Self-potential Method Research Articles

Application of Self-Potential Method in Mapping Leachate Flow Around Rasau Jaya Landfills, Kubu Raya Regency

This study uses the self-potential method to map the leachate flow around the Rasau Jaya landfill, Sungai Raya District, Kubu Raya Regency. The study was carried out in 2 areas, the north and south of the landfill. Data acquisition using a fixed base configuration by applying ten lines. Each line has a length of 105 m with 5 m, and the distance between the porous pots is 5 m. The measurement results show that the potential value distribution at the first location is -19.62 mV to 8.44 mV, and the potential value at the second location is -55.50 mV to 23.26 mV. The interpretation shows that leachate accumulation from the landfill in the first area has a potential value of -19.62 mV to -13 mV. The second location has a potential value of -55.50 mV to -36 mV. Based on isopotential contour maps, leachate accumulation in the first location is thought to be in the north to northeast of the landfill, while in the second location, it is thought to be in the southwest to the west of the landfill.

Assessment of Unconfined Aquifer Hydraulic Characteristics Using Self-Potential Method: Case Study in Laylan Sub-Basin, Kirkuk, Iraq

This study aims to evaluate the hydraulic characteristics of the unconfined aquifer in the Laylan area, Kirkuk, Iraq. The pumping test was carried out on four wells in the Laylan area. all wells penetrate the quaternary sediment, which consists of sand, gravel and clay, the monitoring of the change in the groundwater table was carried out by the groundwater depth detector and the self-potential device, as the purpose of this study was to find an alternative to the traditional methods that monitor the draw down during pumping test, whose use is often accompanied by many obstacles and especially most of the wells belong privately to the farmers, where the goal was to find a relationship between the self-potential readings and the change of the water depth that measured by groundwater depth detector. a mathematical relationship was obtained that links the values of the two variables. In addition, the conductivity value was calculated by substituting the self-potential value in the equation to find the draw down values and then entering into the aquifer-win program. The geophysical self-potential value is very sensitive to the groundwater level changes the correlation coefficient between each of them as in the wells (pw1, pw2, pw3 ) is 0.95,-0.83 and -0.86 respectively, It is a strong and inverse relationship. Transmissivity values for the wells PW1,PW2,PW3 ,PW4 were 12.32 m2 /day, 17.22 m2/day, 78.29 m2/d (10 m2/d) respectively and the hydraulic conductivity for the wells PW1, PW2, PW3, PW4 were 0.113 m/day, 0.21 m/day, 1.74 m/day, 0.25 m/day respectively the obtained hydraulic conductivity value was an approach to the hydraulic conductivity values obtained in the traditional methods. Therefore, the equation can be used in aquifers if it was in the same conditions as this basin. Therefore, the SP device can be considered a successful alternative to traditional measurement methods.

Correlation of 2D Electrical Resistivity and Self-Potential Methods for the Assessment of the Integrity of Goronyo Dam NW Nigeria

Abstract In this research, combined 2D electrical resistivity and self-potential (SP) methods were employed to locate anomalous electrical conductivity around the Goronyo dam in order to determine the condition of the embankment of the earth dam. The data were taken with the reference to resistivity and SP values using Wenner configuration. The results obtained from these techniques shows that the area was underlain by four stratigraphic layers, namely; clayey sand, wet sandy clay, laterite and partially weathered basement complex rock as compared with the resistivities of common rocks and borehole lithology of the area. The low SP (< 200 mV)/high resistivity zones in the overburden of profiles P1, P2 and P3 shows the presence of partially weathered basement complex rocks which was probably due to compactness and dryness around the dam. However, the zones of high SP (≥ 200 mV)/low apparent resistivity regions (z1 and z2) of profiles P1 (2 Ωm to 27 Ωm), P2 (3 Ωm to 25 Ωm) and P3 (3 Ωm to 14 Ωm) have revealed the weak zones associated with wet sandy soil. Results obtained from 2D electrical resistivity (z1) technique have correlated well with the results of SP sections (z2). These regions of weak zones occupied the x-distance along the profiles; P1/or S2 (120 m to 200 m and 250 m to 400 m), P2/or S2 (1 m to 156 m and 192 m to 400 m) and P3/or S3 (48 m to 400 m) with their corresponding depth y, ranging from 23 m to 30 m, 26 m to 30 m and 23 m to 30 m. Keywords: 2D Electrical Resistivity Tomography (ERT), Self-Potential (SP), Dam, Subsurface, Seepage, Condition

