Induced Polarization Research Articles

Rapid and Simple Method for Measuring Petroleum Asphaltenes by the Centrifugation Technique.

Asphaltenes are heavy constituents of crude oil which affect the flow and viscosity of crude oil. They also stabilize water-in-oil emulsions which makes the separation process of water from oil during the primary treatment processes for crude oils more difficult and costly. Measuring asphaltenes has great importance, especially for crude oil production companies. Gravimetric and spectroscopic measurement methods are the basic techniques used by international references such as ASTM and IP. A new methodology has been introduced as a modification of ASTM D6560 gravimetric methodology by using the centrifugation technique in the separation of asphaltenes for different oil samples with the API gravity change from 17.4 (oil S1) to 39.8 (oil S5). The new methodology has the advantages of consuming little time, and multiple sample processing and can be done in the field and also in the lab. Moreover, it has good repeatability, reproducibility, and working range values compared to the reference gravimetric ASTM and IP methods. The repeatability of the new method was found to be 8.0% at its maximum value (S1, has a low asphaltene content), while the minimum value was found to be 3.75% (S10, has the highest asphaltene content). It was found that the maximum reproducibility value was 17.0% for the S1 sample and the minimum was 0.0% for S9 and S10 samples.

Integrated geophysical investigation for lead and zinc mineralization in Wase, middle Benue Trough, Nigeria

There is an increasing demand for solid industrial minerals worldwide, as countries seek to support their economic growth. Wase, situated in Plateau State, is notable for lead and zinc mineralisation due to tectonic and hydrothermal activities in the region. The study utilises geophysical surveys to map mineralised zones of lead-zinc occurrence. These include ground magnetic survey, very low frequency electromagnetic, electrical resistivity tomography, and induced polarisation (IP). The field data were acquired using a GEMSys Overhauser magnetometer with VLF option and ABEM LS 2 Terrameter. twenty-nine (29) magnetic profiles with 50m spacing and a total length of 24.0 km were obtained and fifteen (15) very low frequency electromagnetic (VLF-EM) profiles with 10 m spacing in the E-W direction. A total length of 12.5 km was acquired across target areas of the magnetic profiles. The multiple-gradient electrode array of the ERT/IP surveys was used for data acquisition, and RES2DINV software by Geotomo was used for the inversion of the acquired data. High chargeability values corresponding to low resistivity values characterised zones with suspected lead-zinc mineralisation. Following this preliminary finding, we advise that further trenching, pitting, or core drilling be carried out to ascertain ore grade, possible beneficiation, and estimate of the reserve.

3D time-domain induced polarization modelling considering anisotropy and topography

Induced polarization (IP) method is one of the most widely used techniques in mineral exploration, hydrogeology, and environmental monitoring, becoming indispensable especially for metallic ore exploration. Topography of the surface and anisotropy of the subsurface plays an important role in the IP data interpretation and modelling leading to wrong resistivity and chargeability models if they are not considered. We developed a 3D IP forward modelling considering arbitrary anisotropy and topography using the finite element method (FEM). The newly developed algorithm is compared with the numerical solutions and analytical results for classical two-layer anisotropic models successfully. By using unstructured mesh to consider complex topography, we implement 3D IP forward modelling for arbitrary anisotropic medium under the condition of uneven terrain and investigate the effect of anisotropy and topography on IP data interpretation. Topography has a decreased or reinforcing effect on time-domain induced polarization (TDIP) response. Vertical transverse isotropic (VTI) medium has a tiny effect and can accurately locate the anomaly in the subsurface while tilted transverse isotropic (TTI) medium has a very large effect and cannot be explored. Under the comprehensive influence of complex topography and anisotropy with an angle larger than 30 degrees, it is very difficult to interpret TDIP results. The 3D inversion of the synthetic data derived by the 3D anisotropic chargeability model indicates that topography weakens the TDIP response. However, VTI anisotropic anomaly can be detected accurately in the horizontal direction, the TTI anisotropic anomaly is difficult to be explored.

