Geophysical Methods Research Articles

Результаты определения коэффициента пористости в нефтенасыщенных глинистых породах

The article studies the wells that opened clayey reservoirs of Paleogene age. When predicting the trajectory of a crack during hydraulic fracturing (HF), it is necessary to take into account the percentage of minerals in the rock, since cracks during hydraulic fracturing are formed at the contacts between mineral grains. This conclusion is indisputable, but obtaining complete information about the percentage of minerals in a rock is an expensive and not always feasible task. At the same time, the physical and mechanical characteristics of clayey rocks are no less significantly influenced by their porosity. Therefore, it is important to note that a reliable determination of the porosity coefficient from the exposed geological section will undoubtedly have a primary positive impact on the reliability of hydraulic fracturing modeling. Based on this, in wells that opened clayey reservoirs, the values of porosity coefficients determined by various methods were analyzed, including the direct one – analysis of core, cuttings and the indirect one – geophysical methods. During the work, a coincidence of the porosity coefficient in the core, cuttings and electrical logging was discovered. Based on the results of the study, it can be concluded that the porosity coefficient determined from acoustic logging (AL) significantly exceeds the values of the porosity coefficient determined from core, cuttings and induction logging. This is due both to the influence of clay content on the acoustic logging readings, and due to the low quality of AC materials induced by erosion of the wellbore. It should be noted that the calculations of porosity coefficients in the above-reference part – in the Batalpashinsky formation based on core and induction logging – coincide almost completely. However, in the sub-reference part of the formation the readings differ slightly. The porosity coefficient calculated is a maximum of 2% lower than the porosity coefficient determined from the core, which is quite acceptable.

Bayesian Inversion, Uncertainty Analysis and Interrogation Using Boosting Variational Inference

AbstractGeoscientists use observed data to estimate properties of the Earth's interior. This often requires non‐linear inverse problems to be solved and uncertainties to be estimated. Bayesian inference solves inverse problems under a probabilistic framework, in which uncertainty is represented by a so‐called posterior probability distribution. Recently, variational inference has emerged as an efficient method to estimate Bayesian solutions. By seeking the closest approximation to the posterior distribution within any chosen family of distributions, variational inference yields a fully probabilistic solution. It is important to define expressive variational families so that the posterior distribution can be represented accurately. We introduce boosting variational inference (BVI) as a computationally efficient means to construct a flexible approximating family comprising all possible finite mixtures of simpler component distributions. We use Gaussian mixture components due to their fully parametric nature and the ease with which they can be optimized. We apply BVI to seismic travel time tomography and full waveform inversion, comparing its performance with other methods of solution. The results demonstrate that BVI achieves reasonable efficiency and accuracy while enabling the construction of a fully analytic expression for the posterior distribution. Samples that represent major components of uncertainty in the solution can be obtained analytically from each mixture component. We demonstrate that these samples can be used to solve an interrogation problem: to assess the size of a subsurface target structure. To the best of our knowledge, this is the first method in geophysics that provides both analytic and reasonably accurate probabilistic solutions to fully non‐linear, high‐dimensional Bayesian full waveform inversion problems.

GPR snow cover investigation to determine its spatial and temporal variability

The paper presents data on the meteorological features of the 2023/24 winter season in Moscow and the results of observations of snow cover at the MSU meteorological observatory site, as well as a comparison of these meteorological conditions and the characteristics of snow accumulation in the winter of this year with previous years. The paper also presents the methodology and data of ground penetrating radar sounding of snow cover at the site of the Moscow State University meteorological observatory, their analysis and comparison with the given direct measurement data, which allows us to draw conclusions about the structure of the snow layer and its spatio-temporal variability based only on geophysical methods.