Interpreting Self-Potential Signal during Reactive Transport: Application to Calcite Dissolution and Precipitation

Geochemistry and reactive transport play a critical role in many fields. In particular, calcite dissolution and precipitation are chemical processes occurring ubiquitously in the Earth’s subsurface. Therefore, understanding and quantifying them are necessary for various applications (e.g., water resources, reservoirs, geo-engineering). These fundamental geochemical processes can be monitored using the self-potential (SP) method, which is sensitive to pore space changes, water mineralization, and mineral–solution interactions. However, there is a lack of physics-based models linking geochemical processes to the SP response. Thus, in this study, we develop the first geochemical–geophysical fully coupled multi-species numerical workflow to predict the SP electrochemical response. This workflow is based on reactive transport simulation and the computation of a new expression for the electro-diffusive coupling for multiple ionic species. We apply this workflow to calcite dissolution and precipitation experiments, performed for this study and focused on SP monitoring alternating with sample electrical conductivity (EC) measurements. We carried out this experimental part on a column packed with calcite grains, equipped for multichannel SP and EC monitoring and subjected to alternating dissolution or precipitation conditions. From this combined experimental investigation and numerical analysis, the SP method shows clear responses related to ionic concentration gradients, well reproduced with electro-diffusive simulation, and no measurable electrokinetic coupling. This novel coupled approach allows us to determine and predict the location of the reactive zone. The workflow developed for this study opens new perspectives for SP applications to characterize biogeochemical processes in reactive porous media.

Characterization of the non-Gaussian hydraulic conductivity field via deep learning-based inversion of hydraulic-head and self-potential data

Accurate characterization of the spatial heterogeneity of hydraulic properties such as hydraulic conductivity (K) is essential for understanding groundwater flow and contaminant transport processes. Deep learning-based ensemble smoother methods have proven to be effective in estimating non-Gaussian K fields by assimilating hydrodynamic measurements. However, traditional hydrogeological investigations (e.g., hydraulic tomography) often suffer from the limited number of invasive borehole data (e.g., hydraulic head), making the non-Gaussian K inversion problem strongly underdetermined. As a non-invasive and high-sampling-density geophysical approach, the self-potential (SP) method can measure fluctuations of the electrical field caused by subsurface fluid movement. Thus, the recorded SP signals are electro-kinetic responses of the groundwater flow and can provide complementary information for delineating non-Gaussian heterogeneity. In this paper, we performed a joint hydrogeophysical inversion of hydraulic-head and SP data to characterize the non-Gaussian K field within a deep learning-based inversion framework. We conducted three synthetic cases in a 3-D non-Gaussian aquifer with 16,000 unknown K, to assess the ability of the proposed joint inversion framework for K imaging by assimilating different types of data. The results show that using limited hydraulic-head data alone may capture the large-scale features of the non-Gaussian reference field but might lose fine features. By integrating the hydraulic-head and SP data, the non-Gaussian K field can be reconstructed with an improved accuracy and reduced estimation uncertainty. The low-cost SP method opens up new opportunities for non-Gaussian K characterization and fluid-dynamic monitoring.

Natural disaster mitigation using geophysical methods

The research has been carried out about natural disasters (landslides, ground motion, drought) using geophysical methods. This research was conducted in several places, in East Java, i.e. land slides and ground motion occurred in Malang and Blitar areas and drought occurred in theTulungagung and Malang areas. This research uses resistivity and self-potential. The active method is resistivity, which means that an electric current is injected into the earth, after which the resulting potential difference is recorded, then processed. Self-potential and geomagnetic methods, are passive methods. In the self-potential method, the potential difference that occurs between two points, which have a certain distance, is recorded (the middle between those two points becomes a point measurement). The data of several points of measurement, that have been made within a certain distance, then is processed for determining underground river tracing. The equipment used is the OYO Mac Ohm resistivity meter. The results obtained are, an artesian well in the Tulungagung area, at a depth of 108 m, an indication of new faults in the Blitar area, and ground motion cracks in the Malang area.

