West Siberian Sedimentary Basin Research Articles

Crustal Subsidence in the West Siberian Sedimentary Basin Caused by Prograde Metamorphism-Induced Rock Contraction in the Lower Crust

Crustal Subsidence in the West Siberian Sedimentary Basin Caused by Prograde Metamorphism-Induced Rock Contraction in the Lower Crust

Evolution of the composition of Н, О and C stable isotopes in the groundwaters of oil and gas bearing sediments in the northern regions of West Siberia

The results of a study of the isotopic composition of oxygen and hydrogen of groundwater and dissolved inorganic carbon in oil and gas deposits of the northern regions of Western Siberia, covering a wide stratigraphic range – Mesozoic and Paleozoic are presented. The obtained values are very diverse, covering the intervals from –120 to –50‰ (δD) and from –17 to –2‰ (δ18O). Such a variable isotopic composition of waters indicates the absence of a unified mechanism for the accumulation of waters and their transformation during the geological evolution of the West Siberian sedimentary basin. The main feature of most of the studied waters is the pronounced values of oxygen isotope shifts relative to GMWL, which generally increase with the age of water-bearing deposits and reach 9‰, which indicates their ancient sedimentary origin. Variations in the isotopic composition of DIC (from –51.8 to +21.8‰) and its content in waters (from 0.2 to 38.6 mmol/I) indicate a wide range of water burial conditions and processes involved in the conversion of water-soluble carbon dioxide. A general pattern of changes in the isotopic composition of carbon in CO2 with time, expressed in general form by damped oscillations of the “isotope oscillator”, is revealed. A model of transformation of the carbon isotope composition in carbon dioxide in the closed cycle “atmosphere-soils-deep aquifers” for oil and gas deposits of the northern regions of Western Siberia based on the obtained isotope data is proposed.

Features of Using the Lithogeochemical Indicators for the Reconstruction of Paleoclimate and Composition of Demolition Sources in the Late Jurassic-Lower Cretaceous West Siberian Sedimentary Basin

Features of Using the Lithogeochemical Indicators for the Reconstruction of Paleoclimate and Composition of Demolition Sources in the Late Jurassic-Lower Cretaceous West Siberian Sedimentary Basin

The Origin of the West Siberian Sedimentary Basin without Strong Crustal Stretching: An Analysis of Superdeep Drilling Data

The mechanism of the formation of large sedimentary basins on the continents is among the main problems in geodynamics. The formation of such structures far from convergent plate boundaries is most often explained by intense stretching of the lithospheric layer (rifting). This should be followed by a large and prolonged crustal subsidence due to cooling of the stretched lithosphere. A characteristic feature of the post-rift subsidence is a decrease in its rate in time by several times over a hundred million years. Rifting in the West Siberian Basin was associated with the formation of Permian–Triassic graben-rifts. The subsequent (post-rift) subsidence is considered by many researchers as a cause of the formation of a thick layer of Mesozoic and Cenozoic sediments in the basin. Over the 86 Ma that passed from the beginning of the Middle Triassic to the end of the Middle Jurassic, the rate of post-rift subsidence should have decreased by about a factor of three. In fact, the opposite trend developed. Judging by the data of the Tyumen (SG-6) and En-Yakhin (SG-7) superdeep wells drilled in the northern part of the basin, the rate of crustal subsidence increased several times during this period of time. Such a sharp difference between the expected post-rift subsidence and the actual subsidence of the crust indicates that lithospheric stretching was not the main subsidence mechanism, and it could support only a small part of the subsidence. Under such circumstances, the main cause of the subsidence would have to be contraction of rocks in the Earth’s crust due to prograde metamorphism.

