Water-bearing Layer Research Articles

Subduction Style at Different Stages of Geological History of the Earth: Results of Numerical Petrological-Thermomechanical 2D Modeling

In this article we examine the effects of impact of slab rocks eclogitization on the subduction regime under the continent. Eclogitization of rocks in high-pressure metamorphic complexes occurs only in the areas of penetration of hydrous fluid. In the absence of hydrous fluid, the kinetic delay of eclogitization preserves low-density rocks under P‒T conditions of eclogite metamorphism, delaying the weighting of a slab and reducing the efficiency of the slab-pull mechanism which contributes to the steep subduction into the deep mantle. The results of numerical petrological-thermomechanical 2D modeling of subduction under the continent in a wide range of eclogitization parameters of oceanic crust rocks (discrete eclogitization) are presented. The effects of a lower kinetic delay of eclogitization in the water-bearing basalt layer, compared to the drier underlying gabbro layer, have been tested. Based on results of 112 numerical experiments with 7 variants of eclogitization ranges (in range 400–650°C for basalt and 400–1000°C for gabbro) at different potential mantle temperatures (ΔT = 0–250°C, above modern value), and steep, flat and transitional subduction regimes were identified. The mode of steep subduction occurs under modern conditions (ΔT = 0°C) with all ranges of eclogitization. Here it is characterised by an increase in the angle of subduction of the slab as the plate descends, and above the boundary of the mantle transition zone there is a flattening or and then tucking of the slab. Subduction is accompanied by the formation of felsic and mafic volcanics and their plutonic analogues. At elevated temperatures of the mantle (ΔT≥150°С) and discrete eclogitization over a wide range, the flat subduction regime is observed with periodic detachments of its steeper frontal eclogitized part. The flat subduction regime is accompanied by significant serpentinization of the mantle wedge and episodic, scarce magmatism (from mafic to felsic), which occurs at a significant distance (≥500 km) from the trench. During the transition regime, which is also realised in models with elevated mantle temperatures, there is a characteristic change occurs from flat to steep subduction, resulting in a stepped shape of the slab. As the kinetic shift of eclogitisation increases, flat subduction develops. An increase in the thickness of the continental lithosphere from 80 km to 150 km contributes to the implementation of steep subduction, while the influence of the convergence rate (5–10 cm/year) is ambiguous. Discrete eclogitization of thickened oceanic crust and depletion of lithospheric mantle in the oceanic plate are the main drivers of flat subduction. In modern conditions, their influence becomes insignificant due to the decrease in the thickness of the oceanic crust and the degree of depletion of the oceanic mantle lithosphere. As a result, the less frequent flat movement of slabs is determined by other factors.

Delineation and validation of GIS-based groundwater potential zones under arid to semi-arid environment using multi-influence-factors approach

ABSTRACT Groundwater is an indispensable source for domestic-use, agriculture, industry and sustainable development. Groundwater scarcity is Pakistan’s emerging issue, especially in the arid and semi-arid regions of southern Khyber Pakhtunkhwa. This study intends to demarcate the groundwater potential zones (GWPZ) in these regions using Multi-Influence-Factors (MIF), validated with Vertical Electrical Sounding (VES) and well data. The study region was classified into four GWPZ: very high (340 km2), high (4997.11 km2), moderate (17615.14 km2) and poor (16355.46 km2). These interpretations were supported by the VES survey, and water bearing layers have been recognized at 32 m, 137 m, 87 m, 10 m at VES points 1, 2, 3, and 4, respectively in Karak, and at 152 m, 194 m, and 93 m at VES points 1, 2, and 3, respectively in Lakki Marwat, while at 125 m, 119 m and 80 m at VES points 1, 2 and 3, respectively in D. I. Khan. The southern region is predominantly poor, the northern and northeastern parts are high to very high, while the southwest part has moderate potential. Water depth is <40 m at very high potential, 40 to 70 meters at high potential, and 150 to 180 meters in poor zones. This study will help to enhance the applicability of integrated methodologies for groundwater investigations under arid conditions.