Wastewater leakage identification in WWTP and concrete pipelines using integrated geophysical imaging methods

Industry and mining activities covers a broad spectrum of processes that dispose an abundant amount of wastewater. Given the vast array of industries, there are equally large number of heavy metals, organic solvents, and hydrocarbons pollutants associated with its wastewater, posing a great threat to aquifers, especially groundwater. Main contributor of this polluting scheme are from the leakage of underground/surface storage tanks, effluent pipework, industrial sewers, and waste injection system. To ascertain the presence of pollution in the subsoil and groundwater resources, an integrated geophysical method can be the alternative of non-invasive methods. The presence of contaminants in subsoil alters the physical properties of rock formations and decrease pore-water resistance, therefore it can be mapped by geoelectrical resistivity. In this paper, study case was conducted in Medan Industrial Estate, Indonesia, to identify potential leakage under the Wastewater Treatment Plant (WWTP) and its pipework, using Geoelectrical Wenner and Magnetotelluric Method with 5 lines in the interval of 40-60 meters and Magnetotelluric Method throughout the 175 meters of pipework in the production area. Based on the Geoelectrical Method, an anomaly with a low resistivity value was detected within 7 meters of the ground depth. Meanwhile, in the Magnetotelluric Method, a moderate permittivity value was detected that is local and located within 2 meters depth which is where the pipe and the bottom of the WWTP storage tank is located. In conclusion, based on the results obtained from the Geoelectrical and Magnetotelluric Methods that have been carried out in the WWTP area and along the wastewater pipeline leading to the WWTP, no anomalies were found that lead to waste water leakage.

Balancing urban growth and the sustainability of groundwater and agricultural land: Case of the berrechid-settat area

Urbanization is an inevitable global phenomenon characterized by the exponential growth of urban areas in terms of both population and infrastructure. However, this rapid urban expansion often comes at a significant environmental cost. This article explores the multifaceted consequences of urbanization, shedding light on its role in contributing to desertification, compromising water quality, and depleting groundwater resources. To assess the scale of urbanization’s impact, comprehensive landuse studies are crucial. Geographic Information Systems (GIS) and remote sensing techniques offer valuable tools for mapping and monitoring land-use changes over time. These methods enable the quantification of the conversion of agricultural land into urban areas and identify trends in urban sprawl, providing essential data for understanding the scale of the issue. Water quality assessments are equally vital; we can employ water sampling and laboratory analyses to quantify pollutant concentrations in urban runoff and groundwater. Monitoring the presence of contaminants such as oil, chemicals, and litter, as well as their effects on water quality; helps measure the environmental impact of urbanization. Groundwater studies can utilize hydrogeological investigations, including the use of monitoring wells and geophysical methods, to evaluate changes in groundwater levels and quality. These data are instrumental in gauging the depletion of groundwater reserves and their potential contribution to water scarcity issues. In conclusion, the consequences of urbanization extend far beyond the confines of urban areas, affecting agriculture, ecosystems, and water resources. As urbanization continues to advance, it is imperative to develop sustainable urban planning and management strategies that mitigate its environmental impact, preserve agricultural land, protect groundwater resources, and ensure the long-term health of the planet.

ПРИМЕНЕНИЕ МЕТОДОВ ИНЖЕНЕРНОЙ ГЕОФИЗИКИ ПРИ ОЦЕНКЕ ТЕХНИЧЕСКОГО СОСТОЯНИЯ СООРУЖЕНИЙ ИНЖЕНЕРНОЙ ЗАЩИТЫ ШАПСУГСКОГО ВОДОХРАНИЛИЩА

