Complex Hydrogeology Research Articles

Experience of using the Aptian-Albian-Cenomanian hydrogeological complex in the disposal of produced water from the Kamennoye subsoil area

The objective of the presented study is to assess the efficacy of the Aptian-Albian-Cenomanian hydrogeological complex in the disposal of surplus associated water generated in large quantities during oil production within the Kamennoye subsoil area.The necessity for utilising produced water within the Kamennoye subsoil area is justified by the accumulated volume of water currently exceeding 10 000 thousand m3. The water content in wells' production at the Kamennoye subsoil area is 52-55 %. Furthermore, further extraction will result in an increase in the water cut. One of the key challenges facing subsoil users is to minimise the negative impact of water disposal into the absorbing horizon.In the course of the study, the following tasks were solved: assessment of the natural geological and hydrogeological conditions of the Aptian-Albian-Cenomanian hydrogeological complex, analysis of the stability of the hydrogeochemical indicators of the groundwater in the complex based on the results of monitoring studies (since the 1960s), assessment of the compatibility of the produced water and the formation water by calculating the carbonate equilibrium of the system. The obtained solution of each of the above tasks indicates the rationality of using the Aptian-Albian-Cenomanian hydrogeological complex for the disposal of produced water. The article also emphasises the necessity of continuous improvement of the system for monitoring the condition of the absorbing horizon, as well as careful observance of all environmental protection measures, which is a prerequisite for preserving the natural balance of the subsoil of the West Siberian oil and gas basin.

Нydrogeological characteristics and analysis of the compatibility of disposal and formation water at the field N in Western Siberia

The article presents the hydrogeochemical characteristics of a field located in the West Siberian megabasin in Khanty-Mansiysk Autonomous Okrug — Ugra, the peculiarity of the hydrogeochemical conditions of which is confined to the elysium lithostatic system and inversion hydrogeochemical zonality. This is characterised by a decrease in mineralisation with depth and a change in formation water type. This is related to the transformation of organic and mineral matter in sedimentary rocks at the elision stage of the West Siberian megabasin development during their sinking and compaction. The object of placement of formation and used water is the Aptian-Albian-Cenomanian hydrogeological complex.The article calculates the compatibility of formation waters of the Aptian-Albian-Cenomanian hydrogeological complex and hosted waters, and also estimates the probability of swelling of clay minerals in the reservoirs of this complex.

Groundwater Exploration and Assessment in Arid and Semi-Arid Regions of Basaltic Terrain of Solapur: Lessons Learned and Future Prospects

This research delves into the intricate dynamics of groundwater exploration and assessment in the arid and semi-arid basaltic terrain of Solapur, India. The study investigates the hydrogeological complexities of the region, emphasizing the importance of community involvement and sustainable practices in groundwater management. Employing advanced geophysical surveys, borehole logging, and hydrogeological modeling, the research uncovers the challenges and successes encountered during the study, providing valuable insights for future exploration strategies. Key findings highlight the heterogeneity of basaltic formations, the significance of local community engagement, and the need for adaptive approaches in groundwater exploration. Lessons learned from successes in geophysical surveys and challenges faced in borehole logging contribute to the knowledge base for effective exploration techniques in similar geological settings. The research's significance for Solapur lies in its potential to guide sustainable water management practices, empower local communities, and inform policy formulation. The emphasis on community involvement, awareness, and regulatory measures serves as a foundation for addressing water scarcity challenges in the region. Beyond Solapur, the study holds broader implications for arid and semi-arid regions globally. It contributes to scientific knowledge, informing policy frameworks, and promoting community-centric approaches to groundwater management. The research provides a blueprint for addressing water resource challenges in diverse geographical contexts, ensuring the resilience of communities and the preservation of vital groundwater resources.

