Electrical Prospecting Methods Research Articles

REGULARITIES OF CHANGE IN PROPERTIES OF THE ANISOTROPIC MEDIUM OVER
 HYDROCARBONS FROM SENSING MODES

The article discusses the analysis of the patterns of changes in the properties of an anisotropic medium over
 hydrocarbons from sounding modes when using frequency modulation of signals and mixed amplitude-frequency
 modulation. The components of the surface impedance of the medium above hydrocarbons were modeled. A study
 was carried out of the characteristics of the environment above hydrocarbon accumulations for frequency-modulated
 signals from the modulation index, the frequency ratio coefficient and the conductivity of the dielectric filler
 of the host rocks. For amplitude-frequency modulated signals, the amplitude and phase characteristics of the combinational
 components of electromagnetic waves with two types of circular polarization are analyzed. Recommendations
 are given for the development of methods for searching for hydrocarbons based on frequency-modulated
 and amplitude-frequency-modulated signals. Methods for increasing the information content of electromagnetic
 methods of electrical prospecting are shown. The research results are relevant for geological exploration work.

Application of electrical prospecting methods for technogenic bodies (stored wastes of the mining industry) studies: review

The world experience of using electrical exploration methods in the study of technogenic bodies is considered, in particular: determining the zoning of tailings, groundwater migration routes and the stability of dams. The ongoing research demonstrates the high efficiency of combining the methods of geophysics, geochemistry, and hydrology. On the example of mining dumps located on the territory of the Kemerovo region and the Republic of Tyva, the achievements of the interdisciplinary team of the IPGG SB RAS are shown. The use of electrical resistivity tomography and magnetic prospecting in combination with geochemical mapping and gas survey made it possible to reveal the internal structure of tailings and dumps, outline watered horizons, and determine the transport of highly mineralized solutions to groundwater. Obtained results became the basis for creating a methodology for a comprehensive study of tailings and dumps, assessing the danger of technogenic bodies, and developing methods for minimizing their impact on the environment and the population of settlements.

Geometric 2.5D inversion of marine time domain electromagnetic data with application to hydrocarbon deposits prospecting

To solve the problem of detection and delineation of marine hydrocarbon deposits located at different depths in an inhomogeneous medium, we propose an approach to 2.5D inversion of electromagnetic (EM) data measured in the time domain (TD) using a differentially normalized method of electrical prospecting. The approach is based on geometric inversion, in which block structures are used to parameterize the geological medium. The sizes of blocks in the initial model are set depending on the depth. Bathymetry is taken into account as a 3D surface. As a result of inversion, the coordinates of block boundaries and conductivity inside blocks and layers are determined. The minimized functional is represented as a sum of weighted residuals between computed and practical data and regularizing terms. Adaptive regularization is used to satisfy parameter constraints. To solve a 3D forward problem and calculate derivatives with respect to parameters, the finite element method (FEM) is used. We propose to use a priori data on the depth of the target layers and use various options of block structures with an analysis of possible uncertainties in detecting target bodies and determining their boundaries. We present the results of a 2.5D inversion of field data obtained in one of the areas in the North Sea. Target bodies discovered as a result of inversion are confirmed by well data. Coincidences were obtained both for productive wells and for dry ones. Using synthetic data for various geoelectric models and options of block structures, we justify the proposed approach to the inversion of marine TD EM data and make recommendations for its use.

On the possibility of using the methods of geophysical electrical exploration for current control of the quality of soil processing

Purpose. Improving the quality of tillage by creating an indicator of current control to be installed at the machine-tractor unit. Methods. Based on the analysis of methods of geophysical research of the earth’s crust, a method of current control of soil cultivation during technological operations is proposed. Results. Variants of block diagrams of integral indicators of the quality of execution of technological processes of soil cultivation using methods of geophysical electrical prospecting are proposed. Conclusions 1. To ensure the quality of soil cultivation, it is necessary to use continuous current control methods. 2. It is expedient to create an indicator of integral soil tillage quality control for installation on existing machine-tractor units using the existing theoretical developments of geophysical electrical prospecting. 3. Modern means of measuring and processing the results allow creating indicators of the current integrated quality control of soil cultivation. Keywords: machine-tractor unit, quality, tillage, geophysics, electric survey.