Диагностика утечек загрязненных вод с территории полигона отходов химического производства методом естественного электрического поля

The main goal of the research is a diagnostic assessment of polluted water leaks from the chemical waste landfill site using the self-potential method integrated with other methods. The following tasks were to be solved: locating zones of contaminated water leakage from the drainage canals; detecting polluted water leaks from the sludge reservoir; identifying the discharge zones of contaminated groundwater into the swamps adjacent to the landfill. Electrical prospecting equipment ERA-MAX with non-polarizable electrodes of the VIRG system was used for field measurements. Two measuring techniques of the self-potential method were used: the fixed-base method (the measurement interval was 5 m) and the potential gradient method (measuring line MN = 5 m). The additional methods were as follows: geomagnetic microsurvey and phytoindication. The following diagnostic indicators were estab-lished for the zones of infiltration of contaminated waters from canals and sludge reservoirs: negative fixed-base potential anomalies or negative potential gradient anomalies of the natural electric field, which are characterized by the amplitude of 10-40 mV. The area of discharge of polluted groundwater into the surficial unit is indicated by a positive anomaly of the natural electric field (+ 20-47 mV), spatially associated with the zone of degradation of swamp vegetation

Application of Optimal Control to Inversion of Self-Potential Data: Theory and Synthetic Examples

Last decades, there has been an increased interest in the use of the self-potential (SP) method in hydrogeophysics. In response to this strong interest, we develop a novel approach to the inversion of SP data. Mathematically, the SP inverse problem is the source identification problem for the Poisson equation. Our approach substantially differs from the standard regularization approach, which explicitly includes the forward-problem operator into the cost functional. We formulated the inverse problem is as an optimal control problem and then translate it into a variational system. The system is approximated in suitable finite-element spaces giving rise to an algebraic problem with the saddle-point structure. In contrast to the standard approach, which leads to a dense linear system, our method results in a system with a sparse block matrix. It can be efficiently solved by either direct sparse solvers or preconditioned iterative solvers. In this paper, we present the formulation of the problem and its finite-element approximation. We discuss the iterative solution and preconditioning strategies. Our software implementation is based on an industrial finite-element package. We also present a numerical experiment with node-based linear finite elements on tetrahedral grids. Our results suggest that the proposed approach may serve as a rapid and reliable tool for large-scale SP inverse problems. Moreover, the same technique can easily be extended to a wide range of geophysical linear inverse problems, such as inversions of magnetic and gravity data.

Towards the development of an automated electrical self-potential sensor of melt and rainwater flow in snow

AbstractTo understand snow structure and snowmelt timing, information about flows of liquid water within the snowpack is essential. Models can make predictions using explicit representations of physical processes, or through parameterization, but it is difficult to verify simulations. In situ observations generally measure bulk quantities. Where internal snowpack measurements are made, they tend to be destructive and unsuitable for continuous monitoring. Here, we present a novel method for in situ monitoring of water flow in seasonal snow using the electrical self-potential (SP) geophysical method. A prototype geophysical array was installed at Col de Porte (France) in October 2018. Snow hydrological and meteorological observations were also collected. Results for two periods of hydrological interest during winter 2018–19 (a marked period of diurnal melting and refreezing, and a rain-on-snow event) show that the electrical SP method is sensitive to internal water flow. Water flow was detected by SP signals before it was measured in conventional snowmelt lysimeters at the base of the snowpack. This initial feasibility study shows the utility of the SP method as a non-destructive snow sensor. Future development should include combining SP measurements with a high-resolution snow physics model to improve prediction of melt timing.

Geological and tectonic preconditions for hydraulic heterogeneity of the rocks in the area of the Gotse Delchev valley

Hydrogeological conditions largely depend on the permeability of the geological environment. In areas with complex geological and tectonic conditions, the detection of hydraulic heterogeneity of the rocks and determination of groundwater-rich zones is a challenge for hydrogeological practice. The aim of the study is to analyze the geological and tectonic prerequisites for hydraulic heterogeneity of the sediments for the Gotse Delchev valley (Southwestern Bulgaria), which predetermine the degree of their water productivity. In order to obtain more precise data for specific sites, a geophysical survey was conducted. The Self-Potential method was chosen, which is one of the most commonly used techniques for applications for hydrogeological purposes. The results of the geophysical survey carried out in selected sites allowed to locate groundwater-rich zones, to establish the depth of occurrence of hard low permeable rocks, as well as to confirm the presence of faults.