Reservoir simulation of the CO[formula omitted] storage potential for the depositional environments of West Siberia

We evaluate the CO2 storage potential for the depositional environments of the West Siberian sedimentary basin. Particularly, we investigate the prospect of storing large volumes of CO2 in the alluvial fan, barrier island, deltaic, and fluvial environments. We employ several detailed 3-D models of petroleum reservoirs as proxies for the saline aquifers occurring in the basin under the listed environments. By simulating supercritical CO2 injection into several reservoir sectors, we compare the environments in terms of their prospects for the underground storage of CO2. We estimate the maximum capacity and storage potential for the entire sectors by considering them the resources licensed for an industrial-scale Carbon Capture and Storage (CCS) project. The scenarios with a single and multiple injection wells are assessed in the evaluation, which might be of interest for the elaboration of feasible regulations and policies in the area. We find out that the barrier island deposits are characterized by maximum potential, whereas the fluvial environments are the least suitable for deploying CCS. We demonstrate that for the barrier island environments, the storage potential is most sensitive to the relative permeability end-points. We also test several scaling concepts for extending our estimates for a single-well injection to a multi-well scenarios and generally from a site-specific to regional scale. We conclude that due to the interference between nearby wells, the storage potential for a single well scenario cannot reliably be scaled to the case of CO2 injection through a group of wells.

Jurassic and Cretaceous clastic petroleum reservoirs of the West Siberian sedimentary basin: Mineralogy of clays and influence on poro-perm properties

• Kaolinite is a predominant clay for Jurassic while chlorite for Cretaceous reservoirs. • Secondary chloritization might not have affected the coarse-grained lithic clasts . • A lowland relief predominated in Jurassic and volcanic upland relief in Cretaceous. The West Siberian Sedimentary Basin (WSSB) is the main commercial and the biggest sedimentary basin of Russia and plays a huge role in the Russian oil and gas industry. Three deep wells intersecting full sections of the basin main Jurassic and Cretaceous reservoirs have been studied. This basin consists of two major petroliferous sedimentary sequences: uppermost is of Lower Cretaceous (the Neocomian Sedimentary Sequence) and the oldest petroliferous sandstones of Jurassic age (the Urman-Togur-Tyumen sequence). All the main oilfields of the WSSB are found in sandstone reservoirs, and this paper describes their petrography and mineralogy, emphasizing on the nature and origin of the clay fraction (<2 µm). Each section was characterized by granulometry and mineral composition using optical microscopy, X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. The uppermost Lower Cretaceous sequence, that appears to be related to volcanogenic debris of high iron content, is characterized by abundant chlorite of similarly high iron content. The clay mineralogy of the petroliferous sandstones in the lowermost Jurassic sequence is not so chloritic but is more kaolinitic, a feature believed to be inherited from weathering of lateritic type soil profiles in the source area, as well as post-sedimentary authigenic conversion of feldspars.

Interpretation of electrical logging data from the Hettangian-Aalenian terrigenous reservoirs in the Southeast of Western Siberia

In the southeast of Western Siberia, the most studied are the Upper Jurassic deposits, most of the oil and gas fields being confined to them. However, the probability of discovering new hydrocarbon deposits in the Upper Jurassic horizons is extremely small. Therefore, of great importance is finding new hydrocarbon deposits in less studied deep-lying complexes. The article considers the development of a criterion for determining the saturation type of the terrigenous reservoirs in the Hettangian-Aalenian deposits in the southeast of the West Siberian sedimentary basin. We use the example of the Ust-Tym megadepression, a large depression located in the central part of the Tomsk region. The Lower and Middle Jurassic sections are represented by the Urman and Togur formations, Salat formation (Peshkov formation is its isochronous analogue) and Tyumen formation, and characterized by the alternation of predominantly sandy (potential reservoirs) and argillaceous-carbonaceous (seals) sequences. In the studied interval, tests were carried out in just a few wells, for which reason the identification of deposits and promising objects is complicated. Determining the type of reservoir saturation will significantly improve the assessment of oil and gas potential. As a result of interpreting lateral logging sounding data, the geoelectric parameters of the invasion zone and undisturbed formation were reconstructed for the Lower Jurassic and Aalenian deposits. Based on the well logging data interpretation by means of numerical inversion, we obtained the criterion for the saturation type of the reservoirs (Ju11-17) in the Hettangian-Aalenian complex. The boundary resistivity values for the oil-saturated reservoirs vary from 8 to 20 ohm∙m, while for the water-saturated ones they do not exceed 5 ohm∙m.