Pore-scale investigation of injectivity impairment caused by oil droplets during produced water reinjection using volume of fluid method

Produced water from subsurface may often contain oil droplets, even when not directly extracted from oil wells. Oil droplets can migrate into water-bearing stratigraphic layers, leading to the generation of oily water. This study evaluates the dynamic clogging behavior of oil droplets concerning various injection fluid properties, including injection velocity, interfacial tension, oil droplet size, concentration, viscosity, and medium wettability. The primary objective is to validate common clogging mechanisms associated with oil droplets and quantitatively assess the impact of these parameters on injectivity impairment within porous media. To achieve this, a volume of fluid approach is employed, integrating fluid interfacial properties to account for coalescence and surface adherence. The results are then compared to similar findings in existing literature. Our study reveals that increasing the capillary number enhances injectivity, up to a critical point where the flow regime attains optimal stability, contingent upon relative permeability and phase mobility. Investigation into system wettability demonstrates that while contact angle significantly affects the injectivity index, the impact on injectivity diminishes when altering it beyond 90°. Aligning droplet viscosity with that of the displacing fluid proves to be an effective solution for minimizing injectivity impairment, nearly eliminating damage. This research provides valuable insights into commonly studied emulsion parameters, like Jamin Ratio and oil concentration, and underlines the importance of investigating less-explored factors, such as wettability and oil viscosity, particularly in scenarios involving unstabilized droplets and coalescence dynamics.

Solid waste slurry grouting transformation mechanism of loose sand layer based on slurry-water replacement effect

During coal mining, when loose water-bearing sand layers are exposed and connected, it is extremely easy to cause water and sand inrush accidents, threatening the lives and properties in mines. Because of the intricate and tortuous internal structure of the sand layer, the diffusion pattern of grouting slurry within the loose sand layer has not been accurately characterized. Improving the efficiency of grouting and reducing the cost of grouting are common difficulties faced by industrial and mining enterprises in the grouting renovation of loose water-bearing sand layers. This paper innovatively proposes the mechanism of slurry-water displacement effect based on the diffusion characteristics of grouting slurry within the water-bearing sand layer. It studies the power-law fluid seepage and diffusion mechanism of porous media tortuosity effect and slurry-water displacement effect and derives the spherical diffusion equation of power-law fluid seepage grouting considering the coupling of porous media tortuosity effect and slurry-water displacement effect. At the same time, an indoor experimental device considering the slurry-water displacement effect is designed to verify the rationality of the spherical seepage grouting diffusion equation considering the superimposed effects of the two. Furthermore, relying on the COMSOL Multiphysics platform, a three-dimensional numerical calculation model of the power-law fluid spherical seepage grouting mechanism considering the porous media tortuosity effect and slurry-water displacement effect is constructed. It analyzes the seepage and diffusion characteristics of power-law grouting slurry in water-bearing sand layers, and studies the influence of different porosity of loose water-bearing sand layers, spacing between slurry and water holes, grouting pressure, and slurry viscosity on the volume of loose water-bearing sand layers. The key factors affecting the volume of loose water-bearing sand layers are grouting pressure &amp;gt; spacing between slurry and water holes &amp;gt; porosity of sand layer &amp;gt; slurry viscosity. Compared with previous grouting technologies and processes, the slurry-water displacement grouting technology can solve the problems of small grouting diffusion range and poor grouting effect in high-pressure underwater water-bearing sand layers to a certain extent.

Multi-criteria assessment of groundwater potential of shallow aquifers in the vicinity of Osun state university, Ikire campus and environs, southwestern Nigeria