Three-Dimensional Image of Crustal Density Model: A Case Study in South Kamchatka

Abstract —The methodology for building a 3D density model of the Earth’s crust and upper mantle for a crustal block in the South Kamchatka Peninsula is presented. The model is derived from the interpretation of the Bouguer anomaly values and data obtained by deep seismic soundings and electrical prospecting methods. 3D image creation can be viewed as a several phase procedure. At the first step, the area of interest is investigated through a network of intersecting profiles utilized for subsequent modeling depth density sections using the parameter scanning procedure. The a priori data include materials of geophysical surveys and geological, and petrophysical studies as well as results of depth estimation at singular points by the Euler deconvolution method. The next step involves formation of a 3D density matrix from the cross-section models. Coordinates in the cross-section planes are defined in the square grid nodes and converted to plane rectangular coordinates (the SK-42 reference system). A file of the cross-sectional database of density values is thus produced. For area shaving a sparse network of cross-sections, an additional database is derived from grid files of densities mapped horizon-wise. This ultimately results in the creation of the unified databases. A 3D network of cubic unit cells for three-dimensional (voxel) representation of density of the geologic medium is calculated. The model of density of unit cube with edge measuring 4 km was constructed for entire investigated block of the Earth’s crust. The model was detailed by decreasing successively the unit cube edges to 2.0, 1.0, and 0.5 km. The 3D modeling results are presented as block diagrams and density isosurface maps in horizontal slices at different depths. The block diagrams show isosurfaces with densities typical of deep subsurface boundaries and structures. The isosurfaces for densities of 2.75 and 2.90 g/cm3 reflect the morphology of the roof of the crystalline basement, and the lower–upper crust boundary, respectively, while the isosurfaces of 3.20 and 3.33 g/cm3 represent feasible shape of the crust–upper mantle contact. The lower-density zone ubiquitously observed in the investigated crustal block is caused by rock destruction along the deep fault. It is identified in the model with 1 km cubic unit cell side and encompasses the feeding systems of volcanoes, namely: Sopka Asacha (Asacha Volcano), Mutnovskaya Sopka (Mutnovsky Volcano), Gorelaya Sopka (Gorely Volcano), and Vilyuchinskaya Sopka (Vilyuchansky Volcano).The model with a 0.50 km cubic unit cell side shows a 2.85 g/cm3 isosurface, which delineates a column-shaped high-density region. A higher density revealed in the block is assumed to be associated with basite intrusions. 3D density models based on cross-section modeling provide additional information for geodynamic reconstructions, allowing a rough estimation of the geometry of concealed geologic features and their volumes, and can be utilized in 3D modeling to build initial models.

Geoelectrical structure and monitoring in fault zones of Uimon depression in Gorny Altai region using electromagnetic methods

In this paper we present the results of our studies of sections of the Uimon basin in Gorny Altai (Russia) using a complex of electrical prospecting methods. The areas of Baratal Formation at the surface have been investigated. This areas explored in order to understand the stages of formation of the depression. In addition, the possibilities of the electrotomography method for regular observations in seismoactive regions are shown. Comparison of the amplitudes of the resistivity variations based on repeated ERT measurements in different zones of the Terekta fault indicates the activity of its eastern part, which is expressed in significant resistivity variations exceeding 100%. At the same time, the variations in the northwestern part of the fault, reaching 15% on average, are many times smaller.

SOME PROBLEMS OF ELECTRICAL GEOPHYSICAL PROSPECTING METHODS USED FOR EXPLORATION OF ORE DEPOSITS

Electrical geophysical prospecting methods are widely used at different stages of geological exploration. In the last two decades, new computer technologies and satellite navigation systems were successfully introduced in the geophysical industry. As a result, exploration technologies have improved, and new geophysical methods have been developed, such as electrical resistivity tomography (ERT) and spectral induced polarization (SIP) methods. An important role in ore geophysics is played by magnetotelluric (MT) methods. In this article, we focus on the issues of methodology and interpretation of electrical prospecting data for solving ore exploration problems. Special attention is paid to the induced polarization (IP) method that is most widely used in mineral exploration and mining industry as one of the most important and most dynamically developing techniques of ore geophysics. In addition, the issues of correct choices of survey scales and the use of automatic 2D and 3D inversion programs are considered.

