Hydrogeological Basin Research Articles

Hydrogeological conditions of the Megionsky oil field

The aim of this study is to provide a comprehensive description of the underground hydrosphere of the Megionsky oil field. The field is located within the well-studied West Siberian megabasin. According to V. M. Matushevich's classification (1986), the stratigraphy of the Megionsky field is divided into three overlapping hydrogeological basins (Cenozoic, Mesozoic, and Paleozoic). The results of the analysis of the variation in water mineralization, formation pressures, and geothermal gradients with depth have justified the classification of the Megion oil field as a water-bearing system of the elision-type geodynamic origin. The aquifers and water-bearing complexes in the study area extensively utilized for drinking, domestic, and industrial water supply. Additionally, the Aptian-Albian-Cenomanian hydrogeological complex of the Mesozoic basin is also targeted for the disposal of excess associated water. These factors indicate a significant anthropogenic impact on hydrogeological systems. Understanding the hydrogeological features of the underground hydrosphere provides a foundation for designing measures to protect fresh and mineralized groundwater from contamination and depletion.

Delineation of a conceptual groundwater flow model of the Kandi basin in Benin (West Africa): Insights from isotopes, piezometric and hydrological investigations

Study regionThe hydrogeological Kandi basin, the Benin’s sector of the transboundary Iullumeden basin, located in northern Benin, West Africa Study focusIn many parts of the world, groundwater resources constitute the main, if not the only, source of potable water available to address a growing demand for numerous uses. And yet, a basic understanding of the hydrogeology of many critical groundwater systems is lacking in many instances. Only when severe groundwater depletion or serious groundwater quality issues arise is the attention paid to the lack of specific groundwater studies. This study targets the Kandi basin, a ∼8700 km2 hydrogeological basin located in northern Benin, which is the primary source of potable water for its inhabitants, but its hydrogeological functioning remains unclear. We conducted isotopic and hydrogeological investigations in this basin from 2013 to 2019 to characterize groundwater recharge processes and delineate flow patterns. The resulting hydrological and geochemical data have been integrated and interpreted using tools including mapping tools. New hydrological insights for the regionThis study has identified the preferential groundwater recharge areas and characterized the main groundwater flow paths. Predominant areas of groundwater dischage into surface water, regardless of the seasons, were detected and areas where the surface-groundwater interflows are season-dependent were discriminated. The main findings presented in this paper are expected to provide a baseline for further in-depth hydrogeological investigations, namely groundwater flow modeling that will help understand the impacts of various groundwater withdrawals and climate changes on the groundwater resources availability of this basin.

GROUNDWATER VULNERABILITY MAP OF BASARA BASIN, SULAIMANI GOVERNORATE, IRAQI KURDISTAN REGION

The Basara basin which is one of the most promising hydrogeological basin in Iraqi Kurdistan Region, located in north east of Iraq, 25 km west of Sulaimani city, between the 496652 - 537752 East and 3911038 - 3951906 North in Universal Transverse Mercator (UTM) and lie in Zone 38N. The basin has a rectangular shape and covering an area of 571 km². The present hydrogeological investigations have revealed three inhomogeneous and anisotropic water bearing formations: Eocene Karstic Fissured Aquifer (EKFA), Intergranular Aquifer represented by Alluvium and Pliocene (AIA) & (PIA), as well as Miocene Complex Aquifer (MCA).For the first time, not only in Kurdistan but also in Iraq, Groundwater Vulnerability Map has been constructed in this study, using DRASTIC method with the assistance of Geographic Information System (GIS) to show zonation area of high and low groundwater susceptibility to pollution. Accordingly, vulnerability classes of the study area were classified into four classes. Most of the basin shows the highest extension of the zones with very low and low vulnerability zones, in contrast the zones with high vulnerability are distributed mainly in the mountain areas, solely in the eastern Uloblagh and Kuwaik mountains, in addition to that small zones in the farthest northern corner and south western corner of the area have less or no human activity.