In order to investigate the groundwater potentials of shallow water-bearing layers within the vicinity of the Osun State University Campus at Ikire, fifteen vertical electrical sounding (VES) resistivity data were acquired at random. The groundwater potential of the shallow water-bearing layers was inferred from the resistivity data based on three (3) existing criteria namely aquifer resistivity, transmissivity and reflective coefficient. At each VES station, the maximum electrode spreading employed for the resistivity data acquisition was between 200 m and 240 m, with the interpretation of the data carried out using partial curve-matching and computer iterative software. Geoelectric parameters obtained were used to compute the longitudinal conductance, transverse resistance, hydraulic conductivity, transmissivity and reflective coefficient using empirical relationships. The computed parameters were compared with existing classification tables to deduce the groundwater propensity in the shallow water-bearing layers of the study area. Four to five geoelectric layers corresponding to the HQ, HA and HKA geoelectric curve types were observed having lateritic materials as topsoil, sandy clay/clayey sand, weathered/fractured basement and fresh basement. In most cases, the water-bearing layer is mostly of clayey material with high porosity and low permeability and resistivity values that varies from 14.6 Ωm in VES 1 to 65.6 Ωm in VES 6. A few consist of sandy clay also with low resistivity values 76.9 Ωm in VES 7 to 107.1 Ωm in VES 4. The transmitivity values vary from 0.239 m2/day in VES 2 to 2.522 m2/day in VES 5. This same behavior was observed with reflective coefficient values which range from 0.690 in VES 6 to 0.994 in VES 1. The conclusions from the classification tables correlate in most of the VES stations. This study shows that the groundwater potential of the shallow water-bearing layers in the study area is generally poor within 0 to 80 m depth due to the low transmissivity of the clay materials at the shallow depths. Effective groundwater development in the study area must therefore integrate geophysical methods and remote sensing techniques to investigate depths beyond 100 m.

Spatial infiltration and redistribution of light crude oil in heterogeneous water-bearing soil layers under different hydrogeological processes.

Two physical models were used to simulate the infiltration and redistribution process of light crude oil after leakage in a heterogeneous soil layer following water level variation and rainfall. Migration fronts and redistribution characteristics of oil during gravity seepage, water level variation, and rainfall were obtained using charge-coupled device (CCD) camera shooting and cyan-magenta-yellow‒black (CMYK)-based gray analysis, which were employed efficiently and at a low cost. Then, the influencing factors and migration mechanisms were examined. Finally, the soil water and oil contents were measured to verify the simulation results. The results are as follows: (1) the geologic lens and fine-coarse interface can intercept oil, resulting in a local highly contaminated area. (2) The crude oil infiltration path and velocity varied greatly with the different soil types and initial water contents. Within a certain range, the higher the initial water content is, the higher the lateral and vertical infiltration speeds. (3) The oil redistribution process was dominated by vertical infiltration under the condition of water level variation or rainfall, but oil-water displacement and the capillary pressure caused some oil to move horizontally near the geologic lens and fine-coarse interface. (4) Water level variation resulted in a synchronous rise or fall of the oil accumulation area, but rainfall caused it to move up. (5) Water level variation and rainfall imposed a certain influence on the periodic accumulation and release of crude oil in heterogeneous soil, especially in the presence of geologic lenses and lithologic interfaces.

Geospatial and geophysical insights for groundwater potential zones mapping and aquifer evaluation at Wadi Abu Marzouk in El-Nagila, Egypt

This study employs an integration of remote sensing, geographic information systems (GIS), and geophysical techniques to delineate groundwater potential zones (GWPZ). This multidisciplinary approach significantly enhances the precision and reliability of groundwater potential zone mapping. Eight criteria were introduced into the analytic hierarchy process (AHP) to identify GWPZs in Wadi Abu Marzouk by applying a weighted overlay analysis of all criteria layers. The criteria weights were derived by using a pairwise-comparison technique, while the accuracy of the weightage process was calculated by the consistency ratio as 0.06. As revealed in the GWPZ analysis, the northern and northwestern regions have the highest groundwater potentiality. Thirty-five vertical electrical soundings (VES) and four electrical resistivity tomography (ERT) profiles were measured across the study area. The interpretation of geophysical data revealed the presence of a water-bearing layer at depths varying between 27 and 51 m from the ground surface. Its resistivity values indicate the existence of freshwater in the northern and northwestern parts, which highly matches the GWPZ analysis results. However, the southern parts of the area are dominated by saltwater. The integration between geospatial techniques, geophysics, and hydrogeology forms a robust scientific approach, with invaluable insights for sustainable water resource management.