Application of Pseudo-random electrical exploration method in mineral exploration: a case study of skarn-type ore body

Skarn-type ore body containing rich mineral resources, which is a type of deposit with important industrial significance and a wide distribution, is formed by metasomatism of mineral gas-bearing hydrothermal fluids on or near the contact zone between intermediate-acid-medium-basic intrusive rocks and carbonate rocks. It is hard to obtain stable data by using conventional electrical prospecting method because of strong electromagnetic interference. A new pseudo-random method is used to do geological survey work in Northeast China for interference avoidance.

FIRST RESULTS OF STUDIES IN THE GORLOVSKAYA VALUES BY GROUND METHODS OF ELECTRIC EXPLORATION WITH CONTROLLED SOURCES

The article presents the first results of the study of the Gorlovskaya depression in the area of coal deposits of the Novosibirsk region by methods of ground electrical prospecting using transient electromagnetic sounding and electrical tomography. Near-surface models were obtained to depths of 100 m, as well as deep geoelectric characteristics of the sedimentary filling of the depression and the eastern fault boundary.

Prediction of marginal rock mass stability in clays of Quaternary deposits including the effect of filtration reservoir by the example of the Bachat coal mine

Introduction. During opencast mining, the development of mine workings in clays of Quaternary deposits is often accompanied by stability loss. As a rule, the reason for the development of geomechanical processes 46 "Izvestiya vysshikh uchebnykh zavedenii. Gornyi zhurnal". No. 3. 2021 ISSN 0536-1028 is the mismatch between the accepted geometry and physical-mechanical characteristics of soils. In case strength characteristics and moisture content are strongly related in the conditions of lacking water saturation sources, slopes remain stable for a long time. However, in the case of water saturation, soils change to plastic or liquid consistency, and the strength properties are reduced. In engineering practice, to prevent hazardous geomechanical processes, electrophysical methods are applied that make it possible to build the boundaries of soil moisture anomalies through electrical contrast. In the instances when the water-saturated strata occurrence depth and thickness is known from drilling and vertical electrical sounding data, electrical profiling makes it possible to promptly determine the variability of these characteristics of the anomaly. The authors proposed an algorithm of water-saturated strata thickness variability determination from the point of electrical profiling. Research aim is to predict the stability of the marginal rock mass in clays of Quaternary deposits, taking into account the effect of filtration reservoirs by combining engineering-geological databases and geophysical measurement results based on the 3D geological-geophysical model. Methodology includes the analysis of the engineering-geological databases and geophysical measurement results. Results. A 3D geological-geophysical model of the marginal rock mass with the boundaries of the watersaturated stratum was built from the results of the research to predict the stability of the marginal rock mass’s actual position. Slope stability analysis established the following: at design sections О3у3–О5у5 after deformation, retaining forces exceed shearing forces significantly (safety factor) because the weight of the base wedge grows due to landslide masses; potential landslide hazard area is associated with the design section О1у1, which is due to smooth fall of the stability factor from 1.38 (section О2у2) to 1.06, close to ultimate. Conclusions. For the extension of the marginal rock physical-mechanical properties variation it is appropriate to apply the method of electrical prospecting (sounding and profiling) determining watersaturated areas by local negative anomalies of effective electrical resistivity and establishing the function of loose Quaternary deposits thickness variation by the inversion of electrical profiling graphs with the use of the least square procedure and the golden section method. If landslide hazard areas are vast, the variation of the stability factor design values, which were determined based on 3D geological-geophysical models, may possess the non-monotonic character with several extreme values and significant gradients. For that reason, it is appropriate to carry out computerized analysis with a cyclic extension of the most hazardous areas by the coordinate of the profile and the direction of the design section in a plan.