ГЕОХИМИЧЕСКИЕ ПОСЛЕДСТВИЯ ЗАХОРОНЕНИЯ УГЛЕКИСЛОГО ГАЗА В ТЕРРИГЕННЫХ КОЛЛЕКТОРАХ

The paper is aimed at the research practice on identifying the features of interaction in the water-rockcarbon dioxide system in relation to terrigenous reservoirs, widely occurring in hydrogeological basins in the territory of the Russian Federation and potentially suitable for the placement of carbon dioxide. As the CO2 solution is saturated, along with an increase in total dissolved solids there is a naturally-determined increment in the volume of transition of ions into their complex forms. The main macro components (Ca2+, Mg2+, Na+, K+, (SO4)2–, Cl– ) migrate mainly in the form of their own ions, with a decrease in their fraction by an order of 1–3 % with an increase in mineralization. Ions such as Fe, Al3+, Mn3+, (NO3)–, (HCO3)–, SiO2, (NH4)+, (NO2)– are prone to transition into the form of complex compounds, the fraction of which in the total volume increases with the amount of saturation of solution with carbon dioxide. When CO2 is injected into the terrigenous reservoir, there is a natural decrease in the solution pH, absence of precipitation of carbonates and minimal changes in the rock porosity. The observed process of dissolution of primary aluminosilicate minerals (albite, anorthite, potassium feldspar) is characteristic of most of the considered mineralogical varieties of reservoirs, when they are saturated with CO2. This process is accompanied by deposition of secondary mineral phases in the form of montmorillonites, illites, chlorites, etc. Taking into account the low rates of these reactions, no significant changes in reservoir properties are noticed.

Magnesium and groundwater flow relationship in karst aquifers: a tool for exploitation management of springs

Karst aquifers are characterized by different types of groundwater flow, related to different types of permeability due to the simultaneous presence of matrix, fractures and conduits. The presence of a well-developed karst conduit system leads to a rapid circulation of groundwater within the aquifer and a pulse-type response of the spring flow to the rainfall inputs, with a potential fast transport of contaminants from the hydrogeological basin surface to the discharge zones. Supported by hydro chemical analyses of spring water samples and single discharge measurements, it was possible to develop specific mass balance models, correlating ion content to spring flowrates. Specifically, Mg2+ content revealed a reliable application for spring baseflow separation in karst settings. Once the local model has been set, its conservative behaviour, in mostly limestone-dominant aquifers, allows using Mg2+ as a natural tracer of groundwater flow, distinguishing conduit flow (overflow) and diffuse flow (baseflow) occurrence in the spring outlet, without additional discharge measurements. In karst settings, the difficulty in continuously monitoring the spring discharge values makes this application interesting for exploitation management. This study shows the results obtained for two springs located in Central Italy, confirming that monitoring groundwater quality in karst environments is often the key for successfully characterizing springs and assessing the total yield when direct measurements are not available.

ASSESSMENT OF THE HYDROGEOLOGICAL CONDITIONS OF THE KARABAGH-MIL PLAIN

Mil-Karabagh plain, the studied territory, located to the north-east from the piedmont of the Lesser Caucasus. The main irrigation canals of the region, including the bed of the Yukhari-Karabagh canal, have high water permeability, as they are built from local soils. This ensures that surface and underground waters interact, feeding each other along the flow. The amount of precipitation in different parts of the Karabagh plain was 370-453 mm, and they fall unevenly in different seasons. Thus, the maximum amount of precipitation is observed in autumn and spring, and the minimum amount of precipitation is observed in winter and summer. There are 6 aquifers (water-bearing horizons) in the upper part of the Mil plain: 1 underground, 5 confined aquifers. The underground and three confined aquifers are associated with the Quaternary period, the fourth aquifer is associated with the Absheron, and the fifth with Aghjagil stages sedimentary rocks. The variability of the level mode is fully studied here. Sources of formation of underground water resources and methods of their effective use have been identified to a sufficient level. The horizon of underground waters and water strikes form a single water horizon in the elevated parts of river tributaries. The water deposits mentioned here are composed of boulder-gravel-pebble stones according to their lithological composition, clay and clayey deposits are rare. These deposits are found at depths of up to 110 m and more. The degree of natural drainage of the territory is one of the main factors influencing soil reclamation, depending on the geological structure, geomorphological conditions and features of the relief. The Karabagh irrigation massif is served by the Mil-Karabagh reservoir. Which discharges drainage water with an average mineralization of 12.7 g/l to 200 million m3 per year. Occurrence depth of the groundwater within the territory of the Karabagh irrigation massif 0-10 m and deeper from surface. There is a tendency to decrease the depth of groundwater in the area from the south-west to the north-east, i.e. from the piedmont to the Kura river. Keywords: underground water, rural economy, drainage, water strikes, hydrogeological basin.