Application of Induced Polarization and Resistivity to the Determination of the Location of Minerals in Extrusive Rock Area, Southern Mountains of Java, Indonesia

Mountainous areas often have a lot of natural wealth. The existence of geological appearances in the form of outcrops which are products of intrusion and alteration, indicates that the Pacitan area is a mineralized zone. In this study, geophysical measurements were carried out using the Induced Polarization (IP) method in the area where mineralization was suspected. The polarization induction method is expected to prove the presence of a mineralized zone in the Pacitan area. From the research results, line 1, line 4, line 5, line 6 and line 7 are areas with high chargeability values. So it can be proven that the area with high resistivity and high chargeability is an area with mineralization. Judging from the geological conditions on the surface, there are also outcrops which show that there is an intrusion and the result of alteration. So it can be concluded that the area has a fairly high mineralization. In measuring the correlation between magnetic anomalies and IP, the results are very supportive of each other that the area is a mineralized area, if we look at the resistivity, and chargebility.

Geophysical exploration and geological appraisal of the Siah Diq porphyry Cu–Au prospect: A recent discovery in the Chagai volcano magmatic arc, SW Pakistan

AbstractDiscovery of the Siah Diq porphyry (Cu–Au) prospect in the foothill of Dam Koh volcano is a recent exploration success story of mineralization buried under a 46 m alluvium cover in an exploratory mature Chagai belt. Acquisition of geophysical data followed by drilling and logging was key in the discovery. Integrated magnetics and induced polarization (IP) surveys in an area of 7.5 km2, pointed out magnetic-low, IP-high, and resistivity-low anomalies corresponding to porphyry Cu–Au type sulfide mineralization. Three bore holes were drilled to test the geophysical anomalies. After careful observation and geoscientific logging of core, porphyry style Cu–Au mineralization was revealed. The porphyry prospect was further characterized based on host rock lithology, petrography, alteration mineralogy, ore vein characterization, and Cu/Au geochemical assays based on core samples. Rocks hosting the mineralization include andesite, granodiorite, coarse, as well as fine grained diorite and pink granite, all highly altered, mineralized and porphyritic. Propylitic alteration was dominant in all the three bore holes and developed earlier followed by phyllic, potassic, and argillic alterations. Sulfide mineralization is present as cross-cutting stockwork veins and disseminations. Average copper and gold assays of drill core are 0.17% Cu and 0.78 ppm Au, respectively. Economically insignificant values of molybdenum and silver have been noted in some samples.

Mineralization Based on CSAMT and SIP Sounding Data: A Case Study on the Hadamengou Gold Deposit in Inner Mongolia

The Hadamengou deposit is the largest gold deposit in Inner Mongolia. However, given that the sources of ore-forming alkaline magmatic hydrothermal solutions and ore-controlling structures are still controversial, the theories behind the genesis of the deposit have been controversial. In this study, four controlled-source audio magnetotellurics (CSAMT) and spectral induced polarization (SIP) profiles in the mining area were used to obtain the underground resistivity model and the pseudo section map of the apparent frequency dispersivity based on fine inversion. In the resistivity model, there are two high-resistivity blocks with resistivity greater than 3000 Ω m and three low-resistivity channels with resistivity less than 50 Ω m. Combined with the regional geological and drilling data, it is inferred that the high-resistance bodies, R4 and R5, may be alkaline magmatic intrusions related to multiple stages of magmatic hydrothermal activities, ranging from the Precambrian to Yanshanian periods. The highly conductive channels, C3, C5, and C4, may represent the Baotou-Hohhot fault, secondary faults, and ductile shear zone, respectively, which were formed in the Precambrian era and underwent multiple activations during the Hercynian to Yanshanian period. According to the spatial relationship, it is inferred that the ductile shear zone is an important ore-controlling and ore-hosting structure. However, the Baotou–Hohhot fault may be a pre-metallogenic fault rather than an ore-controlling fault. By comparing the resistivity model with the pseudo section of the apparent frequency dispersivity, it was found that all the known gold veins are located in the superimposed area of low resistivity and high-frequency dispersivity. It is speculated that the ductile shear zone outside the alkaline magmatic rock with the superimposed characteristics of low resistivity and high-frequency dispersivity is the favorable area for mineralization.