An integrated study of Atopobathynella (Parabathynellidae, Bathynellacea) species reveals restricted distributions in a complex hydrogeological setting: two new species from the Pilbara (Australia)

Abstract The Pilbara bioregion (Western Australia) has become a hotspot for subterranean fauna as a consequence of many surveys conducted to comply with Western Australian environmental regulation requirements. In this bioregion, mining developments can have major implications for subterranean fauna and their conservation. However the diversity and species distributions of most taxa are still poorly known, including the crustacean family Parabathynellidae. Recent studies on a widespread genus of this family (Atopobathynella) from the Pilbara highlighted several undescribed taxa with interesting patterns of distribution. In the Gudai Darri locality, the northern flank of the Hamersley Range occurs as a stepped escarpment intersected by dykes and gullies, with groundwater occurring within fractured rocks abutting the Fortescue River valley, where a separate regional aquifer occurs. This investigation aimed to observe whether stygofauna species distributions (1) reflected the separation between the two major aquifers within the Hamersley Range and the Fortescue Valley; and (2) were influenced by the presence of dykes. We examined the Atopobathynella species occurring in the study area using morphological and molecular data. The results reflected the hydrogeological complexity of the study area with six new lineages of Atopobathynella, recorded mainly in different gullies, that do not share a most recent common ancestor. Two species are described here A. pagetae sp. nov. and A. lythei sp. nov., and four additional species are delineated through preliminary morphological analyses and molecular data. This study will improve future environmental impact assessments and the understanding of Parabathynellidae taxa distribution in hydrogeological complex areas.

Case study on long-term deformation monitoring and numerical simulation of layered rock slopes on both sides of Wudongde dam reservoir area

Layered rock slope exists widely. Because of its special slope structure, it is prone to bending deformation and toppling failure, which is a serious threat to engineering construction and safety operation. At present, the research of layered rock slope still has great innovation potential. During the construction of Wudongde Hydropower Station on Jinsha River, safety and stability problems such as slope geological structure development, face rock unloading and relaxation, and even slip and large deformation were encountered. Through field exploration, it is found that the rock and soil stratification of the slope on both sides of Wudongde Hydropower Station is highly obvious. At present, there is a lack of research on-site long-term displacement monitoring of layered rock high-steep slope, especially for layered slope in complex hydrogeology and construction environment. In order to strengthen the research on the deformation and stability of layered rock slope, this paper analyzes the measured displacement data of Wudongde hydropower station slope, and establishes three-dimensional geological finite element model with the help of numerical simulation software. The stability of the slope is calculated by combining the finite difference method and the strength reduction method. Finally, the evolution mechanism of the deformation of the layered rock slope is explained according to the geological structure characteristics. The main conclusions of this paper are as follows: the layered slope in the dam reservoir area is prone to deformation under the combined action of long-term construction disturbance and fissure water seepage, and the construction disturbance has a strong influence on the artificial excavation area below 1070 m, and the maximum rock mass deformation and surface displacement in the artificial excavation area of the slope reach 92.2 mm and 312.5 mm, respectively. However, the influence of construction disturbance on the natural mountain above 1070 m is limited, the valley deformation of the natural mountain on the left bank of the reservoir area is higher than that on the right bank, and the cumulative deformation is still less than 20 mm. The influence of seepage on the displacement of the area with higher elevation at the top of the slope is more obvious, and the influence of excavation and other disturbances on the displacement of the artificial excavation area with lower elevation is more obvious. The deformation of the river valley in the water cushion pond behind the dam increases slowly, and the change trend of the field deformation data is mostly consistent with that of the numerical calculation. The horizontal shrinkage of the mountains on both sides shows a contraction trend on the whole, and the maximum horizontal shrinkage calculated by numerical simulation is close to 20 mm, which is located at the elevation of 990 m.

Factors аffecting mineralization of groundwater in deep oil and gas bearing horizons in the western part of the West Siberian megabasin

The purpose of this study was to identify the causes of the observed hydrogeochemical situation and the factors contributing to its formation within the Middle Jurassic hydrogeological complex in the western part of the West Siberian megabasin, using the Talinskoye oil field as an example. The research primarily involved constructing dependencies between mineralization (y) and various factors including porosity, reservoir pressure, modern and paleotemperature of the foundation, and depth of the foundation (x). The study evaluated the degree of connection between each parameter and mineralisation. The results showed that the initial hydrochemical state in the area is heterogeneous, with significant variations in mineralisation levels within a single reservoir. The closest dependencies have been revealed between mineralization and porosity of reservoir rocks (an inverse dependence), mineralization and reservoir pressure (a direct dependence). The practical significance of the study is justified by the need to understand the nature of the formation of the hydrogeochemical environment in order to preserve it, control changes, as well as solve issues related to the forecasting, preservation, and destruction of oil deposits.