Purpose: to apply engineering geophysics methods based on the assessment of reliability parameters using non-destructive testing to identify the state of the engineering protection structures of the Shapsug reservoir. Materials and methods. The materials for the study were non-destructive testing data performed at different times of the year at the Shapsug reservoir, using “Oko-3” ground penetrating radar, “Pulsar-2.2” unit, Sokkia CX-105 total station, Nokta Invenio Smart and PSG-MG4 static action penetrometer. During the inspection, attention is drawn to the presence of such defects and damages as: violation of the geometric dimensions of the element or structure section; presence of deformation of an element or structure as a whole; formation and decompaction of the voids; landslide processes; visual dynamic damage; various cracks and the size of their opening; concrete and metal structures corrosion, etc. Results. The engineering-geophysical method for assessing the technical condition of the engineering protection structures of the Shapsug reservoir has been carried out. The state of the connection between earthworks and concrete structures and the temperature-sedimentation joints between concrete and reinforced concrete structures, affecting their stability, has been studied. Radiograms of collapse sites that arose as a result of accidents and were eliminated during the reconstruction of the dam were obtained. Conclusions. It was determined on the results obtained, that the geophysical complex makes it possible to study earthen low-head dams when determining various soil parameters, and most importantly, to identify the position and size of various defects inside the earth foundation of the dam. The identified difficulties were successfully resolved using a combined geophysical method, and the main problem is the compilation and adaptation of this method for a specific object.

Archaeological geophysical investigation of Uzun Rama Steppe kurgans, Goranboy

Geophysical methods can provide valuable information when imaging man-made subsurface structures prior to archaeological excavations. An archaeological geophysical survey was conducted on funeral chambers (also known as kurgans) from the Early Bronze Age, in the Shadili-Uzun Rama Steppe of the Goranboy region, near the Kurakchay river gorge in Azerbaijan. This multimethod survey is based on a ground-penetrating radar profile, heat map of the total magnetic intensity, and contiguous profiles of electrical resistivity and seismic refraction. Brief processing and default inversion methods enabled us to obtain geophysical images in accordance with the lithology (a subsoil comprised of alluvial-proluvial conglomerate terrasse). The shape of the kurgans was recovered mainly through electrical resistivity tomography, enabling future targeted excavations. Overall, this study further testifies that geophysics provides valuable information for archaeological investigations, although higher resolution could be achieved by using more advanced field methodology and processing.

The measurement and analysis of similarity degree on data from two types of seismic recorders

Seismic instruments are widely used in projects related to geophysical prospecting. Quality data from seismic recorders help to determine subterranean structures with high precision. This paper first introduces a field experiment carried out by deploying seismic stations equipped with two kinds of seismic recorders: GEI (China) and Reftek 130 (USA). Then, the three-component seismograms from GEI are measured and evaluated by comparing with those from Reftek 130 in different aspects: waveforms in time and frequency domain, quantitative analysis by calculation and statistic of correlation coefficient, and signal to noise ratio of seismic signal. Our results were presented by multiple images as the following: (I) Both the time and frequency waveforms of GEI were almost exactly coincident with those of Reftek 130, with over 98.60 percent of the correlation coefficients in the time domain within 0.95–1.0, and all those in the frequency domain above 0.9977. (II) The accurate time lag estimation of GEI’s signal was gained by the lag and correlation algorithms based on left–right sliding windows. The GEI clock was 7.3545 ns behind the Reftek 130 clock after every 1 s, which could be utilized to correct the internal clock to improve the synchronous accuracy of seismic recorders. (III) Some seismic signals from GEI were obviously stronger than those from Reftek 130. Our results may potentially promote and support the optimization of seismic recorders and their application in geophysics methods.

Application of Comprehensive Geophysical Rospecting Method in the Detection of Goaf in Shanxi Wuyang Coal Mine

Application of Comprehensive Geophysical Rospecting Method in the Detection of Goaf in Shanxi Wuyang Coal Mine

Characterisation of infiltration in the cave of Villars (Dordogne) by geophysical and isotopic methods: Importance for paleo-climatic studies based on speleothems and for the conservation of heritage sites

Characterisation of infiltration in the cave of Villars (Dordogne) by geophysical and isotopic methods: Importance for paleo-climatic studies based on speleothems and for the conservation of heritage sites

Small-strain stiffness of liquefiable sands: A comparison between bender elements and resonant-column tests