Complex Resistivity Anisotropy Response Characteristics of Wufeng-Longmaxi Formation Shale in Southern Sichuan

Electrical exploration has become an important means of shale gas reservoir exploration and evaluation, and is expected to play a key role in the later stages of reservoir fracturing and development. At present, the research on the electrical response characteristics of shale gas reservoirs and their relationship with reservoir parameters is extensive and in-depth, but there is little research on their complex resistivity anisotropy characteristics and influencing factors, which restricts petrophysical modeling and reservoir parameter prediction, and reduces the reliability of shale gas exploration and reservoir evaluation by electromagnetic methods. In this paper, shale samples from the Longmaxi Formation and the Wufeng Formation of shale gas wells in southern Sichuan were collected, the complex resistivity of 34 shales in bedding direction and vertical bedding direction were measured, and the induced polarization (IP) parameters of shales were extracted by inversion. The electrical anisotropy response characteristics under different temperature and pressure conditions were analyzed, and the influencing factors and laws of complex resistivity anisotropy of shales were revealed. Combined with the test results of shale porosity and permeability, the evaluation model of resistivity, polarizability and porosity and permeability parameters was established. The research results have formed a set of testing methods and analysis techniques for electrical anisotropy of shale reservoirs, which are mainly based on complex resistivity parameter testing. It is helpful to understand the electrical anisotropy characteristics of shale gas reservoirs in southern Sichuan; this will provide the theoretical and physical basis for shale gas reservoir evaluation and fracturing monitoring by electrical exploration.

A novel approach to determine rock mechanical parameters using non-invasive geophysical methods

Engineering design of the major infrastructures mainly relies on determination of rock mechanical parameters. However, such indexes are traditionally acquired from the borehole tests of the construction site. The drilling test is generally time-consuming and costly procedure. Further, such tests provide geology information only at some specific points, need more equipment, are hardly carried out in the high topographic sites, and often leave ambiguity in the subsurface interpretation. Alternatively, geophysical research of ERT (electrical resistivity tomography) is swift, user-friendly, inexpensive and non-destructive, and can provide a bridge between the limited drilling tests and a true geotechnical model of the subsurface. In the present research, we introduce a novel geophysical approach to estimate rock mass integrity index (Kv) via integration between the ERT-based electrical resistivity and the limited borehole-based Kv. The obtained Kv offers 2D and 3D evaluation of rock mass integrity along all ERT profiles for large coverage of the project site where even no borehole data exist. Furthermore, uncertainty in the evaluation of water-clay distinction was removed by the integration of IP (induced polarization) with ERT. Our research, compared to the conventional geotechnical investigations, removes uncertainties in the geotechnical model and offers more accuracy in rock mass quality classification for various types of rock units. This approach removes the extensive drilling tests and offers a comprehensive assessment of rock mass integrity to achieve the proper design of engineered infrastructures in the highly heterogeneous terrains.

Development of formalin killed vaccine candidate against streptococcosis caused by Enterococcus sp. in Nile tilapia

Multiple bacteria under Streptococcus, Enterococcus and Lactococcus genera are considered to be associated with Streptococcosis. This study was conducted to develop and evaluate the effectiveness of whole cell formalin killed vaccine prepared from E. faecalis, E. hirae and E. faecium against the streptococcosis in Nile tilapia. To develop the candidate vaccine, efficacy of whole cell killed E. faecalis (strains BFF1B1 & BFTS22), E. hirae (strain BFTS29) and E. faecium (strain BFTS31) were evaluated. The vaccine prepared by mixing 3 % formalin and left for 24 h to kill the bacterial cells. Physiological saline (0.85 %) was mixed to the harvested formalin free killed cells to make final suspension for vaccine. This vaccine was administered to the fingerling tilapia (average weight 30 ± 5 g) by interperitoneal injection (IP) and bath immersion (BI) methods. The vaccinated group was monitored for 28 days to assess the developed immunity and vaccine safety into the fish. Post vaccination in vivo challenge test were performed against the pathogens. The hematological parameters (RBC, WBC, platelets and hemoglobin) and specific IgM were found significantly higher (p < 0.001) in the vaccinated fish compared to those in the non-vaccinated fish. The mean mortality in IP and BI method ranged from 10.0 ± 0.00 % to 23.3 ± 5.77 % and 18.33 ± 5.30 % to 40.0 ± 0.10 %, respectively. The relative percentage survival (RPS) in IP and BI varied from 68.78 % to 88.57 % and 59.52 % to 69.05%, respectively. Mortality was significantly lower in the immunized fish compared to those in non-immunized fish. The RPS were not different (p > 0.05) between IP and BI vaccination method. Formalin killed vaccine showed an excellent efficacy against Enterococcus sp. infection in Nile tilapia by IP method although bath immersion could also be an alternative.