Multi-tracer approach to constrain groundwater flow and geochemical baseline assessments for CO2 sequestration in deep sedimentary basins

Geological storage of gases will be necessary in the push to net zero and the energy transition to reduce carbon emissions to atmosphere. These include CO2 geological storage in suitable sandstone reservoirs. Understanding groundwater flow, connectivity and hydrogeochemical processes in aquifer and storage systems is vital to prevent risk and protect important water resources, such as the Great Artesian Basin. Here, we provide a ‘tool-box’ of geochemical assessment methods to provide information on flow patterns through the basin's aquifers (changes in chemistry along flow path), stagnant versus flowing conditions (cosmogenic isotopes and noble gases), inter-aquifer connectivity and seal properties (major ions, Sr and stable isotopes), water quality (major ions and metals) and general assessments on residence times of groundwater (cosmogenic isotopes and noble gases). This information can be used with reservoir and groundwater models to inform on possible changes in the above-mentioned processes and serve as input parameters for CO2 injection impact modelling. We demonstrate the use and interpretation on an example of a potential CO2 storage geological sequestration site in the Surat Basin, part of the Great Artesian Basin, and the aquifers that overly the reservoir. The stable water isotopes are depleted compared to average rainfall and most likely indicate greater contributions from monsoonal rain events from the northern monsoonal troughs, where amount and rainout effects lead to the depletion rather than colder recharge climates. This is supported by the modern recharge temperatures from noble gases. Inter-aquifer mixing between the Precipice Sandstone reservoir and the Hutton Sandstone aquifer seems unlikely as the Sr isotope ratios are distinctly different suggesting that the Evergreen Formation is a seal in the locations sampled. Mixing, however, occurs on the edges of the basin, especially in the south-east and east where the Surat Basin transitions into the Clarence-Moreton Basin. Groundwater flow appears to be to the south in the Precipice Sandstone, with a component of flow east to the Clarence-Morton Basin. The cosmogenic isotopes and noble gases strongly indicate very long residence times of groundwater in the central south Precipice Sandstone around a proposed storage site. 14C values below analytical uncertainty, R36Cl ratios at secular equilibrium as well as high He concentrations and high 40Ar/36Ar ratios support the argument that groundwater flow in this area is extremely slow or groundwater is stagnant. The results of this study reflect the geological and hydrogeological complexities of sedimentary basins and that baseline studies, such as this one, are paramount for management strategies.

Investigating the enigma of an irregular groundwater age pattern in a confined, presumed “fossil” complex aquifer through mixing cell flow modeling

Significant fluctuations in the groundwater (GW) age along the eastern flow path of the Nubian Sandstone Aquifer's (NSA), as derived from Krypton-81 groundwater dating, have suggested that this aquifer, located in Israel's Negev Desert and previously presumed to be a fossil, is not entirely isolated but mixes with younger and even recent water. The intermittent rejuvenation and drastic increases in the GW age across short distances most likely imply hydraulic connectivity with the surrounding aquifers, which contribute both younger and more ancient water to the NSA. The current study aims at modeling the GW flow system to locate and quantify its water sources despite the aquifer's hydrogeological complexity and the scarcity of hydrological data. We implemented the Mixing Cell Modeling (MCM) approach, understanding that the alternating rejuvenations and increases in the GW age downstream of the NSA's eastern flow trajectory reflect the mixing of the NSA's groundwater with young and old GW bodies, respectively. Thus, prompted by the 81Kr water age distribution, yet independent of the Kr radioisotope data, a multi-tracer mixing cell flow model was adopted based on a set of balance equations of water, dissolved minerals, and stable environmental isotopes. The findings indicate that (1) there is a small, yet substantial, intrusion of old brackish GW from a deep-seated, highly pressurized aquifer into the NSA in the northeastern Negev; (2) the rejuvenation of GW in the NSA is due to significant mixing with water from nearby overlying carbonate and chert aquifers, and (3) the NSA is substantially replenished through the Nubian Sandstone (NS) outcrops along the Negev Desert anticlines. Most GW intrusions into the NSA occur near the intersections of the eastern flow path with some of the Negev's major faults and synclines, such as the Paran and Ramon Fault zones and the Zin Syncline. In light of the relatively young GW age at the end of the NSA's western flow path in the northern Negev, and based on the similarities in the hydrogeological structures in the Negev and northern Sinai Deserts, we propose that similar mixing processes with GW from the overlying carbonate aquifers and direct GW recharge through the NS outcrops also occur in the northern Sinai Peninsula. The approach presented in this study might apply to examining recharge processes and hydraulic connectivity in other aquifers that were formerly classified as “fossil,” such as the immense NSA found in the Arabian (Jordan & Saudi Arabia) and the Western (Egypt) Deserts.