Estimating Thermal Impact on Groundwater Systems from Heat Pump Technologies: A Simplified Method for High Flow Rates

This research delves into the potential thermal effects on underground water systems caused by the use of thermal technologies involving extraction and injection wells. We developed a unique approach that combines straightforward calculations with computer-based modeling to evaluate thermal impacts when water flow rates exceed 2 L/s. Our model, based on a system with two wells and a steady water flow, was used to pinpoint the area around the thermal technology where the temperature varied by more than 1 °C. Our findings suggest that the data-based relationships we derived from our model calculations provide a cautious estimate of the size of the affected area, or ‘thermal cloud’. However, it is important to note that our model’s assumptions might not fully account for the complex variables present in real-world underground water systems. This highlights a need for more research and testing. A key contribution of our study is the development of a new method to assess the thermal impact of operations involving heat pumps. In conclusion, while our proposed method needs more fine-tuning, it shows promise in estimating temperature changes within water-bearing rock layers, or aquifers. This is crucial in the effective use of thermal technologies while also ensuring the protection and sustainable management of our underground water resources.

Groundwater Hydrochemistry and Aquifer Identification at Wana Area, Northwest of Mosul, Iraq

The suitability of groundwater for various uses is primarily determined by its major ions content, which is determined by its hydrochemical properties, including geogenic and anthropogenic factors. To gain a deeper understanding of groundwater management and sustainability in Wana, one of the most important agricultural areas northwest of Mosul, 18 wells were chosen and groundwater samples were taken from them over two seasons (October 2020 and April 2021) and their physicochemical properties were analyzed. The Piper diagram revealed that the most common type of groundwater in the study area is Ca-SO4. The mineral saturation index, cation exchange values, and Gibbs diagram results revealed that rock dissolution and weathering processes, including both gypsum and carbonate rocks, dominated the chemistry of groundwater in the region, with clastic rocks and ion exchange processes having a limited effect. This is also confirmed by the findings of the Principal Component Analysis, which further revealed that there is an effect of an anthropogenic factor caused by agricultural activities on the concentration of NO3-. The Cluster Analysis results revealed three groups of wells based on the water-bearing layers: those that draw water from the Quaternary deposits aquifer, those that draw water from the Fatha Formation aquifer, and those that draw water from both aquifers. The findings of this study can contribute to the preservation and sustainability of groundwater, as well as the optimal management of this crucial resource in the studied region.

Application of the Electromagnetic Method to the Spatial Distribution of Subsurface Saline and Fresh Water in the Coastal Mudflat Area of Jiangsu Province.

Interfacial zones straddling terrestrial and marine realms, colloquially known as mudflats, epitomize a dynamic nexus between these environments and are fundamental to the coastal ecosystem. The investigation of these regions is paramount for facilitating infrastructural developments including ports, wharfs, cross-sea bridges, and the strategic utilization of freshwater resources sequestered from mainland islands amid ongoing economic progress. Terrestrial realms conventionally employ electromagnetic techniques as efficacious modalities to delineate subterranean geological information, encompassing structural details and water-bearing strata. However, the peculiar topographic and geological nuances of mudflat regions pose substantial challenges for the efficacious application of electromagnetic methodologies. The present paper endeavors to address these challenges by suggesting innovative modifications to the existing instrumentation and evolving novel data acquisition techniques specifically tailored for electromagnetic exploration within mudflat environments. This paper delves into the electrical characteristics of water-bearing layers within mudflats, and ascertains details pertaining to the subterranean structure and the spatial distribution of fresh and saline water resources, through the holistic interpretation of a multitude of profiles.

Coupled analysis of monopile offshore wind turbine under modified three-dimensional seafloor ground motions