Groundwater sustainability in the Friuli Plain

Groundwater resources in the Friuli Venezia Giulia (FVG) Region (northeast Italy) are an important natural wealth in terms of quantity, quality and ease of supply. This optimal condition, however, has long believed that it allowed an irrational and uncontrolled exploitation that inevitably produced tangible consequences on the water resources availability.The goal of the present research is the evaluation of the sustainable use of the groundwater in the Friuli Venezia Giulia Region aimed at providing guide-lines for its rational use. The study area belongs to the hydrogeological basin of the Friuli Plain and includes part of Veneto Region and Slovenia. The plain area is divided in two parts: the High Plain (HP) characterized by a phreatic aquifer and the Low Plain (LP) where eleven confined aquifer systems were identified. The two physiographic zones are separated by the spring belt. In order to evaluate the groundwater avaliability, a 3D model of the Low Friuli Plain aquifer systems was realized using Rockworks R14 software, starting from 603 lithostratigraphic wells data. Isobath and isopach maps were elaborated using kriging geostatistical method. Precipitation, evapotranspiration, runoff and infiltration were calculated to evaluate the inflow and outflow groundwater budget terms (109 rainfall and 46 thermometric stations, time series 1979-2008). To better define the river influences and the outflows at sea, a series of recent surveys on river discharges and surface withdrawals were considered. To obtain the water-budget in non-natural conditions, as the currents, were taken into account the groundwater withdrawals that were evaluated for each type of use and for each aquifer systems, starting from 2 geodatabases: one for the domestic uses (50101 estimated wells) and one for the industrial, agricultural, fish breeding, hygienic, geothermal and other minor uses (7594 wells). Well withdrawals amount were evaluated on annual base for recent periods and expressed as m3/s. The total current estimated groundwater withdrawals reach 62.4 m3/s, of which 41.1 m3/s from the confined aquifer systems in the LP area. More than 52% of the withdrawals are due to the domestic wells. For the water-budget, the studied territory was considered a “semi-closed box” in which groundwater sharings with the neighboring areas are not relevant and where the recharge is mainly due to the influent character of the river, infiltration, rainfall and irrigation practices. As result, the waterbudget for the confined LP is equal to +2.6 m3/s representing the accuracy, fairly acceptable for the scale of the research. Withdrawal entity, spring belt discharge, phreatic levels and confined aquifer’s pressure are closely interdependent and in dynamic equilibrium. The sustainability comes from the consistency and ratio between recharge and withdrawals. The confined aquifer withdrawals in the LP represent the 23.1% of the groundwater recharge coming from the HP and the 30.6% of the spring belt discharge. Seen that this last one can not further decrease, unless loss of important ecosystems, is likely to think that the present situation can be defined of limit equilibrium.