Soil stiffness can be estimated by geophysical and dynamic testing methods. In the laboratory, the most common methods to measure the small-strain stiffness are the bender elements (BE) and resonant-column (RC) tests. This paper focuses on the comparison between the results of the small-strain stiffness of sands by BE and RC tests. For this purpose, an experimental program involving three liquefiable sandy soils (i.e., NB, TP-Lisbon and Toyoura sands) was carried out. Such program covered the measurement of the small-strain stiffness of these soils by BE in triaxial and RC apparatuses for different mean effective stress conditions. All tests were carried out on saturated soil specimens, which were remoulded using the air pluviation method for various relative densities. The experimental results were interpreted in terms of shear-wave velocity (Vs) and maximum shear modulus (Gmax) to derive the stress-dependency laws of these parameters. The experimental results revealed differences between Vs obtained from BE and RC tests, evidencing a clear effect of relative density on the shear-wave propagation. However, such a variation may be significantly reduced when a normalisation of Gmax in terms of a void ratio function F(e) is applied. As a result, this study demonstrated and validated the importance of accounting for the soil state conditions, for adequate compatibility of BE and RC tests in the estimate of the small-strain stiffness of liquefiable sands.

ИССЛЕДОВАНИЕ СИГНАЛЬНОГО НАЛОЖЕНИЯ ГИДРАВЛИКИ В МОДЕЛЯХ ПУСТОТ КАК ОБОСНОВАНИЕ ЭЛЕКТРОМЕТРИИ ДЛЯ КАРТИРОВАНИЯ КАРСТОПРОЯВЛЕНИЙ

The study of the karst territories for their use for optimal placement of subsurface use facilities, as well as the construction of engineering structures on them, is an important geotechnological and operational task. Based on the calculation of the hydraulic parameters of the geological environment, the article shows that karst objects are the cause of the formation of drainage regime and water loss, up to the drainage of this environment. It has been established that even small sizes of karst voids lead to fluctuations in the level of deep waters (UGW) and the formation of aeration layers. It is determined that in watered, deep strata, exploration and monitoring of karst objects is sufficiently reliable, in combination with the analysis of measured filtration rates according to the hydraulic model, methods of resistivimetry and thermometry of wells provide. Whereas, when mapping karsts above the UGV and in the covering strata, it is advisable to rely on the identification of signal aeration and dehumidification of the medium using the electrometric method, based on the connection of models of hydraulics and fields of electrical conductivity. The principal possibilities of geophysical methods of karst mapping are considered. It is established that the depth and coverage of exploration should exceed the size of the focus of filtration disturbances in the studied arrays. It is shown that the registration of high-frequency signals does not allow to ensure the reliability of the assessment of karstological safety.

ОБ АКТУАЛЬНОСТИ И ВОЗМОЖНОСТИ ПРЕДУПРЕЖДЕНИЯ СЕЙСМИЧЕСКОЙ ОПАСНОСТИ НА ТЯНЬ-ШАНЕ

The problem of activation of the seismic regime of the Tien Shan and the possibility of strong earthquakes in its southern and northern foothills in the next few years in connection with the earthquake of January 23, 2024, which occurred in the southern foothills of the Central Tien Shan in Ushi County (Ukturpan) of Aksu Prefecture of Xinjiang Province of the People's Republic of China, an earthquake of magnitude 7.1 occurred near the city of Aksu. The Ushinsky earthquake of 23.01.2024 may mean the beginning of a new seismic activation of the Tien Shan. Here is the previous cycle of eight strongest earthquakes with M=6.9-8.3 in the northern and six with M=6.8-7.8 in the southern foothills of the Tien Shan, which lasted 100 years, began in 1885 with the Belovodsky earthquake (M=6.9 near Bishkek) and ended with the Kashgar earthquake (M = 7.0) in 1985. There was another strong Suusamyr earthquake with M = 7.3 in 1992 in the middle part of the Tien Shan, which is atypical in this region. With the earthquake of Usha, the period of calm for earthquakes with magnitudes 7.0 and more, which lasted for almost 40 years, ended. A brief overview of the current state of the issue of forecasting strong earthquakes is given. It is noted that there is a certain discrepancy between the basic concepts of the existing earthquake source models and the available geomechanical data on the fragile destruction of rocks. The latest achievements of tectonophysics in the field of studying the current stress state directly in rock massifs are presented. It is shown that, based on the results of tectonophysical reconstruction of natural stresses, it is possible to perform zoning of active faults according to the level of coulomb stresses responsible for the implementation of brittle fracture. The analysis of the results of active fault zoning performed in the foci of the strong Wenchuan earthquake (M=8.0, 2008) and the Karamushir earthquake (M=7.8, 2023) is given. The analysis of the possibilities for long-term and short-term forecasting based on a complex of seismic, seismotectonic and geophysical methods based on the results of tectonophysical zoning of active faults is performed.