The safe operation of offshore wind turbines (OWTs) is significantly influenced by the combined effect of wind, waves, and offshore earthquakes. However, limited seafloor ground motion data have been used to determine the dynamic characteristics and responses of OWTs subjected to offshore earthquakes. Hence, synthetic seafloor ground motions are particularly important for seismic analysis of OWTs. This paper proposes a new method to simulate seafloor ground motions. In the study, the dynamic shear modulus of the water-bearing soil layer and the damping effect of the soil–seawater layers were introduced to modify the simple Crouse and Quilter (C-Q) model in seawater and P-SV and SH transfer function models at offshore sites. Further, three-dimensional seismic waves were synthesized based on the modified transfer function models at a typical offshore site with bedrock–soil–seawater layers, and a fully coupled numerical analysis model of OWTs, including the rotor nacelle assembly, tower structure, and substructure with pile–soil interaction (PSI) under wind, wave, and seafloor ground motion, was established by incorporating the earthquake module and PSI module into the updated FAST v8 software. Moreover, based on the established coupled OWT model, the measured seafloor ground motion records and the seafloor ground motions synthesized using the proposed method were compared, and a coupled analysis of the OWT under wind, wave, and offshore earthquake loadings was carried out. Furthermore, the coupled mechanisms of the OWT under synthesized and recorded seafloor ground motions were determined.

A Study of Groundwater Aquifers in Tumbur Village Wer Tamrian District Tanimbar Islands District

Water is a primary human need that must be met, but as time increases, the rate of population growth means that water needs are increasingly not being met. The geoelectric method is a geophysical method that utilizes electrical properties to interpret the earth's subsurface. The main aim of the geoelectric method is to find the resistivity value of a rock. The higher the resistivity value, the more difficult it is for the rock to carry an electric current, and vice versa. For this reason, one solution to meet the needs of the Lorulun Village community is to search for groundwater aquifers using one of the methods that can be used, the geoelectric resistivity method. The data collection and analysis method used in this research is to conduct a survey at the location to review and see the conditions directly at the research location. Identification To determine the existence of a water-bearing layer at a certain depth, we can use geophysical methods, namely the geoelectric resistivity method, to obtain an overview of the soil layers below the surface. Apart from that, it can also predict the potential for deep and shallow groundwater in the research area. The problem in this research is analyzing deep groundwater sources based on the characteristics and implementation of geoelectric results and the aim of this research is to conduct a survey and design deep groundwater wells based on the characteristics and implementation of geoelectric results in Tumbur Village, Wer Tamrian District. The data is processed based on the apparent resistivity equation, so that the apparent resistivity value (ρa) is obtained by entering the values ∆V, I, a, and K into the Microsoft Excel program. Then processed using RES2DINV software. The water source is at two points, namely geoelectric drilling points 01 and 02, respectively, where the aquifer is found. The casing screen installation process is placed at 3 meters and 12 meters. The use of gravel packs from a depth of 2 to 12.5 meters is to protect the drilled wall hole from landslides and also act as a filter for mud or other materials entering the screen. and with a depth of ± 15 meters, the resistivity shows a brackish water aquifer. This is caused by the influence of seawater intrusion By conducting a survey and designing a deep-ground water well based on the characteristics and implementation of geoelectric results in Tumbur Village, Wer Tamrian District,

A method for assessing the effectiveness of water isolation works based on the development of a hydrodynamic model

An important task at the stage of designing any activity related to oil recovery enhancement (in the present case repair and isolation works), is process modeling, in particular, hydrodynamic modeling. Modeling is used to forecast the parameters of oil recovery as s function of the implemented technology at the design stage. As a result, the cost of works performed can be reduced and the profitability and success rate of the planned activities can be assessed. The paper considers the assessment of technological and economic effects using the developed two-phase hydrodynamic model simulating oil-saturated and water-bearing layers. Discussed are the calculated values and relationship between skin factor and various isolation factors. The graphs of oil flow rate and water cut as functions of the material isolation factor are given. Keywords: water isolation; hydrodynamic model; skin factor; isolation factor; water inflow.

Groundwater quality assessment along the West of New Damietta Coastal City of Egypt using an integrated geophysical and hydrochemical approaches