GEOMORPHOLOGICAL, HYDROGEOLOGICAL AND GROUNDWATER QUALITY ANALYSIS IN KARST SYSTEMS OF THE CENTRAL-WESTERN PART OF METALIFERI MOUNTAINS

This scientific study focuses on the relatively lesser-known karst areas in the central-western part of Metaliferi Mountains. These surfaces display pronounced spatial fragmentation, forming limestone klippes with well-defined karst systems of geomorphic and hydrogeological complexity. Using GIS and statistical methods, the study highlights the morphological and distributional traits of the identified karst forms. Additionally, the area was analysed from a hydrogeological standpoint to explore the connections between the identified insurgences and exsurgences, and the impact of the karst environment on the chemical characteristics of karst waters. The geomorphological analysis reveals a clustered and non-uniform arrangement of depression forms, as shown by the nearest neighbour index, with a quasi-circular shape highlighted by the Circularity Index. From a hydrogeological perspective, there is an increase in carbonate ions (HCO3-) and calcium ions (Ca2+), along with a decrease in Fe and Al ions, indicating possible alluvium presence as a filter. The comparison of these values with legal thresholds demonstrates a high water quality in the analysed karst exurgences.

PREDICTIVE NUMERICAL GEOFILTRATION MODEL OF GROUNDWATER INFLOW INTO THE GOREVSKY GOK QUARRY

Gorevskoe zinc-lead ore deposit is located within a unique terrain: it follows the left bank of the Angara River and lies underneath its current river bed, starting 38 km far from the Angara River mouth. This plays a significant role in the ore field hydrogeology and has a great impact on its further development. The complexity of ore field hydrogeology is defined by a number of natural factors, i.e., the occurrence of both aquifers as well as low-permeable and water-proof layers; tectonic failures (if any) and their functioning in terms of hydrogeology dynamics; variability in terms of water-bearing rocks hydraulic properties; water bodies on the surface and their connection with groundwater flows. All the above mentioned features allow us to classify Gorevskoe deposit hydrogeology as rather complex and complicated. The main task of the work performed was to evaluate and forecast the water inflow to Gorevskii open-pit mine and to determine the groundwater level at the end of mining operations. Because of the deposit rather complex hydrogeology, it was decided to perform the task on the basis of numerical geohydraulic modelling using finite difference method (FDM) in the environment of Visual MODFLOW software tools. The paper describes the following steps of works performed within the project: input data acquisition, processing and analysis; creation of concept-based hydrogeology model; development of hindcasting numerical model; model calibration in the context of environmental conditions and actual mining operations hosted within the open-pit; sensitivity analysis and advanced simulation to develop the forecasting numerical model. When performed, the forecast value in terms of groundwater inflow to the pit has been calculated. Thus, pit groundwater level at the end of mining operations has been developed. Following a number of scenarios applied, model sensitivity analysis has been made and this provided the basis to identify the factors that have the most essential impact on water inflow to the pit.