Changes in Groundwater Levels and its Salinity (Badra Basin Iraq)

A fact that human-induced greenhouse gas emissions have led to an increased frequency and/or intensity of some weather and climate extremes since pre-industrial time, in particular for temperature extremes which affected lots of regions by reducing precipitations. Accordingly, this reduction causes a lowering of groundwater levels which was adopted as a goal of this study and its effects on quality of it. The study area is Badra - Jassan basin located to the north of Kut city, the center of Wasit governorate, and bordered by the international boundary with Iran from the east and northern east covering an area of about (1020) Km2. Badra - Jassan basin is an important hydrogeological basin in which groundwater can be used for agricultural purposes; especially with decreasing surface water supply. The research studied a predictive mathematical model of groundwater by ten wells distributed randomly within the boundaries of the study area; all of them fall within the unconfined aquifer the mathematical model for the study area has been developed using the Geographic Information System (GIS) software. The Groundwater level map for the ten existing wells was drawn from data in (2021) and a comparison with else published in (2002) for the study area. Likewise, the salinity concentration map variations for the same periods were estimated. The present study showed a decline in groundwater levels which conjunction with an Increasing in the range and value of groundwater salinity concentrations.

ON THE POSSIBILITY OF IMPLEMENTING CCS PROJECTS IN THE CARBONATE RESERVOIRS OF THE SIBERIAN PLATFORM

Link for citation: Nikitenkov A.N., Novikov D.A., Maksimova A.A., Penigin A.V., Varaksina I.V., Zhukovskaya E.A. On the possibility of implementing CCS projects in the carbonate reservoirs of the Siberian Platform. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 8, рр. 68-78. In Rus. The relevance. Carbon capture utilization and storage technology involving geological storage of carbon dioxide in deep aquifers is widely used in the world as this technology is aimed at decreasing the emission of greenhouse gases into the Earth’s atmosphere and minimizing the influence of these gases on the global climate change. Objective: to carry out preliminary investigation of the features of water – rock – carbon dioxide interactions in application to carbonate collectors, which are widespread in hydrogeological basins over the territory of the Russian Federation and are potentially suitable as carbon dioxide storage facilities. These processes are considered by the example of the ancient Siberian Platform, where industrial production of hydrocarbons is currently increasing, and a series of large-scale projects in the area of petroleum and gas chemistry are under implementation. Methods. Mathematical physical and chemical modeling was applied to solve the problem. The calculations were implemented by the HydroGeo software package, in which the achievement of chemical equilibria for the «water–rock» system is implemented on the basis of the method of equilibrium constants. Results. The obtained results allow us to evaluate the directions of geochemical processes in the collectors under consideration and to provide qualitative estimation of changes in the pore space under the conditions of its saturation with carbon dioxide, with respect to different saturation degrees. It is established that solution acidification is observed as a result of its saturation with СО2, with the transition of chemical elements to the prevailing forms of complex ions bound with hydrocarbonate and chloride ions (Mn, Na, K). At the same time, saturation with carbon dioxide does not have so substantial effect on the forms of Ca and Fe migration. Special attention is attracted to Al, which is transformed almost completely from complex forms into Al3+ in the presence of carbon dioxide. In the studied reference samples, rather intense transformation of collector rocks with redistribution of elements between the primary and secondary mineral phases is observed (both rock dissolution and precipitation up to several hundred g/dm3) with comparatively small absolute changes in open porosity. In a series of the considered objects, the dissolution of calcite and dolomite proceeds due to a decrease in pH. The directions of transformations, as well as the trend of changes in filtration-capacity properties, are determined by the specific mineralogical combination of collector rocks and the brine present in them, as well as by the stage of evolution of the system under consideration (the first part of the considered combinations is initially far from the equilibrium and continues interacting, while the second part is close to the equilibrium and is transformed into non-equilibrium state due to saturation with carbon dioxide).