Paleogeography of the West Siberian Sedimentary Basin in the Late Bajocian–Bathonian

Abstract —The paper presents results of regional paleogeographic reconstructions of the West Siberian sedimentary basin in the Late Bajocian–Bathonian. Regional paleogeographic maps of the Yu4, Yu3 and upper part of the Yu2 reservoir units were constructed and described for the first time ever. The implemented approach provided insights into the evolution of paleolandscapes and highlighted the deposition features of the Upper Tyumen Subformation and Malyshev Formation in the different parts of the West Siberian basin. The compilation of paleogeographic maps was based on the electrofacies analysis performed for individual parts of the Malyshev stratigraphic horizon, with regard to the core description materials, paleontological, sedimentological, geochemical data and other. The paleogeographic control of the reservoir’s formation in the Bathonian regional reservoir is discussed.

Modeling the hydrothermal impact on the Jurassic deposits of the West Siberian sedimentary basin (series with H2O and H2O2)

The results of hydrothermal modeling of the formation of epigenetic mineral associations and secondary reservoirs in various types of sedimentary rocks of the Jurassic age in Western Siberia in the H2O-H2O2 system are considered. The experiments were carried out at a temperature of 390°C, a pressure of 70 MPa and H2O2 concentrations varying from 0 to 37.5%. The duration of the experiments was 10 days. In all experiments, a pyrite mixture was added as a buffer. It was found that in experiments in which there was no H2O2, that is, the hydrothermal fluid consisted only of water, there was an intense formation of bitumen and volatile components from the organic matter present in the initial samples. The process of generation of bitumen and volatile components was accompanied by fluid fracturing of rocks and the formation of secondary porosity. Under these conditions, carbonates (calcite, siderite), plagioclases, and kaolinite turned out to be unstable. On the contrary, the formation of hydrothermal ferruginous chlorite was noted. Dissolution of unstable mineral phases by hydrothermal fluid led to the formation of additional secondary porosity. As the concentration of H2O2 and, accordingly, oxygen in the composition of the hydrothermal fluid increased, more and more complete oxidation of the organic matter present in the composition of the sediments was noted until its complete disappearance. With an increase in the oxygen concentration in the composition of the hydrothermal fluid, the appearance of first magnetite and then hematite, native sulfur, and anhydrite was observed. Under hydrothermal conditions with a maximum oxygen concentration, the formation of kaolinite and various sulfates in addition to anhydrite, represented by millosevichite, alum, as well as phases with the participation of elements that make up autoclaves, nickel and chromium sulfates, was noted. Intensive silicification of the sample surface is noted, as well as the constant presence of amorphous silica, which, along with various sulfates, is a quenching phase. These mineral phases are separated from the supersaturated hydrothermal fluid due to its rapid cooling and do not have time to form well-faceted crystals, but are present in the form of loose microporous aggregates. Along with kaolinite, the formation of hydrothermal film illite is noted. The results obtained indicate that the presence of bitumen in the Jurassic sediments is an important exploratory feature, indicating that in this place they were subjected to hydrothermal action, which means, firstly, secondary reservoirs with high filtration and capacity properties were formed, and second, there was an intensive generation of hydrocarbons and, as a consequence, the formation of hydrocarbon deposits.

МИНЕРАЛОГИЯ, ГЕОХИМИЯ И ПРИРОДА СВЕЧЕНИЯ ЛЮМИНЕСЦИРУЮЩИХ ПРОСЛОЕВ БАЖЕНОВСКОЙ СВИТЫ ЗАПАДНО-СИБИРСКОГО ОСАДОЧНОГО БАССЕЙНА