Integration of ERT, IP and SP Methods in Hard Rock Engineering

Investigation of a hard rock site for the development of engineered structures mainly depends on the delineation of weathered and unweathered rock, and the fractures/faults. Traditionally, borehole tests are used in such investigations. However, such approaches are expensive and time-consuming, require more equipment, cannot be conducted in steep topographic areas, and provide low coverage of the area with point measurements only. Conversely, geophysical methods are non-invasive, economical, and provide large coverage of an area through both vertical and lateral imaging of the subsurface. The geophysical method, electrical resistivity tomography (ERT), can reduce a significant number of expensive drilling tests in geotechnical investigations. However, a geophysical method alone may provide ambiguity in the interpretation of the subsurface, such as electrical resistivity cannot differentiate between water and clay content. Such uncertainty can be improved by the integration of ERT with induced polarization (IP). Similarly, self-potential (SP) can be integrated with other geophysical methods to delineate the groundwater flow. In this contribution, we integrated three geophysical methods (ERT, IP and SP) to delineate the weathered and unweathered rock including the weathered/unweathered transition zone, to detect the fractures/faults, and to map the groundwater flow. Based on ERT, IP and SP results, we develop a geophysical conceptual site model which can be used by site engineers to interpret/implement the findings for build-out. Our approach fills the gaps between the well data and geological model and suggests the most suitable places for the development of engineered structures in the hard rock terrains.

Study of Fluid Flow Movement by Using Self Potential Data

The Self-Potential (SP) method is passive method in geophysics which works based on the natural presence of an electric field on the surface due to anomalies below the surface. SP value on surface can be generated by fluid flow through rock pores or fractures. We study fluid flow movement in subsurface using the velocity value of fluid flow derived from SP values measured on surface. For that purpose, we carried out mathematical modelling, connecting the Helmholtz-Smoluchovsky’s electrokinetic potential gradient equation with Darcy’s law. The velocity of fluid flow depends on the intrinsic permeability of rocks, electrokinetic potential gradient and electrohydrolic conductivity constant. We tested derived velocity of fluid flow on the SP data from a pilot project test site. Study results show that fluid flow in vertical direction can be identified from SP data at locations where there are significant changes of positive and negative SP values. Fluid flows from a high SP value to a low SP value and this flow is opposite the positive SP gradient. The SP value at study site lie in the range -80mV to -160mV, whereas the value of the water flow velocity lie in the range 0.08 cm/s - 0.21 cm/s.

Experimental Study on the Streaming Potential Phenomenon Response to Compactness and Salinity in Soil–Rock Mixture

The study on the effect of material structure and solution properties on the streaming potential of the soil–rock mixture (SRM) will be beneficial for improving the reliability of the measurement results for self-potential monitoring in embankment dams. We design two experimental groups and investigate the changes of potential and pressure during seepage of SRM (slightly clay materials) with different compactness and different concentration. The effects of the compaction degree and solution concentration on the streaming potential coupling coefficient and streaming potential were analyzed. The test results demonstrate that when the clay content in soil matrix is slight, the potential has a linear relationship with the hydraulic head difference, and seepage obeys Darcy’s law. The surface conductivity is negligible at 0.01 M (1 M corresponds to a concentration of 58.4 g L−1) salinity, the compactness of the SRM decreases (the permeability coefficient increases), the apparent streaming potential coupling coefficient and pressure difference decrease is the reason streaming potential decreases. The permeability coefficient of the SRM is not affected by the change in salinity (0.0001–1 M) at 85% compactness, and its seepage characteristics are related to the mineral composition, morphology and the thickness of the bound water layer (electric double layer). This study lays a foundation for further research on the self-potential method to monitor the structure of embankment dams.