Influence of the Meso-Cenozoic tectonics on groundwater and surface water flows in the Skoura hydrogeological basin (folded Middle Atlas, Morocco)

The Skoura hydrogeological basin, part of the Folded Middle Atlas Mountain range, is located 30 km NE of Boulemane city and 50 km SE of Sefrou city. It is limited to the North and North-East by the Aichoun reliefs, to the West by the North Middle Atlas Fault (NMAF) and to the South by the Tichoukt ridge. It corresponds to a collapsed area resulting from polyphase tectonics succeeding from the Upper Miocene to present day. Its location between two major structural lines favors the accumulation and runoff of all precipitated water. This work aims to identify the geological structures which guide groundwater and surface water flows. The geological mapping and the measurements of the water points capturing the water table, have allowed to reconstitute the geodynamic evolution of this basin on one hand, and to identify the various aquifers containing the water table on the other hand. The Skoura water table circulates within four aquifer systems represented by Liassic carbonates, Bathonian sandstones, Vallesian lacustrine limestone and the Plio-Quaternary fluvio-lacustrine deposits. The impermeable substratum of each reservoir layer is respectively represented from bottom to top by Triassic-Liassic red claystones, Bathonian versicolored marls, Vallesian lacustrine claystones and Upper Miocene marls. The superposition of the piezometric map with the fracturing map shows that the groundwater flow axis is multidirectional. Groundwater flows along faults and fracture, following two main directions converging towards the Mdaz River. A first flow from SW to NE characterizing the upstream part of the hydrogeological basin and a second flow from West to East which covers its central part. Concerning surface water flows, they are guided by the submeridian and transverse faults, as well as by the two major faults (NMAF and the Tichoukt Fault) which have played a major role in the genesis and evolution of the Oued Mdaz valley.

Application of fuzzy C-means clustering and fuzzy EDAS to assess groundwater irrigation suitability and prioritization for agricultural development in a complex hydrogeological basin.

The current research is focused on detecting a river basin suitable for agriculture and priority for management using a new clustering tool of groundwater quality with fuzzy logic technique in R and Geographical Information System. A new fuzzy clustering-soft computing technique has been executed to determine the different hydrochemical zones considering 13 essential parameters such as electrical conductivity, hardness, chloride, sodium adsorption ratio, residual sodium carbonate, soluble sodium percent, magnesium hazard, permeability index, potential salinity, residual sodium bicarbonate, Kelly's ratio, synthetic harmful coefficient, and exchangeable sodium percentage. The derived fuzzy C-mean clustering (FCM) outperformed other available hard computing techniques like hierarchical clustering, K-means clustering, and agglomerative clustering. It divided the sampling sites into 2 clustering groups (FCM I and FCM II) which has been validated using fuzzy silhouette index (0.85), the partition coefficient (0.76), the partial entropy (0.68), and the modified partition coefficient (0.52). The hydrogeochemical analysis confirmed that the rock-water interaction, chemical weathering, and ion exchange process are predominant in the aquifer system of the study area. According to the correlation plots, the studied groundwater samples largely evolved from [Formula: see text], mixed [Formula: see text] types, and [Formula: see text] types. The spatial distribution map and the hydrochemical analysis also gives a clear depiction of the fluoride (> 1.0mg/l) and high iron (> 0.3mg/l) contamination in groundwater quality, making it unsuitable for both drinking and irrigation. A fuzzy EDAS priority map has been prepared based on all the irrigation suitability parameters which concludes that the groundwater at the upstream and downstream section of the basin requires the most attention. Based on the highest priority for management, five zones have been delineated: very high (5.98%), high (22.31%), medium (16.39%), low (32.30%), and very low (23.02). The findings of this study will be beneficial to planners and policymakers as they can develop schemes to solve similar problems across the country.

Evaluation of Efficiency of Groundwater Desalination Plants in Different Hydrogeological Conditions in Salahaddin Governorate/ Iraq