Multiphysics for industrial gas exploration – The Fonts-Bouillants case study

Helium is key in numerous industrial sectors. Production in western Europe is still absent despite criticality of helium as a resource. 45- 8 Energy, implementing multiple geophysical methods in its Fonts- Bouillants exploration license, located in France, intended to couple geophysics with geological and geochemical information to characterize more accurately the subsurface before drilling. The area has been underexplored until license awarding in 2021 and therefore brand-new data acquisition was the only path to uncertainties reduction. A finely tuned acquisition campaign of electric resistivity tomography, reflection seismic, electromagnetic methods, followed by a thorough transverse interpretation phase, enabled 45-8 Energy to step up with a successful shallow drilling campaign. Geophysics was key to implement boreholes which turned out to be discoveries and key to unlock funds to build the first helium production unit in western Europe. Adventure shall continue with upcoming deeper drilling campaign, revealing full potential of the exploration permit by mid- 2024.

Application of geophysical methods in fine detection of urban concealed karst: A case study of Wuhan City, China

Application of geophysical methods in fine detection of urban concealed karst: A case study of Wuhan City, China

Natural Seismic Event Analysis Based on Signal and Source Characteristics from two Experiments in Antarctica.

This study presents geophysical data from two passive seismic measurements conducted at two different sites in Antarctica. We analyzed the signals mainly in the frequency domain through the multitaper method to extract some spectral characteristics of the signals that would have been out of reach through the usual FFT approach. The power spectral density of the signals carries information about the processes that generated them, allowing its correlation with their source origin and type, either natural or anthropogenic. We deal with three different source types: calving, wind, and anthropogenic origins. The former is closely related to glacier dynamics, being modulated by the prevailing atmospheric processes. At both locations the wind noise is prevalent, complicating the analysis of other events like calving. We have used data classification, estimation of the source azimuth, and seismic apparent velocity to demonstrate the viability of using geophysical methods to study glacier elastic parameters and dynamics. Moreover, the calving rate can yield a wider and more independent understanding of glacier hydrodynamics and may help to estimate the future response of the polar areas to a changing environment.

The effectiveness of very low-frequency electromagnetics (VLF-EM) method in detecting buried targets at a controlled site

The ever-increasing anthropogenic activities that pose a significant threat to environmental security and sustainability have spurred geophysicists to review enhance geophysical techniques for shallow geophysical investigations, especially in identifying illegal buried materials. This article applied very low-frequency electromagnetic (VLF-EM) at an experimental geophysical site (EGS) to examine the geophysical response over various buried targets. The VLF-EM data acquired on the site with and without buried targets demonstrate the nature of the anomalies and the characteristic signals of the buried targets. There are significant variations in the anomalies source-bodied between the site with and without buried targets. The result of the pre-burial investigation shows no major contrast in the equivalent current density values across the site without targets. Minors and major anomalies were encountered after burying the targets corresponding to the buried targets. Some signals become stronger over a large buried target. However, there were a few undetected targets and some cases of unsatisfied results, which were also discussed. The performance of the VLF-EM method in terms of depth estimation was also examined. A significant variation was noted due to the presence of the buried targets and it was noted that the current density seems to always emerge maximally and minimally around the conductor targets and non-conductive targets, respectively. The failure of the VLF-EM to detect the buried pipes in various orientations was examined. The VLF-EM method is more consistent at small spacing and it can be very useful for identifying underground metallic and non-metallic targets. The study successfully provides useful information to complement the complexity of the use of geophysical methods while enhancing the subsurface information and understanding of VLF-EM anomalies or responses generated by various targets such as subsurface geological structures, buried waste contaminants and underground utilities to boost environmental studies and engineering investigations.