Актуальность. Изучение минералого-геохимических особенностей люминесцирующих прослоев, выделенных в отложениях баженовской свиты на территории Западно-Сибирского осадочного бассейна (Томской области и сопредельных регионов), позволит уточнить их минеральный состав и природу образования, а также оценить возможность их использования как дополнительных региональных реперов для восстановления палеогеографической истории формирования свиты. Цель: изучить минералогические и геохимические особенности и определить природу образования люминесцирующих прослоев в отложениях баженовской свиты. Объекты: осадочные породы, люминесцирующие прослои и вмещающие отложения баженовской свиты. Методы: рентгеновская дифрактометрия, петрографический анализ, сканирующая электронная микроскопия, масс-спектрометрия с индуктивно связанной плазмой, атомно-эмиссионная спектрометрия с индуктивно связанной плазмой, инструментальный нейтронно-активационный анализ, рентгенолюминесценция. Результаты. На территории распространения баженовской свиты в центральной и юго-восточной части Западно-Сибирского осадочного бассейна обнаружены люминесцирующие в ультрафиолетовом освещении прослои мощностью от 2 мм до 15 см. Изучение минерального состава позволило разделить выделенные прослои на две группы по основной минеральной фазе. Изучение прослоев I группы показало, что они сложены в основном глинистыми минералами с примесью обломочного алевритового материала. Основными глинистыми минералам в них являются каолинит и смешаннослойные образования ряда иллит–смектит. Ко II группе отнесены прослои с преимущественно кремнистым (кварцевым) составом. При анализе данных химического состава выявлено, что изучаемые прослои имеют пониженные содержания элементов (Co, Ni, Cu, Zn, Mo и др.) по сравнению с «обычными» породами баженовской свиты в связи с низким содержанием захороненного органического вещества, с которым традиционно связывается накопление некоторых элементов. Отмечены повышенные концентрации тория в образцах изучаемых прослоев. Проведенные исследования выявили признаки присутствия вулканогенного материала. Предполагается, что выделенные прослои имеют вулканическое происхождение и образовались в результате диа- и катагенетического преобразования вулканокластического материала туфовых осадков в присутствии большого количества органического вещества.

Hydrogeochemistry of Pre-Jurassic Aquifers in West Siberia

Abstract ––For the first time in the last 35 years, hydrogeochemical data on pre-Jurassic complexes in West Siberia have been generalized. Groundwater and brines of Cl–Na and Cl–HCO3–Na type with total salinity (TDS) varying from 4 to 330 g/L are found to be widespread in the area under study, with the former type dominating. A detailed analysis of the hydrogeochemical data allowed us to assume the presence of three genetic groups of groundwater and brines in the hydrogeologic section: (1) sedimentogenic, (2) lithogenic (revived) and ancient infiltrogenic, and (3) condensatogenic. An integrated analysis of coefficients rNa/rCl, Ca/Cl, (Br/Cl)·10–3, and (Sr/Cl)·10–3 and integrated index S of brine metamorphization in the Siberian sedimentary basins has corroborated the fact that groundwater and brines in West Siberia are at the initial stage of metamorphization of their chemical composition. Groundwater and brines in the studied Siberian sedimentary basins show an increase in the degree of metamorphization (catagenetic changes) of their chemical composition in transition from the areas of igneous and metamorphic deposits at the base of the Meso–Cenozoic sedimentary cover of the young West Siberian sedimentary basin to the structures of the ancient Siberian Platform, where ultrastrong Ca–Na and Ca chloride brines are widespread.

Lithologic, Geochemical and Geophysical Characteristics of the Boundary Strata of the Bazhenov and Kulomza Horizons (Lower Cretaceous Base) in the Central Regions of the West Siberia