Five groundwater desalination plants elected in the province of Salahuddin, these plants are Rimth, AlRaml, Albo Hamed, Albo Rahil, and Mcelila which supplied from Al-Naamah, Zgiton, Baiji-Tikrit, West Samarra, and West Makhoul hydrogeological basins respectively. Hydrogeological, hydraulic and hydrochemical characteristics of the five sub- basins were reviewed, it is found that the selection of the locations of these stations did not depend on certain criteria, especially the hydrochemical parameters which are the principal in the desalination. So, there are a lot of wells in these sub-basins, have best quality than the supply wells of the stations under study. 17samples were collected for selected desalination stations, three or four samples for each station included raw water (well water), desalinated water, mixed desalinated water, and rejected water, the field and laboratory tests were conducted on the different types of sampled water, the concentrations of more than seventy element were measured, included major anions and cations, minor and trace elements, the results were compared with local and international standards for drinking water. it is found that the raw water unsuitable for human use, the desalinated and mixed desalinated water are within the allowable limits of these standard, but these standards ignored most of the trace elements which were not discussed in the documents that annexed with these standard, and did not specify the permitted upper limits, despite the that some of these elements increases in the desalinated water in comparison with the raw water, light has been focused to the negative effects of these elements on public health. The efficiency of desalination evaluated for these stations depending on the qualitative standards, then, the qualitative criteria were adopted for quantitative evaluation, and show that the stations with high efficiency, its efficiency in removing dissolved solids (TDS) ranged between (81.31% - 98.18%), regarding to quantitative desalination efficiency, the percentage of desalinated water to the raw ranged between (29% -70.37%).

Reaction of the carbonate Sibillini Mountains Basal aquifer (Central Italy) to the extensional 2016–2017 seismic sequence

Hydrogeological perturbations in response to earthquakes are widely described worldwide. In carbonate aquifers, a post-seismic discharge increase is often attributed to an increase of bulk permeability due to co-seismic fracturing and the attention on the role of faults to explain the diversion of groundwater is increasing. We focus on the reaction of carbonate hydrogeological basins to extensional seismicity, taking as an example the effects of the Central Italy 2016–2017 seismic sequence, on the Basal aquifer of the Sibillini Mountains area. Geo-structural, seismological and ground deformation data were collected and merged with artificial tracer tests results and with a 4-years discharge and geochemical monitoring campaign. The main NNW-directed groundwater flow was diverted to the west and a discharge deficit was observed at the foot-wall of the activated fault system with a relevant discharge increase, accompanied by geochemical variations, at the fault system hanging-wall. The observed variations are consistent with the combined action of a permeability increase along the activated fault systems, which modified the predominant pre-seismic along-strike regional flow, and with hydraulic conductivity increase due to fracturing, determining a fast aquifers emptying. We show that the prevailing mechanism depends on the aquifer systems position with respect to the activated faults.

Calculation of Potential Groundwater Resources in Orkhon River Basin

Available groundwater research work and data levels are very limited due to the wide territory of our country. Potential Groundwater resources need to be calculated by basin to implement Integrated Water Resources Management Plans. For this purpose, previously the calculations were done twice in the Orkhon River Basin. The last calculation was done 10 years ago, therefore Integrated Water Resources Management Plan needs to be redeveloped, using updated research work and data levels. The Orkhon River is one of the biggest rivers in Mongolia, rising from Khangai Mountain Range and flowing into the Selenge River. The Orkhon River Basin includes the Tuul, Kharaa, and Yeruu rivers basins which rise in the Khentii Mountains. For the first time, a hydrogeological structure map of the basin was developed which analyzed and systemized the hydrogeological structure, the morphostructure factors, and the hydraulic properties of the hydrogeological formations distributed in the Orkhon River Basin. There are two types of hydrogeological basins and three types of hydrogeological massifs in the basin. This paper presents the calculation of the Potential Groundwater Resources (PGR) in the Orkhon River Basin based on groundwater well data, reports of groundwater exploration and research works, and the hydrogeological maps at a scale of 1:500,000. As a result of this calculation, there are 1.99 km3 of PGR in this basin.The largest resources are found in the linear intermountain hydrogeological basin which occupies 98 percent of the total PGR. Further improvement of the quality and standards of water research remains an important issue for hydrogeologists today.