Groundwater flow monitoring using time-lapse electrical resistivity and Self Potential data

Groundwater flow monitoring is crucial to groundwater management and pollution control. Traditional in-situ hydrological surveys monitor groundwater flow, pressure or temperature changes to infer the actual conditions of the underground, but there are characteristics of stratum destructiveness and difficult to obtain the regional variation characteristics of groundwater. Compared with geophysical methods, it has the advantages of non-destructive detection and regional quantitative interpretation, and indirect understanding of the physical properties of underground media and groundwater. In this paper, we combine the time-lapse electrical resistivity (ERT) and self-potential (SP) methods to monitor the groundwater flow. The ERT result establishes linkages between the resistivity and porewater content of the underground space, and captures the difference in resistivity through the change of underground water content. The SP method provides a direct way to predict groundwater flow according to its movement characteristics. Then, the joint resistivity and potential field are further used to estimate the soil's apparent-permeability. We carry out a real pumping experiment at a hydrological observation site to verify the proposed method. The time-lapse ERT and SP results reveal a significant increase in resistivity but a decrease in permeability during water pumping and groundwater recharge, representing the process of groundwater decline and recovery. The results also matched well with the groundwater level in-situ hydrological data. The study demonstrates that the joint ERT and SP data can provide a direct and reliable way to monitor groundwater flow or other time-lapse hydrogeological surveys in the vadose zone.

GROUNDWATER POTENTIALS ESTIMATION USING SELF-POTENTIAL METHOD AS AN EARLY PREDICTION OF LAND SUBSIDENCE IN GAMPONG LENGKONG LANGSA CITY

The Self-Potential (SP) method was used to identify changes in the potential groundwater in the area of Gampong Lengkong, Langsa City. The data acquisition technique was carried out with a fixed base technique with a measurement count of four acquisition line. Research is conducted for two months that July and August are the same in order to monitor the changes in the SP value associated with the change of SP anomaly. Interpretation is done qualitatively and quantitatively. Qualitative interpretation through analysis maps of the isopotential contours compared between the first month and the second month of measurements in the field. The interpretation is quantitatively by assuming the source of the subsurface anomaly fix geometry models of cylinders or sphere is done by the inversion modeling using the Levenberg-Marquardt method. The results showed that there was a reduction in SP value in the second month, indicating the potential shortage of groundwater in the region. The decrease in groundwater potential is also shown in the inversion results where the result of the calculation of SP anomaly source parameters in the first month is estimated to be at 7.77 meters to 11.05 meters below the ground in the monthly measurements second.

Measurement of unsaturated meltwater percolation flux in seasonal snowpack using self-potential

AbstractThis paper presents a feasibility study of in situ field measurements of unsaturated meltwater percolation flux within the vertical profile of a snowpack, using the self-potential (SP) method. On-site snowmelt column tests calibrated the SP measurements. The SP data measured electrical field strength with an electrode spacing of 20 cm, and coincident water saturation (Sw) measurements using time domain reflectometry allowed calculation of SP-modeled vertical percolation flux (qsp), expressed as Darcy velocity. The results reflected transient diurnal snowmelt dynamics, with peak flux lagging arrival of a saturation wetting front. Peak dailyqspwas 60 to >300 mm d−1, whereas daily snowmelt was 20–50 mm w.e. Surface refreezing events appeared to cause upward flow, possibly representing water redistribution toward the freezing boundary. Calculated fluxes were comparable to actual fluxes, although average errors ranged from −15 to +46% compared to average of melt expected from surface energy-balance and ablation stake measurements. By advancing method development to measure unsaturated meltwater percolation flux in snowpacks this study creates opportunities to study fundamental snowmelt processes, may improve mathematical modeling and may supplement glacier mass-balance studies and studies of snowmelt interactions with avalanches, groundwater and surface water.

Geophysical investigation and monitoring of dam infrastructure

Non-invasive, geophysical investigation of dam structures has been utilised by the geoengineering sector for decades. TerraDat has over 25 years of experience of carrying out geophysical surveys and has a good understanding of both the successes and limitations of the various techniques. More recently, there has been demand to not only determine the existence of leaks or structural defects, but also to monitor such features over time and provide information about the composition and condition of all the structural components at reservoirs. This paper reviews the ground-based geophysical methods, which are most widely used to investigate dams and spillways, and presents case studies of their effective use. The paper also presents the results from a new real-time monitoring system for the detection of leaks using the self-potential method to identify subsurface water flow.

