include all 3D EM effects in the inversion of induced polarization (IP) data. The field SIP data were inverted using the generalized effective-medium theory of induced polarization (GEMTIP) in conjunction with an integral equation-based modeling and inversion methods. These methods can replicate all inductive coupling and EM effects, which removes one significant barrier to inversion of large bandwidth spectral IP data. The results of this inversion were interpreted and compared with results of drill hole set up in the survey area. The drill hole intersected significant mineralization which is currently being further investigated. The project can be considered a technical success, validating the methods and effective-medium inversion technique used for the project.
... Induced polarization (IP ;Bleil 1953;Wait 1959;Zonge & Wynn 1975;He1997) is an effective electrical resistivity tomography (ERT) method for non-ferrous metallic mineral exploration (Xi et al. 2013;Mary et al. 2016;Tavakoli et al. 2016) and environmental investigations (Revil et al. 2015;Maurya et al. 2018;Power et al. 2018). Currently, there has been great development of IP in forward modelling (Karaoulis et al. 2013;Commer et al. 2017;Belliveau & Haber 2018;Qi et al. 2019), data acquisition (Eaton et al. 2010;Sun et al. 2012;Olsson et al. 2015;Mo et al. 2017), inversion and interpretation (Li & Oldenburg 2000;Fiandaca et al. 2018;Kim et al. 2018;Soueid et al. 2018;Zhdanov et al. 2018). However, electromagnetic (EM) interference is still a major limitation that restricts the further application of IP method, for instance, EM coupling, civilization interference, low-frequency trend interference and so on (Peter-Borie et al. 2011;Larsen et al. 2013;Li et al. 2017). ...
Trend drift is an annoying background interference in induced polarization (IP) exploration, which has great influence on the final calculation of apparent complex resistivity spectrum at low frequency (< 0.1 Hz). This paper proposed a modified empirical mode decomposition (EMD) detrending technique for multi-period induced polarization data. The method uses local extreme values of the rising edges and the falling edges to form multiple envelopes and then to fit and eliminate the trend term. Through Comparing with the traditional EMD methods using IP data with simulated trend drift, we find that, the modified method can be used to obtain a more accurate fitting trend, and the computational cost is only a fraction of that of the conventional one. Additionally, this detrending is little affected by other strong noise. We also used IP data with and without trend interferences to analysis this method respectively. The results show that, for data without trend drift, the signals remain almost unchanged; however, for data with strong trend drift, the data quality is greatly improved, and the calculation error is reduced. This technique is also applied to a large-scale multi-period full-waveform induced polarization (IP) data acquired in Zhegu Zn-Sb-Ag polymetallic deposit in southern Tibet, China. The apparent complex resistivity and phase of a survey line, a planar contour map and a pseudo-section with and without using the modified EMD were compared respectively. Overall, before EMD detrending, the apparent phase results are rough and full of outliers. After detrending, the profiles are smooth and reasonable, and the outliers disappear. Both the results demonstrated that our proposed method can be adopted to effectively suppress trend drift interference without additional deviation in distributed full-waveform induced polarization exploration.