Abstract —The gradual transition of the Bazhenov Formation top into the overlying deposits makes it difficult to establish its upper boundary. The problem is aggravated by the lack of core material when the formation is recognized according to the results of geophysical well studies. A comprehensive analysis of geochemical and lithological data and the results of geophysical well surveys enabled us not only to determine the specific structure of the transitional zone from the Bazhenov Formation top to the rocks of the sub-Achimov member, but also to propose the criteria for delineating the upper boundary in the central regions of the West Siberian sedimentary basin within the Khentei hemianteclise, the South Nadym megamonoclise and the Mansi syneclise. Four members are distinguished in the transitional zone of the studied well sections (from bottom to top), which differ in lithological, geochemical and geophysical characteristics: (I) the “coccolithic” upper part of the Bazhenov Formation; (II) transitional member from the upper part of the Bazhenov Formation to the bottom of the sub-Achimov member; (III) transitional member from the bottom of the sub-Achimov member to its lower part; and (IV) the lower part of the sub-Achimov member. Member II is virtually not distinguished within the Khentei hemianteclise and the South Nadym megamonoclise. Member III contains the boundary between zones with different redox conditions. In case member II is distinguished, the upper boundary of the Bazhenov Formation corresponds to its top. To recognize the Bazhenov Formation top, it is necessary to use the integrated analysis results of the lithological and geochemical studies of the well core, and logging data (gamma-ray logging, neutron gamma-ray logging and its variations, lateral logging, and induction logging) when focusing attention mainly on radioactivity.

A Model of the Geological Structure and the Oil and Gas Prospects of Neocomian (Berriasian–Lower Aptian) Sediments of the West Siberia Arctic Regions and the Kara Sea Shelf

Abstract —The paper presents a model of the geologic structure of Neocomian (Berriasian–lower Aptian) sediments in the Arctic regions of West Siberia and on the shelf of the Kara Sea. The southern part of the Kara Sea is the northern end of the West Siberian sedimentary basin and is identified as the South Kara regional depression of the West Siberian oil and gas province (OGP). Structural and tectonic analysis was performed, and 97 oil- and gas-promising anticlinal objects (structures of ranks III–IV) were identified in the Neocomian megacomplex relief, including 61 on the continent and 36 on the shelf. In the Yamal and Gydan oil and gas areas (OGA), the Neocomian complex of sediments has a structure typical of West Siberia. The megacomplex includes clinoform and shelf complexes. Clinoforms resulted from the ablation of terrigenous material from the eastern and southeastern edges of the plate and are tilted in the northwestern direction; the depocenter within which the eastern and western clinoforms converge is located in the Urals zone, west of the Nurmin megaswell. In the South Kara regional depression, the Berriasian–lower Aptian megacomplex is also represented by clinoform and shelf complexes. On the Kara Sea shelf, Neocomian clinoforms are tilted in the southern, western, and eastern directions; they resulted from the ablation of sediments from the Novaya Zemlya Archipelago and the Siberian Sill. Throughout most of the South Kara regional depression, clinoforms have a typical structure and contain shelf and Achim sandstones that can concentrate significant volumes of hydrocarbons; in the northeast, in the pre-sill zone, clinoform deposits will be represented by poorly sorted “dump” sandstones.

Facies-Stratigraphic Zonation of the Callovian–Kimmeridgian Deposits of the West Siberian Sedimentary Basin

Abstract —We propose a facies-stratigraphic zoning of the Vasyugan and Georgievka horizons in the sedimentary cover of the West Siberian Basin, including the southern part of the Kara Sea. Based on the typification of well sections and taking into account the paleogeography of the Callovian–Kimmeridgian deposits, we have recognized 12 regions with different structures of the Vasyugan and Georgievka horizons. The Purpei–Vasyugan area is divided into three subareas according to the structure of the Vasyugan Formation including the petroliferous horizon Yu1. Transition zones have been recognized between the Vasyugan Formation and the bordering Abalak, Tatar, and Naunak formations along the western, southern, and eastern boundaries of the area, respectively. The results of zoning of the Callovian–Kimmeridgian deposits, including the petroliferous horizon Yu1, can be used on planning of exploration work, for selecting standard facies models, and for predicting the petrophysical properties of a reservoir.