Environmental assessment of water management and urban growth: A case study in an Argentina Pampean plain's basin

Urbanization has been identified as one of the issues with the greatest environmental impacts on water resources. This study aims to make an environmental diagnosis of urban water management with a systematic approach in a basin with great hydrogeological complexity. We have analyzed urban water management in the Langueyú basin, Argentina, in the period comprehended between 1940 and 2015 in which the city has had a disordered urban growth. It showed that the lack of integrated management together with urban expansion have resulted in a process of building densification and infrastructure that favors the recurrence and magnitude of exceptional hydrological events. This has been accompanied by a spatial displacement of these events and a lack of sanitary services with the same sense of urbanization. It was also demonstrated that the lack of integrated water management this not only had consequences on the Tandil city services associated with the urban hydrological cycle, but also on the quality of its surface water resources (contamination of streams in its urban section) and groundwater (elevation of nitrates levels in water from wells water supply). The absence of a systemic approach to the problem has not considered the relationships between the subsystems involved in water management. This management has been based mainly on the application of structural measures. The main non-structural measure carried out has been to expand the regulations and some neighbor's struggle movements. Other non-structural measures promoted by several actors involved in urban water management, such as authorities, should be carried out in order to raise awareness amongst the population on the importance of water resource protection, especially in areas with hydrogeological limitations.

Current hydrogeochemical profile of groundwater in the Middle Jurassic hydrogeological complex of the Lyaminsky oil and gas field

The aim of the study is to identify the influence of some parameters of the geological environment on the formation of the current hydrogeochemical profile in the Middle Jurassic hydrogeological complex (layers YU2-4) of the Lyaminsky oil and gas field in Western Siberia.The factors controlling the changes in the chemical composition of the groundwater (geotemperatures, influence of neotectonics, etc.) after the process of sedimentation and water accumulation were analysed on the basis of the lithogenetic theory of the transformation of the composition of groundwater during geological evolution. In the course of the research, correlation coefficients were obtained for the value of groundwater mineralisation in the complex with the modern and paleotemperatures of the Tyumen suite, the porosity coefficient and the depth of the foundation. The obtained results allowed assuming that the current hydrogeochemical profile of the Middle Jurassic hydrogeological complex is the result of the consistent action of the whole complex of factors. The results of the analysis showed that the influence of neotectonic processes on the current hydrogeochemical profile is quite probable. The reasons for the heterogeneity of mineralisation, apart from neotectonic processes, may be different, but in any case, the identification of relationships such as "Mineralisation - a parameter of the state of the geological environment" indicates a change in the concentration of salts in groundwater after their accumulation together with sediment.

Hydrogeologic Constraints for Drinking Water Security in Southwest Coastal Bangladesh: Implications for Sustainable Development Goal 6.1

Transitioning from the Millennium Development Goals (MDG) to the Sustainable Development Goals (SDG) is a big challenge, particularly for SDG 6.1, as the effective delivery of drinking water services drops due to more stringent indicators, especially for water quality constraints. Salinity in groundwater has received less attention compared to arsenic and E. Coli in the MDG era, while its presence and widespread variability has considerable implications in larger coastal areas for achieving SDG 6.1 targets. This article analyzes drinking water security in southwest coastal Bangladesh, through an in-depth field investigation. It reveals that the exponential growth of groundwater-based technologies, such as tube wells, does not necessarily indicate the actual safe drinking water coverage in coastal areas, due to complex hydrogeology with the high spatial variability of groundwater salinity risks. The spatial variability of hydrogeologic constraints and groundwater salinity risks also reinforces concerns of access, reliability, and affordability with different water supply technologies. National estimates can be misleading as the presence of salinity substantially lowers the effective drinking water coverage. Infrastructural investments for drinking water supply need to consider a sound knowledge of hydrogeologic heterogeneity, and the monitoring of water quality, if the SDG 6.1 targets are to be met.

Geology and land use shape nitrogen and sulfur cycling groundwater microbial communities in Pacific Island aquifers

Resource-constrained island populations have thrived in Hawai’i for over a millennium, but now face aggressive new challenges to fundamental resources, including the security and sustainability of water resources. Characterizing the microbial community in groundwater ecosystems is a powerful approach to infer changes from human impacts due to land management in hydrogeological complex aquifers. In this study, we investigate how geology and land management influence geochemistry, microbial diversity and metabolic functions. We sampled a total of 19 wells over 2-years across the Hualālai watershed of Kona, Hawai’i analyzing geochemistry, and microbial communities by 16S rRNA amplicon sequencing. Geochemical analysis revealed significantly higher sulfate along the northwest volcanic rift zone, and high nitrogen (N) correlated with high on-site sewage disposal systems (OSDS) density. A total of 12,973 Amplicon Sequence Variants (ASV) were identified in 220 samples, including 865 ASVs classified as putative N and sulfur (S) cyclers. The N and S cyclers were dominated by a putative S-oxidizer coupled to complete denitrification (Acinetobacter), significantly enriched up to 4-times comparatively amongst samples grouped by geochemistry. The significant presence of Acinetobacter infers the bioremediation potential of volcanic groundwater for microbial-driven coupled S-oxidation and denitrification providing an ecosystem service for island populations dependent upon groundwater aquifers.