Hydrogeochemical conditions of the Mesozoic hydrogeological basin within the Ravninnoe oil field

Studies of the hydrogeochemical features of groundwater in deep horizons of the West Siberian megabasin are important. They are closely related to applied and fundamental issues of oil and gas hydrogeology and allow studying the processes of formation, accumulation and migration of hydrocarbons.The article deals with our analysis of the hydrogeochemical conditions of the Mesozoic hydrogeological basin within the Ravninnoe oil field. The ion-salt composition of groundwater in deep horizons in the territory is variable. Basically groundwater are of the calcium chloride type (according to V. A. Sulin's classification), but magnesium chloride and sodium bicarbonate types of water are locally distributed. The hydrogeological conditions of the field are manifested in the change in the chemical composition of groundwater and in the vertical hydrochemical zonality. The article describes the features of the regional distribution of reservoir temperatures and reservoir pressures of the Aptian-Albian-Cenomanian, Neocomian and Jurassic hydrogeological complexes. The study of the formation factors of the hydrogeochemical field of these deposits was carried out taking into account paleotectonic, paleogeomorphological and paleohydrogeological reconstructions of the conditions that influenced the accumulation of fluids. Faults are widespread in the deposits of the pre-Jurassic complex, as well as angular unconformities between rocks of different ages, which predetermined the migration of hydrocarbons and the formation of their deposits.

Influence of infiltration regimes on hydrocarbon accumulation processes in Northern part of West Siberia

Background. Hydrogeological analysis is necessary for a comprehensive forecast of oil and gas deposits in any region. Early in the development of petroleum hydrogeology in the 1940–1970s, conditions for hydrocarbon (HC) accumulation were actively examined at depths of about 1–2 km, where meteoric waters often occur. However, for a long time, there was no interest in exploring petroleum basin infiltration systems despite the colossal hydrocarbon resources in West Siberia, Alberta (Canada), the Norwegian-Danish oil and gas basin (Norway) and Jungar Banner (China), which are associated with an infiltration hydrodynamic regime (IHR). The resumption of research into hydrocarbon systems controlled by IHR is advisable for theoretical and advanced applications in the exploration of hydrocarbon deposits, including non-structural hydrocarbon accumulation. This is essential for oil and gas fields with a long well production history, where the resources of hydrocarbon deposits associated with anticline structures have largely been exhausted.Aim. To elaborate on the influence of IHR on the HC accumulation processes, the evolution and preservation of these accumulations in the Northern part of West Siberia.Results. The authors discussed features of the infiltration system of the Northern part of the West Siberian hydrogeological basin and proved its unity within the onshore and offshore regions. It was shown that a specific feature of this basin consists in an internal discharge zone associated with the Gulf of Ob in modern plans. Based on analysis of hydrodynamic potentials within the Albian-Cenomanian complex, local accumulations of hydrocarbons, formed in the absence of control from the structural factor, were revealed.

EVALUATION OF RESERVOIR PROPERTIES OF THE CENOMANIAN AQUIFER SYSTEM AT SITES OF PRODUCED WATER PUMPING AS EXEMPLIFIED BY THE WEST SALYM OILFIELD IN WEST SIBERIA

The paper deals with one of the highly relevant problems arising from disposal of produced waters in West-Siberian oilfields. Produced waters are those co-recovered with oil. The water-cut factor (for oil) is well-known to reach 90% in West Siberia. This has led to widespread events for disposal of produced waters. Improving the procedures for prediction calculations of admissible quantity and quality of disposed waters is a topical problem in petroleum hydrogeology in West Siberia. This study reports a leak-off coefficient estimation for the Cenomanian deposits (the target ones for disposal of produced waters in most of oilfields across the region) of the Mesozoic hydrogeological basin. The calculation procedure widely used at present for a homogeneous confined aquifer does not reflect the true natural picture, as the aquifer into which the produced water is pumped is multilayered and heterogeneous. Here we look into natural processes for the formation of the West-Siberian megabasin, which have resulted in heterogeneous reservoirs: uncompensated sediment accumulation and present vertical fluid migration channels. Here we show that the gross thickness of the aquifer should be employed in leak-off and hydrodynamic estimations, and adduce the leak-off coefficient estimations for five oil wells in the West Salym oilfield based on the procedure suggested herein (factoring in the multilayered nature of the Cenomanian deposits). The average leak-off coefficient of sand streaks was 0.298 m/day, which we believe to reflect the natural condition of the aquifer more adequately than the standard estimation procedure used for a homogeneous confined aquifer.