Imaging hydraulic conductivity in near-surface aquifers by complementing cross-borehole induced polarization with hydraulic experiments

Precise information about the spatial distribution of hydraulic conductivity (K) in an aquifer is essential for the reliable modeling of groundwater flow and transport processes. In this study, we present results of a new inversion procedure for induced polarization (IP) data that incorporates petrophysical relations between electrical and hydraulic parameters, and therefore allows for the direct computation of K. This novel approach was successfully implemented for the Bolstern aquifer analog by performing synthetic IP experiments with a combined surface and cross-borehole setup. From these data, the distribution of K was retrieved with high accuracy and resolution, showing a similar quality compared to images achieved by hydraulic tomography. To further improve the quantitative estimates of K, we use synthetic pumping test data to inform two novel calibration strategies for the IP inversion results. Both calibrations are especially helpful for correcting a possible bias of the IP inversion, e.g., due to resolution limitations and/or to bias in the underlying petrophysical relations. The simulation of tracer experiments on the retrieved tomograms highlights the accuracy of the inversion results, as well as the significant role of the proposed calibrations.

Delineation of kaolinised and aquifer formations using electrical resistivity tomography (ERT) and induced polarization (IP) techniques

Delineation of kaolinised and aquifer formations using electrical resistivity tomography (ERT) and induced polarization (IP) techniques

Penalties From 2D Grating Coupler Induced Polarization Crosstalk in Silicon Photonic Coherent Transceivers

Silicon photonic two-dimensional grating couplers for C- and O-band dual-polarization coherent transceivers are analyzed with respect to their polarization splitting/combining performance. Due to scattered light in the grating's plane, a linear cross-polarization results. The latter is responsible for a limited polarization split ratio and a polarizations' non-orthogonality. The impact of these two quantities is evaluated by system-level simulations with regard to OSNR penalties in coherent systems. For both C- and O-band, a design modification for reduced penalties is proposed.

A Set of In-Well Receiver Array for Borehole Induced Polarization Detecting Technology in Deep Mine Exploration

With the rapid development of the economy, the demand for mineral resources has increased dramatically. Because it is difficult to explore new mines in deep and peripheral areas, new theories, technologies, methods, and equipment are needed. How to accurately and effectively carry out new mine exploration has become an urgent research topic. In this study, based on the requirements of mine exploration within a depth of 3000 m, an array receiver for borehole-induced polarization was developed. Each channel of the receiver array independently acquires data, and it is able to carry out full waveform acquisition in the dual voltage and voltage difference mode. The structure of the receiver array can be flexibly adjusted to obtain array observations of induced polarization in different ways. Experiments demonstrated that the device works well at a high temperature of 155 °C, its resolution reached 0.1 μV, and the error between the different channels was less than 3%. Its dynamic range is 180 db. Through experiments on induced polarization in a demonstration mining area, the apparent resistivity curve and the apparent polarization curve were determined to be consistent with the known well-logging information, and the interpretation results were in agreement with the stratum information.

The Influence of Magnetic Minerals on Induced Polarization Measurements in Sedimentary Rocks

AbstractInduced polarization (IP) measurements in porous sedimentary rocks are modeled in terms of pore geometrical descriptors (PGD). Using an extensive data set composed of 241 sandstone, carbonate, and arenite samples, we identified a stronger relationship between IP parameters and volumetric magnetic susceptibility versus IP parameters and PGD. This finding suggests that even small concentrations of iron minerals in rocks typically thought to lack electron‐conducting minerals can significantly influence IP measurements. The combination of magnetic susceptibility with a pore geometrical descriptor term improves the empirical prediction of IP measurements relative to the use of pore geometrical descriptor terms alone. This suggests that small concentrations of iron minerals exert a strong control on the specific capacitance, a property that remains poorly understood. The lack of any relationship between magnetic susceptibility and the PGD confirms that the magnetic susceptibility provides additional information unrelated to PGD.