Detection of zones of soil contamination with contrast-in-resistivity ecotoxicants by profiling

A method for detecting zones of soil contamination with contrast-in-resistivity ecotoxicants, as well as geophysical methods for monitoring soil decontamination processes, are discussed in the article. A zone of soil contamination was designed and simulated using electrical prospecting methods - sounding and profiling. The direct and inverse problem of electrical prospecting of a contaminated zone in the form of a sphere inside a homogeneous soil body was solved in this work, while the main design dependencies were determined, which most accurately describe the data obtained experimentally. The proposed algorithm, based on adaptive step size random search, allows to quickly determine the depth and the effective radius of a zone of contamination with contrast-in-resistivity ecotoxicants, based on the results of profiling, and to estimate the degree of pollution by the ratio of the resistivity of the anomalous zone to that of the host medium.

Physical modeling of the Bazhenov formation in combination with CSEM and seismic methods

To predict the properties of the Bazhenov formation and to identify the areas in which oil deposits are localized the use of electrical prospecting methods is promising. The main goal of the current research is to evaluate the effectiveness of using Controlled Source Electro Magnetics (CSEM) exploration for the area forecast of the properties of the Bazhenov formation. The main objectives of physical modeling in this research are: Creation of an isotropic physical model corresponding to the electrical and elastic parameters of the section of the studied area, and performing 3D modeling on it with survey parameters that reproduce real seismic and CSEM surveys To convince that the contrast of the elastic properties and the ratio of the resistivity of the target interval of the Bazhenov formation and overlying rocks in the created physical model corresponds to the real petrophysical characteristics of the section of the studied area; Obtaining initial data for testing algorithms for synchronous inversion of seismic + electric and testing various approaches to processing and interpretation of CSEM and 3D seismic data.

The role of electromagnetic sounding in the assessment of hydrothermal resources of the Northern Tien Shan

This work presents the results of the electromagnetic study of thermal water deposits, conducted in the territory of the Bishkek geodynamic test area (Northern Tien Shan). The heat flow in this territory is quite high, which testifies in favor of the development of geothermal energy in the region. The objects with high electrical conductivity isolated in the geological environment by various electrical prospecting methods are fractured basement rocks saturated with a heated fluid (in a different aggregate state) in the upper part of the Earth’s crust, promising for the development of geothermal energy.

Geophysical survey of earthen dam using the electrical prospecting methods

The hydraulic structures for the land reclamation needs and their operation are the objects of careful attention. The water-bearing earth dams of small height pose an extra danger, where the accident occurs the most often. Such facilities should be constantly monitored to prevent the dangerous incidents. The article discusses an alternative method for studying the filtration properties of earth dams by the electrical parameters – resistivity, induced polarization and self-potential. The relative polarizability was used to exclude the influence of electrical resistivity to the induced polarization data. A study of advanced technology to identify the filter zones was carried out on an earthen dam in the Almaty region, Kazakhstan. The measurement data for three profiles are presented as the sections form in the parameters of resistivity and relative polarizability. Their complex interpretation with the respect of self-potential data, is given as a diagram of probable filtration paths. This is possibly due to the local increased watering in the dam loamy body. Then, the electric and self-potential parameters were evaluated to determine the filtering zones. The study results of above parameters have identified several water-saturated zones in the dam body. This technology could be used to estimate the condition of such objects and their engineering-geological monitoring.

ЭКСПЕРИМЕНТАЛЬНЫЕ ИССЛЕДОВАНИЯ ЭФФЕКТА ХОЛЛА В ЗЕМЛЕ ПРИ ЗОНДИРОВАНИЯХ СТАНОВЛЕНИЕМ ПОЛЯ В БЛИЖНЕЙ ЗОНЕ

В период с 8 по 15 июля 2018 года сотрудниками Лаборатории геоэлектрики ИНГГ СО РАНпроводились полевые исследованияв рамках гранта РФФИ № 17-05-00083 А. Исследования направлены на обнаружение и численную оценку эффекта Холла в геологических средах. Этот эффект должен очень слабо проявляться во всех сигналах электромагнитных зондирований. Комплекс электроразведочных методов был выбран в связи с методической эффективностью и относительной простотой выполнения работ.Задачи исследований:выбор участка работ; измерение четырьмя радиальными линиями MN сигналов зондирований становлением в ближней зоне для регистрации компоненты , вызванной эффектом Холла; измерение линией компоненты для контроля измерений. Актуальность исследованияобусловлена в первую очередьтем, что гальваномагнитные эффекты (в т.ч. и эффект Холла), возникающие в скрещенных электрическом и магнитном полях, хорошо известны в физике, но не исследовались применительно к геологической среде – это значит, что данные эффекты пока неучтенным образом влияют на сигналы в геоэлектромагнитных зондированиях. Цель: обнаружение эффекта Холла в геологических средах. Объект: эффект Холла в геологической среде. Методы: зондирование становлением поля в ближней зоне, магнитотеллурическое зондирование. Результаты. Полевые исследования в 2018 г. являются первыми целенаправленными полевыми исследованиями с целью обнаружения эффекта Холла в геологической среде методами электромагнитных зондирований. Цель работ, по мнению самих исследователей, по предварительным данным, достигнута. Получена оценка холловской проводимости ~1–2·10–3 См/м.