Interpreting Mine Water Sources and Determining Mixing Ratios Based on the Spatial and Chemical Characteristics of Bedrock Brines in a Coastal Mine

Water inrush caused by mining below the seafloor seriously affects the safety and production of mines. Identifying the end element of mine inrush and accurately calculating the mixing ratios of end elements are the basis for a reasonable evaluation of water inrush risk. Based on hydrogeochemical and stable isotope indexes, combined with the spatial distribution characteristics of brine, the classification of brine in the study area was preliminarily determined as follows: shallow brine, middle brine, and deep brine (while previous studies have only classified bedrock brine as one category). Hierarchical multi-index analysis was used to identify the inrush end elements in the different sublevels, and an end-element mixed model was determined according to the analysis results of the four pairs of evaluation indexes (Cl−–δ18 O, Cl−–Ca2+, Cl−–Mg2+, and Cl−–Na+). Through a comparison with the deviation analysis results of previous studies, it was shown that this method is suitable for mine-water-source identification when under complex hydrogeology conditions. According to the calculation results of the mixing ratio, the seawater ratio shows, within the mining process, a trend of first increasing, then decreasing, and finally stabilizing. This trend is controlled by disturbance stress, self-weight stress, and tectonic stress. The vertical zonation of the seawater proportions indicates that seawater mainly recharges mine water through vertical fractures. The difference in the proportion of seawater at the water inrush points of the −600 m sublevels indicates that the F3 fault and the northwest water-conducting fracture zone may be the preferred flow channels for seawater to recharge mine water. The research results are of great significance to promote the safe mining of coastal mines around the world.

Simulation-Optimization Approach for Siting Injection Wells in Urban Area with Complex Hydrogeology.

Managed aquifer recharge has become a standard water resources management practice to promote the development of locally sustainable water supplies and combat water scarcity. However, installation of injection wells for replenishment purposes in urban areas with complex hydrogeology faces many challenges, such as limited land availability, potential impacts on municipal production wells and known subsurface contamination plumes, and complex spatially variable hydraulic connections between aquifer units. To assess the feasibility and cost-effectiveness of injecting advanced treated water (ATW) into a complex urban aquifer system, a Simulation-Optimization (SO) model was developed to automate a systematic search for the most cost-effective locations to install new wells for injecting various quantities of ATW, if feasible. The generalized workflow presented here uses an existing MODFLOW groundwater model-along with advanced optimization routines that are publicly available-to flexibly accommodate a multiobjective function, complex constraints, and specific project requirements. The model successfully placed wells for injection of 1 to 4 MGD of ATW in aquifers underlying the study area. The injection well placement was primarily constrained by avoiding excessive impact on environmental sites with underlying groundwater plumes. The largest costs were for well installation and piping to the wells from the existing ATW pipes. This workflow is readily adaptable to other sites with different complexities, decision variables, or constraints.

Bicarbonate waters in hydrogeological complexes of the hypergenesis zone of the Southern Cis-Urals

The article deals with the formation and distribution of bicarbonate groundwater in the hydrogeological complexes of the hypergenesis zone of the Southern Cis-Urals. Particular attention is paid to the issues of the distribution of bicarbonate groundwater in the hydrogeological section, which are of the greatest practical importance for the purposes of drinking water supply in the region. On the basis of long-term complex field and experimental studies, it has been established that the formation of the chemical composition and distribution of these waters in hydrogeological complexes is subject to the laws of vertical hydrogeodynamic and gas-hydrochemical zonality. The influence of technogenesis on the qualitative composition of these waters is noted.