Numerical Simulation Study on the Relationships between Mineralized Structures and Induced Polarization Properties of Seafloor Polymetallic Sulfide Rocks

The induced polarization (IP) method plays an important role in the detection of seafloor polymetallic sulfide deposits. Numerical simulations based on the Poisson–Nernst–Planck equation and the Maxwell equation were performed. The effects of mineralized structures on the IP and electrical conductivity properties of seafloor sulfide-bearing rocks were investigated. The results show that total chargeability increases linearly as the volume content of disseminated metal sulfides increases when the volume content is below 20%. However, total chargeability increases nonlinearly with increasing volume content in vein and massive metal sulfides when the volume content is below 30%. The electrical resistivity of disseminated metal sulfides mainly depends on the conductivity of pore water. The electrical resistivity of vein and massive sulfides mainly depends on the volume content and the length of sulfides. Increase in the aspect ratio (0.36 to 0.93) of seafloor massive sulfides causes relaxation time constants and total chargeability to decrease. Relaxation time constants and total chargeability also decrease with increase in the tortuosity of seafloor vein sulfides from 1.0 to 1.38. This study is of great value for the electrical survey of seafloor polymetallic sulfide deposits.

A study of time spectrum identification of induced polarization field based on Weibull distribution function

Identification of time spectrum is one of the core issues of the time-domain induced polarization (IP) method, which can be considered as one of the bases for distinguishing various polarized rocks. Fitting the IP data based on the spectrum forward model and obtaining optimal solution of the model parameters is a key step in spectrum identification. However, the suitable forward model should consider the observation conditions, such as the charging time and the time window. The time spectrum identification may be difficult to implement stably due to the lack of objective reference for the optimal solution. Therefore, our purpose is to improve the forward model and implement the spectrum identification for IP data. First, using the Weibull (WB) distribution function as the basis, a time spectrum forward model considering the charging time and observation time window is provided according to the typical measurement mode. Then, based on the WB spectrum model and Barzilai-Borwein gradient optimization, a method for solution of apparent spectral model parameters for spectrum identification is developed. Finally, this method is used to process the IP data from a mine in which the anomalies related to ore-bearing beds are identified based on the processing results. Results obtained demonstrate that the spectrum forward model based on the WB function is feasible in describing the IP data. The limited charging time and a wide observed time window should be considered to realize accurate simulations and description of the time-domain IP data. The essence of the time spectrum identification is to comprehensively reflect the time-varying state of the whole time channel through the spectral model parameters, whereas the decay field ratio of the adjacent time channel can be used as an objective reference. The parameters of the spectrum model characterizing the time-varying state are independent of polarization and resistivity and thus can be directly used for identification of IP anomalies.

Application of induced polarization imaging across different scales to understand surface and groundwater flow at the Hofermuehle landslide

Understanding changes in hydraulic properties of the subsurface is critical to delineate areas susceptible for groundwater accumulation and the triggering of landslides. Laboratory studies have demonstrated the possibility to estimate the hydraulic conductivity from induced polarization (IP) measurements. However, to-date only rare studies have been applied at the field scale and none has evaluated the frequency-dependence in field IP imaging data. We show that the application of petrophysical models linking hydraulic conductivity (K) and IP at 1 Hz, resolves for the same estimations from frequency-domain measurements as well as from time-domain IP. Moreover, our IP images reveal an evident frequency-dependence between 0.1 and 240 Hz in the electrical properties, which is also observed in lab measurements conducted in soil samples. To account for this, we fit a Cole-Cole model to our multi-frequency IP results and evaluate models linking K and the normalized chargeability, gaining a subsurface model of the hydraulic conductivity with enhanced resolution. Our results reveal clear variations at depth in the electrical conductivity and polarization associated with the presence of a plane of instability and the sliding plane. We also resolve lateral changes delineating areas with K below 10-6 m/s, which may act as barriers for groundwater flow. To evaluate our results we also estimate the hydraulic conductivity using a joint inversion algorithm that directly solves for porosity and saturation through the simultaneous inversion of seismic refraction and electrical resistivity tomography data. We observed consistent hydraulic conductivity images obtained through the inversion of the IP data and the joint inversion, with such model being in agreement with existing information of the site. We resolve a 3D model of the hydraulic conductivity at the Hofermuehle landslide from IP data that reveals the geometry of areas with poor drainage that may lead to land sliding.