Electrical Prospecting Methods for Advance Detection: Progress, problems, and prospects in Chinese coal mines

Around 1985, there were 20 serious flooding accidents in Chinese coal mines that caused heavy casualties and property losses. As a result, geophysical mine-prospecting technologies for predicting geological hazards have attracted increasing attention.

The Borehole-Ground Controlled Source Electromagnetic Signal Recorder

As a high-tech method of electrical prospecting, borehole-ground controlled source electromagnetic imaging is aimed to enhance the detection depth and increase resolution appropriately. It requires the signal recording instrument to be a ground and underground (pit, wells) quasi-three-dimensional receiver. To record signals of the natural field and controlled source from 0.1Hz to 20KHz in N * 10nV - N * 100mV amplitude range, we used a series of new technology, such as ARM + LINUX embedded, low-noise high-precision, GPS synchronization and low drift, low-power, NET, high-capacity storage, to develop a borehole-ground controlled source electromagnetic recorder with large dynamic range of broadband. Field survey data indicate that this signal recorder can work in a normal and stable manner, and all expected technical indexes have been largely reached.

Study of geological conditions in coal fields in the southern Far East of Russia by electrical prospecting methods

Study of geological conditions in coal fields in the southern Far East of Russia by electrical prospecting methods

Application of electrical prospecting methods to petroleum exploration on the northern margin of the Siberian Platform

This paper considers the potential of modern electrical prospecting methods for evaluating oil and gas occurrence on the northern margin of the Siberian Platform—a vast region from the Gydan Peninsula to the mouth of the Lena River. Results of regional electrical surveyes over the past 12 years in this region are generalized. The capabilities of electrical prospecting for solving the following four problems are defined: survey, in conjunction with seismics and drilling, in the Jurassic-Cretaceous part of the section; study of the structure of the Paleozoic sequence; study of the junction zones of large geoblocks and deep structure of the Earth’s crust and upper mantle; and study of the permafrost. © 2018, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

GEOPHYSICAL STUDIES OF SUBSURFACE GAS SEEPAGE IN SAND-CLAY SOILS

The article describes the results of new engineering-geophysical and geomorphological studies focused on searching for subsurface gas accumulations. The methods of seismic refraction and electrical prospecting (electrical resistivity tomography) were used. The possibilities of these methods are shown in the study of such deposits. Studies were carried out at the site of the proposed construction within the lowlands of the BalticLadoga clay. In the course of engineering and geological drilling, short-term emissions of water, sand and gas to a height of 5 m were recorded, during the drilling operations and gas emissions from wells continued for a year. Through the site there is an erosion ledge dividing the drilling site into two subhorizontal levels. Due to geophysical and geomorphological data we can reveal on the site two strata: the upper level is the Valdai glacial deposits and the lower one is a marine (littoral) terrace. The different origin of these strata is confirmed by distinct seismic characteristics and types of geoelectrical sections, as well as by the results of engineering-geological drilling. We propose the contiguity boundary to be directly under the ledge; however, the details of the studies were not sufficient to determine the quantitative parameters of the contiguity boundary. Our data analysis made it possible to isolate gas-saturated sand-clay lenses in the section and to outline the mapping features of gas-saturated soils distributed within the study area. For gas-saturated soils, relatively high values of specific electrical resistances and P-waves velocities, a decrease in the Vs/Vp ratio and lenticular form of geophysical anomalies are characteristic here. The origin of gas accumulations comes from organic saturated with marine sediments in the littoral layer.