Detection of Preferential Water Flow by Electrical Resistivity Tomography and Self-Potential Method

This study explores the hydrogeological conditions of a landslide-prone hillslope in the Upper Mosel valley, Luxembourg. The investigation program included the monitoring of piezometer wells, hydrogeological field tests, analysis of drillcore records, and geophysical surveys. Monitoring and field testing in some of the observation wells indicated very pronounced preferential flow. Electrical resistivity tomography (ERT) and self-potential geophysical methods were employed in the study area for exploration of the morphology of preferential flowpaths. Possible signals associated with flowing groundwater in the subsurface were detected; however, they were diffusively spread over a relatively large zone, which did not allow for the determination of an exact morphology of the conduit. Analysis of drillcore records indicated that flowpaths are caused by the dissolution of thin gypsum interlayers in marls. For better understanding of the site’s hydrogeological settings, a 3D hydrogeological model was compiled. By applying different subsurface flow mechanisms, a hydrogeological model with thin, laterally extending flowpaths embedded in a porous media matrix showed the best correspondence with field observations. Simulated groundwater heads in a preferential flow conduit exactly corresponded with the observed heads in the piezometer wells. This study illustrates how hydrogeological monitoring and geophysical surveys in conjunction with the newest hydrogeological models allow for better conceptualization and parametrization of preferential flow.

Review of Processing and Interpretation of Self-Potential Anomalies: Transfer of Methodologies Developed in Magnetic Prospecting

The self-potential (SP) method is one of the most inexpensive and unsophisticated geophysical methods. However, its application is limited due to the absence of a reliable interpreting methodology for the complex geological-environmental conditions. To exclude disturbances appearing in the SP method, a few ways for their removal (elimination) before quantitative analysis are presented. A brief review of the available interpretation methods is included. For the magnetic method of geophysical prospecting, special quantitative procedures applicable under complex physical-geological environments (oblique polarization, uneven terrain relief and unknown level of the normal field), have been developed. The detected common peculiarities between the magnetic and SP fields make it possible to apply the advanced procedures developed in magnetic prospecting to the SP method. Besides the reliable determination of the depth of anomalous targets, these methodologies enable the calculation of the corrections for non-horizontal SP observations and to determine the orientation of the polarization vector. For the classification of SP anomalies, is proposed to use a new parameter: the ‘self-potential moment’. The quantitative procedures (improved modifications of characteristic point, tangent techniques and the areal method) including the determination of the SP vector and SP moment, have been successfully tested on models and employed in real situations in mining, archaeological, environmental and technogenic geophysics. The obtained results indicate the effectiveness of the presented methodologies.

Numerical Modeling of Marine Self-Potential from a Seafloor Hydrothermal Ore Deposit

The redox field generated by electrically conductive minerals is one of the main constituents of self-potentials. It can be explained by electrochemical reactions in which conductors participate. The location and outline of seafloor hydrothermal ore deposits can be detected using marine self-potential anomalies that can be approximated through a marine geobattery model. The numerical modeling of marine self-potentials could be the foundation of corresponding data inversion and interpretation and improving the application effect of the self-potential method in detecting seafloor hydrothermal ore deposits. In this study, the inert electrode model and the on-land geobattery model are introduced to build the marine geobattery model, and the finite-infinite element coupling method is derived to deal with the truncated boundary problem effectively. Also, two tests are conducted to study the effect of model parameters on ground self-potential anomalies. A seafloor sulfide deposit model is built to study the self-potential characteristics. The numerical modeling results suggest that the precision and efficiency of the coupled method are superior to that of the traditional finite element method. Self-potential anomalies are greatly affected by medium resistivity, complex terrain, and amplitudes of embedded redox fields. Gradient changes in embedded redox fields do not cause significant self-potential anomalies but lead to mutations of current sources. The self-potential anomaly from the sulfide deposit model shows that the self-potential method can be effectively used to explore seafloor hydrothermal deposits that accompany negative self-potential anomalies above the ore bodies. The coupled method is quite suitable for multi-source models such as self-potential models.