Hard-rock investigation using a non-invasive geophysical approach

Investigation of a hard-rock terrain is essential for the development of engineering infrastructures and groundwater assessment. In such investigations, evaluation of rock mass quality and faults/fractures is a challenging task. Conventionally, borehole tests are conducted to acquire subsurface geological information, and rock mass quality parameters such as rock quality designation (RQD). However, such tests are expensive, slow, limited to some specific locations, require more equipment, provide point measurements, and are hardly conducted in a steep topographic terrain. Generally, the non-invasive geophysical methods, such as geoelectrical methods are performed to assess the hard-rock sites. However, such parameters alone provide ambiguity in interpreting the geological units. In this work, a joint approach of four geophysical parameters (e.g., electrical resistivity (ER), self-potential (SP), magnetic, and induced polarization (IP)) is proposed to assess a highly heterogeneous terrain for the installation of the Accelerator Driven System (ADS) facility in South China. Geophysical data were obtained via a variety of surveyed parameters along different profiles. Electrical resistivity tomography (ERT) was integrated with borehole tests data to determine RQD for rock mass quality evaluation over the entire area. The results of magnetic interpretation were calibrated with well data to constrain the subsurface into distinct layers. ERT and magnetic coupled with Joint Profile Method (JPM) detected several localized faults/fractures. IP was integrated with ERT to distinguish between water and clay. Groundwater flow path was marked using SP. Compared with the past investigations, this novel approach deciphers functional analogous relation of RQD with ERT, magnetic, IP and SP in the hard-rock, provides thorough insights into the subsurface, removes the ambiguity caused by single geophysical parameter or the inadequate well data, and bridges the gaps between accurate geological model and the limited data for the development of engineering structures and groundwater resources.

Combining geophysical methods (DC, IP, TDEM and GPR) to characterise mining waste in the Linares-La Carolina district (southern Spain)

The accumulation of waste materials in old, abandoned mining districts without prior sealing of the substrate currently poses a significant risk of contamination to soils and surrounding waters. Some of these mining dams have undergone a reclamation and sealing process in recent years to alleviate this problem. The current study is an analysis of the effectiveness of using different geophysical techniques for characterising these structures and monitoring the isolation performed. This study was carried out in the old mining district of Linares-La Carolina (southern Spain). The following techniques were investigated in this study: direct current (DC) resistivity, induced polarization (IP), ground-penetrating radar (GPR) and the time domain electromagnetic method (TDEM).Combining DC and IP made it possible to characterise the internal structure of the abandoned mining dams, whereby the geometry of these deposits was determined and the corresponding potential risks were assessed. In addition, percolation zones of mining leachates were detected that indicate defects in the sealing stage.TDEM was a good complementary technique for calculating the depth of the bedrock on which the mining dam is located. GPR could only be used to investigate shallow depths at all of the antenna frequencies used (100, 250 and 500 MHz) but was useful for obtained detailed information about the last stages of filling and characterising the encapsulation performed during sealing.

Quantifying Reagent Spreading by Cross‐Borehole Electrical Tomography to Assess Performance of Groundwater Remediation

AbstractIn situ remediation of contaminated groundwater often relies on the installation of a treatment zone (TZ) degrading the contamination. Zero‐valent‐iron (ZVI) is a type of reagent used for this purpose. Adequate delivery of ZVI in the whole target volume is particularly challenging and requires monitoring with high spatial resolution. We present a monitoring tool for imaging the dynamic spreading of ZVI and its associated ionic cloud, using cross‐borehole time‐lapse electrical resistivity tomography (ERT). This tool works in urban areas and is particularly suitable for achieving the required spatial resolution at the scale of the target volume. Groundwater and sediment samples show a consistent spatial and temporal distribution of the remediation cloud with cross‐borehole ERT. Yet, the 2D anomalies observed with cross‐borehole ERT provide a more spatially complete and rapid image of the remediation cloud distribution than if based solely on monitoring screens. At the study site, ZVI injection leads to uneven spreading, clearly documented by cross‐borehole ERT monitoring. The benefit of hydraulic conductivity (K) mapping by cross‐borehole induced polarization (IP) to understand unexpected injection paths (upstream leakage, spreading in preferred pathways) is investigated. A 2D, IP‐based, continuous, and coherent K‐distribution is obtained that compares well with estimations by grain size analyses from the TZ. However, the IP‐based K‐field fails at predicting injection paths, suggesting the creation of pathways during the high‐pressure injection of ZVI. Cross‐borehole time‐lapse ERT is the most promising geophysical tool for performance assessment of in situ remediation involving reagents with conductivity contrast.