Recently, the groundwater became very important source for the Egyptian water balance. Therefore, assessing its quality and quantity is necessary before initiating any developmental plans using this resource. In this research, a new operated power plant, which is located in the coastal area of West New Damietta City, north-east of Egypt was designed to work using the coastal groundwater aquifer. Therefore, an integrated approaches of both geophysical methods and hydrochemical analysis were applied to identify the subsurface lithology, the water-bearing layers and determine the potential use of such coastal groundwater. Therefore, a total of seventeen vertical electrical soundings (VES) and five time-domain electromagnetic soundings (TEM) were performed. Moreover, groundwater samples were collected from seven existing wells to be analyzed for water quality assessment. The geophysical results identified five geoelectric layers. The first geoelectric layer has a resistivity of 1–7.9 Ω m and a thickness range of 7–9 m. The second layer has a resistivity of 0.9–4.4 Ω m and a thickness range of 7–8 m. The third layer is 10–21 m thick with a resistivity value of 0.5–2 Ω m. The fourth layer, which is thicker (29 to 42 m), has a resistivity of 0.7–3 Ω m, while the last layer has a resistivity of 1.7–9 Ω m. According to the hydrochemical analysis, the aquifer is dominated by Na–Cl water type. The brackish nature of the water is revealed by the TDS range of 7035 mg/l to 7735 mg/l. The results collected demonstrate the groundwater's quantity and quality availability for the power plant’s sustainable use.

Modelling 2050 Water Retention Scenarios for Irrigated and Non-Irrigated Crops for Adaptation to Climate Change Using the SWAT Model: The Case of the Bystra Catchment, Poland

The paper presents the estimated changes in the soil water content, the total runoff, the sediment yield and the actual evapotranspiration for the small Bystra catchment in the east of Poland. The findings are based on the results of three simulations covering the years of 2041–2050. The simulations were based on a calibrated and validated SWAT model (2010–2017). The first variant covers just the climate change and the existing structure of soil cultivation for the three regional climate models supported by the EC-EARTH global climate model in the emission scenarios RCP4.5 and RCP8.5. Variants two and three are based on the first variant in terms of the changing climate. The second variant, however, involves placing a pond in each farm in the catchment, while the third variant involves designing huge reservoirs as a result of land consolidation. Variants two and three occur in five adaptation scenarios each. The first adaptation scenario (V2.1 and V3.1) involves only increasing the number of ponds on the farm or increasing the number of reservoirs for non-irrigated arable land crops, i.e., WWHT (winter cereals), BARL (spring cereals), CANP (rapeseed) and CRDY (other crops). The second adaptation scenario (V2.2 and V3.2) involves growing vegetables without irrigation (instead of cereals). The third adaptation scenario (V2.3 and V3.3) involves growing vegetables with irrigation (instead of cereals). The fourth adaptation scenario (V2.4 and V3.4) involves partial cultivation of vegetables and cereals. The fifth adaptation scenario (V2.5 and V3.5) involves partial cultivation of orchards and cereals. The adaptation scenarios of the irrigation of vegetables from deep water-bearing layers (second variant) or reservoirs (third variant) contribute to the increase in water content in the soil, especially in summer, in comparison with the adaptation scenarios for vegetable cultivation without irrigation. What is more, the actual evapotranspiration was higher in the adaptation scenarios involving irrigation than in scenarios without irrigation. It is known that the changes in water content in soil and the intensification of water erosion are gravely affected by modifications in crops and soil cultivation. A change from cereal cultivation to irrigated vegetable cultivation or orchards increased the water content in the soil in most climatic projections. However, the increase in the number of ponds in the second variant had little impact on the soil water content, actual evapotranspiration and overall runoff, while the erosion loss decreased. With the lower precipitation levels in the years 2041–2050 relative to 2010–2017, as presented in the emissive scenario RCP 4.5, the soil water content decreases by up to 14% for most variants. Total runoff for most variants will also be lower by 4–35%. The percentage change in sediment yield will fluctuate between −86% and 116%. On the other hand, the actual evapotranspiration for most variants will be higher. With higher precipitation levels in the years 2041–2050 relative to 2010–2017, as presented in the emissive scenario RCP 8.5, the soil water content changes slightly from −7% to +3%. Total runoff for most variants will also be higher by as much as 43%. Sediment yield for most scenarios may increase by 226%. The actual evapotranspiration for most variants will also be higher. Irrigation variants tend to increase soil available water while increasing evapotranspiration and total outflow in the catchment as compared to non-irrigated LULC. The largest increase in the soil water content is observed in most irrigation variants for RCP 4.5 (annual average 316–319 mm) (V2.3-V2.5, V3.2, and V3.3) and RCP 8.5 (annual average 326–327 mm) (V2.3-V2.5 and V3.3) as compared to V1 (BaU) (315 mm–RCP 4.5 and 324 mm–RCP 8.5) for the years 2041–2050. On the other hand, the lowest increase in soil water content is observed in the V3.5 variant, with an annual average of 292 mm for RCP 4.5 and an annual average of 311 mm for RCP 8.5. Thus, for future climate change scenarios, irrigation with water reservoirs (ponds and storage reservoirs) should be considered. The study proves the rationale behind building ponds in small catchments in order to increase water resources in a landscape and also to counteract adverse effects of climate changes, i.e., sediment outflow and surface water erosion.