Geofluid dynamic conditions in the subsalt complex of productive horizons in the northern part of the Nepa-Botuoba oil and gas region

The article considers the geofluid dynamic state of productive horizons of the subsalt hydrogeological complex with large-scale of subnormal pressure formation. An ordered change in the hydraulic potential along the section is noted, indicating that all the selected permeable formation in the established sediments belong to a single geofluid dynamic system. The energy state of the reservoir fluid system at the regional and local level is proven to directly affect the dynamics of gas fluids and, consequently, the formation of oil and gas deposits. Thus, the processes of secondary reformation of gas deposits occurred in the subsalt hydrogeological complex of the northern part of the Nepa-Botuoba oil and gas region. The subnormal pressure zones serve as gas-collecting areas during vertical and lateral migration of gas fluids.

Hypogene speleogenesis related to porphyry magmatic intrusions and its influence on subsequent karst evolution in the Peruvian high Andes

Carbonate rocks of Cretaceous and Jurassic age are widespread in the Peruvian Andes where they host numerous magmatic intrusions and related ore deposits. Most of Peru's metal ore deposits are located at high elevations within a narrow, tectonized carbonate-rock belt extending over 2000 km in length. Many of the limestone formations are karstified and characterized by high recharge and percolation rates, well-developed subsurface drainage and complex flow patterns. Knowledge of karst in the Andes is generally limited, although karst is recognized to cause extreme hydrogeologic complexity and great challenges in development of mining facilities located in carbonate settings. Aspects of the origin of void/conduit systems (i.e. speleogenesis) and karst evolution are rarely addressed in environmental impact and risk assessment studies.This study in the Antamina area in the east side of the Cordillera Occidental, home to the world largest known skarn copper‑zinc deposit, demonstrates that the current karst system has formed as the result of polygenetic and multi-phase development. Structure-controlled hypogene cave systems are well-preserved and widespread in the area and present a foremost example of endogenous hypogene speleogenesis related to magmatic intrusions. Hypogene karst structures have strongly influenced subsequent epigene karstification, which commenced at the Pliocene-Pleistocene boundary. Changes in the base-level position due to the landscape evolution and Pleistocene glaciations were major additional factors that influenced epigene karst development. The findings of this study are potentially relevant to assessing karst origin and hydrogeology in many carbonate-hosted ore deposits in the Peruvian Andes and other regions. This study shows that the speleogenetic and evolutionary approach is indispensable in the development of sound conceptual models of groundwater flow in karst terrains and the assessment of karst-related hazards and risks.

Introduction of advanced water management technologies in the Orenburg mining region

The Orenburg Region is rich in various minerals. Dozens of oil and gas fields are being developed on its platform sediment part, while the mountain-folded areas hold deposits of non-ferrous, ferrous and precious metals, rare and radioactive elements, bituminous coal and lignite, and non-metallic minerals. Huge land areas are disturbed by mining, occupied by stock piles of waste rocks and lowgrade ore, and are polluted with spills of oil and deep brines. The economic development of the region is accompanied with an increase in pollution and depletion of water resources. Wide distribution of alkaline land, saline-alkali soils and granitoids containing radon and toxic products of its decay aggravates the impact on the regional hydrosphere. In this regard, it is necessary to study the complex hydrogeology in the region and to evaluate the water quality. The important problems to be solved include: development of the reservoir appraisal methodology; chemical and bacteriological analysis of water and its sensitivity to secondary salinization processes and relics of the marine salt complex; substantiation of water spreading and contamination prevention technologies. The developed recommendations are meant to reach the objective of introduction of modern water management technologies into production as per the resolution of the Russian Government. The article discusses feasibility of water management technologies as a case-study of the Svetly district of the Eastern Orenburg region and the Orenburg urban agglomeration, and necessitates recommendations for their implementation under diverse conditions within the Orenburg Region. As a result of the methodological approach, calculations and modeling of the situation in the mining areas of the Orenburg Region, the effectiveness of the technology of water spreading by means of accumulation of flood water in the local river is proved. The water spreading approach using the active water intakes and conservation reservoirs can increase the productivity of operating wells by 1.5–2 times, enable avoiding depletion of the aquifer and allow meeting the needs of the Orenburg Region’s population in drinking water.