Features of the subsurface water composition formation in the Mesozoic hydrogeological basin of the Middle Ob region fields

The formation of the deep oil and gas bearing horizons hydrogeological conditions in the Middle Ob region and the West Siberian megabasin as a whole contains many questions and is a subject of discussion. This is due to numerous hydrogeodynamic and hydrogeochemical anomalies that do not have an unambiguous explanation. The hydrogeological conditions feature of the area under consideration is inversion hydrogeochemical zonation in the Lower Cretaceous and Upper Jurassic sediments, as well as the presence of low-mineralized formation waters of hydrocarbonate-sodium composition. The change in the genetic type of waters, the mineralization decrease, the calcium ion content decrease and an increase in the hydrocarbonate ion amount in the Mesozoic hydrogeological basin, is associated with the transformation of mineral and organic matter in sedimentary rocks during their immersion, occurring at the elision stage of the basin development.

Interaction of fresh and submarine saline groundwater in the coastal zone of the Sea of Okhotsk and the Sea of Japan

The multidirectional interaction of fresh groundwater of land with a mineralization of 0.1 - 0.2 g/dm3 and submarine saline groundwater in the coastal zone of the western coast of the Sea of Okhotsk and the Sea of Japan has been characterized. The main hydrochemical background in the coastal zone of the seas is created by ultra-fresh and fresh hydrocarbonate groundwater of land in the free gravity runoff zone. The main types of submarine groundwater are silt sediment waters, pore-stratal and fissure-stratal waters of sedimentary rocks, fissure and fissure-vein waters of effusive, metamorphic and intrusive rocks. With the salinity of the modern sea waters within the range of 30-34.4 g/dm3, a decrease is traced from 27-30 g/dm3 in the sediments of the Upper Miocene-Holocene aquifer complex to 14-20 g/dm3 in the sediments of the Oligocene-Lower Miocene complex. Fresh groundwater of volcanogenic hydrogeological basins, the deposits of which have been explored in basalts, are distinguished by special advantages. These waters do not have environmental restrictions for drinking, they belong to the highest class and their resources may well be involved for a worthy use within the region and beyond.

EVALUACIÓN DE LA VULNERABILIDAD INTRÍNSECA A LA CONTAMINACIÓN DE LAS AGUAS SUBTERRÁNEAS EN LAS CUENCAS CUYAGUATEJE Y COSTERA SUR DE PINAR DEL RÍO, CUBA

Las cuencas hidrogeológicas Cuyaguateje y Costera Sur de Pinar del Río constituyen importantes fuentes de abasto de agua subterránea a la provincia de Pinar del Río en Cuba, por lo que es necesario el desarrollo de investigaciones que permitan la alerta temprana de su posible contaminación. El objetivo de este artículo fue evaluar la susceptibilidad a la contaminación de ambas cuencas subterráneas debido al impacto de contaminantes potenciales vertidos en su superficie. Por primera vez fue empleado en esta región el método de superposición de índices ponderados RISK. El mapa de vulnerabilidad intrínseca obtenido a escala 1:100 000 reveló que las zonas de moderada vulnerabilidad alcanzan el 55,1% de la región estudiada, y las zonas de alta y muy alta vulnerabilidad representan el 44,6%, resultados que se corresponden con la naturaleza geológica de las cuencas, con el diagnóstico ambiental de la provincia y con reportes de otros estudios realizados en la región. El método RISK demostró su elevado poder resolutivo y la factibilidad de su aplicación en otras cuencas del territorio nacional.