Groundwater Investigation Using Electrical Resistivity Method at New Borg El-Arab City, Alexandria, Egypt

New Borg El-Arab is a city located on the northwestern coast of Egypt, where the increasing anthropogenic activities have led to an increase in water demand. Groundwater is the main source of water in this area, but it is seriously affected by the Mediterranean saltwater intrusion. This causes a substantial impact on the water quality of the coastal aquifer. In this study, the electrical resistivity method was applied to delineate the shallow groundwater aquifer and its quality. Twenty vertical electrical soundings (VES) distributed along 6 profiles were measured. To observe the seasonal groundwater variations, 14 VES points were measured at the end of the rainy season, while the measurements of 6 VES points were repeated at the end of the dry season. The results revealed 4 geoelectrical layers; the first layer is a surface dry zone with variable resistivity values, followed by a water-bearing layer; while the third is a limestone layer, followed by a clay deposits zone. In comparison to the winter season, the water-bearing layer records lower resistivity values at the end of summer. Optimal locations to drill new groundwater wells have also been determined with a depth varying from 1.8 m north to about 30 m south.

Numerical Simulation and Sensitivity Analysis of Hydraulic Fracturing in Multilayered Thin Tight Sandstone Gas Reservoir

Hydraulic fracturing is a necessary measurement to realize the commercial exploitation of oil and gas, but its application in multilayered thin tight sandstone gas reservoirs is still not perfect, which usually have thin gas layers mixed with complex intervals, and shows a dramatic variation in geological and geomechanical properties in the vertical direction. When conventional hydraulic fracturing methods are applied to this kind of reservoir, it is hard to get proper fracture propagation, especially for fracture height control. Facing this situation, this paper proposes a numerical study of the hydraulic fracturing mechanism and analyzes its influencing factors in the multilayered thin tight sandstone gas reservoir. Relying on a real reservoir in the Ordos Basin in China, relevant geological and geomechanical parameters of major gas layers and interlayers are obtained. According to these parameters, the hydraulic fracturing simulation in the multilayered thin tight gas reservoir model is carried out, based on which, the sensitivity analysis of different geological and fracturing parameters which affect the fracture propagation is performed. Furthermore, a real low-production well after fracturing in this kind of reservoir is selected as an example, and based on the analysis, an optimized fracturing scheme is proposed to adapt to the characteristics of the reservoir. According to the comparison of fracturing and production simulations, the optimized fracturing scheme can prevent hydraulic fractures from breaking through thin interlayers, control the fracture height, and prevent fractures from communicating strata with a high water-bearing layer. At the same time, with the same amount of proppant and fracturing fluid, longer fracture length and better fracture conductivity are created, so that the productivity of the optimized fracture has been greatly improved.

2D and 3D visualization of aquifer sediments, surface water seepage and groundwater flow using DC-resistivity, DC-IP, and SP methods, West El-Minia, Egypt