Recharging of Groundwater by the Geophysical Method Based on Resistivity Meter, A Case Study of Naya Raipur, Chhattisgarh

Recharging of Groundwater by the Geophysical Method Based on Resistivity Meter, A Case Study of Naya Raipur, Chhattisgarh

Three-dimensional cooperative inversion of airborne magnetic and gravity gradient data using deep-learning techniques

Using multiple geophysical methods has become a prevailing approach in numerous geophysical applications to investigate subsurface structures and parameters. These multimethod-based exploration strategies have the potential to greatly diminish uncertainties and ambiguities encountered during geophysical data analysis and interpretation. One of the applications is the cooperative inversion of airborne magnetic and gravity gradient data for the interpretation of data obtained in mineral, oil and gas, and geothermal explorations. In this paper, a unified cooperative inversion framework is designed by combining the standard separate inversions with a deep neural network (DNN), which serves as the link between different types of data. A well-trained DNN takes the separately inverted susceptibility and density models as the inputs and provides improved models that will be used as the initial models of deterministic inversions. A two-round iteration strategy is adopted to guarantee the reasonability of the recovered models and overall efficiency of the inversion. In addition, this deep-learning (DL)-based framework demonstrates excellent generalization abilities when tested on models that are entirely distinct from the training data sets. The framework can easily incorporate multiphysics without necessitating any structural changes to the network. Synthetic experiments validate that our DL-based method outperforms conventional separate inversions and cross-gradient-based joint inversion in view of the accuracy of the recovered models and inversion efficiency. Successful application to field data further verifies the effectiveness of our DL-based method.

Analysis and Interpretation of Gravity data to modelling ‘PB’ Geothermal Field

The ‘PB’ field is located on the island of Sumatra which is related to the volcanic activity of Kaba hill which still retains residual heat from the magma. One of the geophysical methods used in this case is the gravity method where this method can be applied to determine the location of reservoirs, possible locations for reservoirs, and even to examine geological features and heat sources. In this paper, gravity data is used to interpret the structure and possibility of modelling the heat source in the ‘PB’ geothermal field. The gravity data was analyzed using integrated gradient interpretation techniques such as Horizontal Gradient (HG) and Euler Deconvolution (ED) methods. The CBA map produced shows two dominants high Bouguer anomalies underlying the ‘PB’ geothermal field associated with the presence of dacite and andesitic rocks. Analysis of fault structure based on geological data, HG and ED enhancement data on gravity anomalies was used as a reference for the initial model of subsurface conditions in the inversion model. The 2-D modelling results reflected high-density rocks associated with active ‘PB’ mountain volcanism. The conclusion obtained from the analysis and interpretation of the ‘PB’ geothermal system is that this area still has active volcanism, which is a heat source, with the presence of diatreme found through 2D gravity inversion modeling. The conceptual model results obtained by combining the integration of each reference and existing research show that the upflow zone is at the top of Kaba Hill and the outflow zone is at Babakan Bogor hot spring and Suban hot spring. Thus, these results can provide comprehensive information in analyzing and interpreting as well as the use of enhancement data gravity HG, ED and 2D slice inversion in the description of structures and modelling in the Geothermal ‘PB’ field.