In this study, the SP, DC-Resistivity and DC-TDIP methods were used and included 21 sites for determining the groundwater conditions and visualizing the aquifer sediments, surface water seepage, and groundwater flow in 2D and 3D. The results indicated the occurrence of Quaternary and Tertiary deposits, as well as shallow aquifer of Eocene fractured limestone and Quaternary deposits. The resistivity, chargeability and SP values were compared with each other and 2D and 3D visualization models were designed for these values to understand the sediment distribution and its geological and hydrogeological implications. High to medium, low and very low chargeability values indicated the compact sediments with high shale content, water-bearing layers and freshwater zones and dry sediments, respectively, and varied with the water amount, salinity and effective porosity. Low to very low values of SP indicated the occurrence and high accumulation of groundwater and an increase in shale, permeability and groundwater flow and source, and possibly salinity. The results showed that the resistivity, chargeability and SP values had an important role in separating the dry and saturated sediments and defining the fault zone, determining the source of surface water seepage, classifying the depths of high, medium and low groundwater accumulation and flow and permeability. The IP depended highly on the water amount and shale content and it was interesting in groundwater exploration with resistivity and in differentiating between groundwater and clays. The SP assisted in delineating the surface water seepage and groundwater source and flow direction, and predicting the sediments permeability.

Dynamics of Pollution in the Hyporheic Zone during Industrial Processing Brine Discharge

The industrial production of chemicals, including the manufacture of mineral fertilizers, is often associated with the need for the disposal of highly mineralized brines through their discharge into surface water bodies or an underground water-bearing layer. When dealing with surface water bodies, the problem of the hyporheic zone effect could substantially influence the process and, thus, must be examined. We consider a two-layer system (liquid–porous medium) for a detailed assessment of the importance of considering the hyporheic zone during the modeling of brine discharge. A three-dimensional numerical simulation of brine transport is performed for parameters close to the characteristics of the media and flows typical for natural water bodies. The dynamics of a saturated brine in a two-layer system are studied for the period of brine discharging and after the cessation of the disposal, and the accumulation of salts in the bottom porous layer is assessed. Calculations show that a significant amount of impurities is observed not only near the water body bottom but also throughout the entire thickness of the porous layer. Moreover, the obtained data reveal that the effect of vertical stratification dramatically influences the brine discharge process and leads to propagation of the brine into the porous medium with a velocity that is three orders of magnitude higher than the filtration rate in the horizontal direction. As a result, the heterogeneity in the depth distribution of the impurity concentration is significant. In particular, the maximum concentration of salt in the hyporheic zone exceeds those near the river surface by hundreds of times. Impurities accumulated in the water-bearing layer of the river bottom are nonhazardous at low- and medium-flow rates. However, with an increase in the river flow intensity—for example, during the flood period or caused by operating regime of a hydroelectric power plant—the accumulated contamination may become an intensive source of pollution, which significantly limits the water use regime.

ОЦІНКА СТІЙКОСТІ ДІЛЯНКИ СХИЛУ ОДЕСЬКОГО УЗБЕРЕЖЖЯ

Currently, there is a reduction in sites convenient for the construction of facilities. In this regard, the question of the development of new territories that were previously considered unsuitable or economically unprofitable for construction is increasingly being raised. Very often it is necessary to build buildings and structures on or near slopes. The development of landslide and landslide-prone slopes requires a comprehensive study, the results of which should be used in the selection of measures for the engineering protection of territories, as well as design and construction on slopes. The main task of engineers, when performing design and survey work in landslide-prone areas, is to assess the stability of the slope and the magnitude of the landslide pressure. The article calculates the stability of the landslide-prone slope of the Odessa coast for the purpose of further construction development. The slope in question is located on the Franzysky Boulevard, in the area of the Chkalov resort. The site features are in complex engineering and geological conditions (loess soils, collapsing properties of soils, several water-bearing layers). It has been established that deep block landslides of extrusion occurred earlier in this area. After landslide control measures consisting in construction of marine cost protection and drainage structures, an increase in slope stability was observed. Despite the measures taken, there is a beach erosion with partial destruction of coast protection structures, which can lead to increased abrasion and negatively affect the stability of the entire slope. Slope stability calculations are performed in two-dimensional and three-dimensional formulation. According to the flat schemes, calculations were performed in the Slide software package using Bishop and Janbu methods. The slope stability assessment in a three-dimensional formulation was performed by the finite element method using the Midas GTS NX calculation program and consists of determining the stress-strain state of the soil mass and the stability margin factor. Based on the calculation results obtained, the slope stability is assessed and options for landslide control (retaining) structures are proposed.