ЭВОЛЮЦИЯ ГИДРОГЕОХИМИЧЕСКОГО ПОЛЯ СЕВЕРНЫХ И АРКТИЧЕСКИХ РАЙОНОВ ЗАПАДНО-СИБИРСКОГО ОСАДОЧНОГО БАССЕЙНА В МЕЗОЗОЕ

Актуальность исследования состоит в выявлении фундаментальной роли палеогидрогеологических факторов в эволюции гидрогеохимического поля северных и арктических районов Западно-Сибирского осадочного бассейна в мезозойскую эру. Впервые предложен механизм, объясняющий их вклад в формирование гидрогеохимических аномалий в оксфордском резервуаре (верхнеюрском водоносном комплексе) изучаемого региона, где широко развита гидрогеохимическая инверсия. Цель: выявить особенности состава сингенетичных вод, захораниваемых одновременно с осадком на элизионных и инфильтрационных этапах развития осадочного бассейна на основе установленной цикличности гидрогеологической истории северных и арктических районов Западно-Сибирского осадочного бассейна; выполнить сравнительных анализ состава современных и сингенетичных вод и установить природу гидрогеохимических аномалий. Методы. Использованы методические приемы А.А. Карцева, С.Б. Вагина, Е.А. Баскова и других исследователей по палеогидрогеологическим реконструкциям осадочных бассейнов, выполнена периодизация гидрогеологической истории с выделением основных гидрогеологических циклов и инфильтрационных и элизионных этапов. На основе методики восстановления солевого состава вод древних морских и озерно-аллювиальных бассейнов, палеогеографических карт на юрский и меловой периоды, составленных сотрудниками ИНГГ СО РАН, информационного банка данных лаборатории гидрогеологии осадочных бассейнов Сибири ИНГГ СО РАН по арктическим районам Западно-Сибирского осадочного бассейна проведены палеогидрогеохимические реконструкции юрско-мелового разреза. Результаты. Приводятся результаты палеогидрогеологических реконструкций северных и арктических районов Западно-Сибирского осадочного бассейна. Установлено, что в гидрогеологическом разрезе исследуемого региона доминируют седиментогенные воды, в некоторых случаях разбавленные инфильтрогенными, проникшими при регрессии морского бассейна. Сравнительный анализ захороненных сингенетичных вод оксфордского бассейна и данных по современной гидрогеохимии подземных вод выявил ряд отрицательных и положительных аномалий. Отрицательные аномалии закономерно трассируют границу глинизации оксфордского регионального резервуара и связаны с развитием процессов элизионного водообмена. Геостатическая (литостатическая) водонапорная система на глубинах 2‒2,5 км переходит в термодегидратационную, что сопровождается аномально высокими пластовыми давлениями и появлением в водонапорной системе пресных химически-связанных вод. Большинство положительных аномалий приурочены к структурам Южно-Надымской и Предъенисейской мегамоноклиз, где широко проявлены процессы вертикальной разгрузки подземных вод нижне-среднеюрского и палеозойского водоносных комплексов в зонах тектонических нарушений. Системе «вода–порода–газ–органическое вещество» принадлежит ключевая роль в процессах формирования химического состава подземных вод нефтегазоносных отложений.

Geochemistry and catagenetic transformation of kerogen from the bazhenov horizon

A representative suite of 276 samples was used to study the isotopic and element geochemistry of kerogens from the Bazhenov horizon (Bazhenov Formation and its time equivalents) of the West Siberian sedimentary basin and to construct maps reflecting changes in the elemental composition of kerogen. The elemental composition of kerogen was used to determine the types of organic matter (H and C contents), the initial components of the living matter, the sources of kerogen (H and N contents), diagenetic history of organic matter (S content), the level of catagenetic transformation (C and O contents).&#x0D; Kerogen from the central, western and southern regions of the West Siberian basin toward the boundary of the Bazhenov horizon pinch-out shows strong enrichment in hydrogen (up to 8–9%) and 12С (δ13С‰ from -35 to -29), suggesting its derivation from the polymer lipids of aquatic origin. Kerogen from the Bazhenov horizon (catagenetic grade MC1) in the northeast of the basin contains much lower hydrogen concentrations (2–4%). A map of organic matter types in the Bazhenov horizon was constructed.

Role of elision water exchange in formation of the Yamalo-Kara depression hydrodynamic field

The unique material has been compiled on the hydrodynamics of oil and gas deposits of the Yamalo-Kara Depression for the first time in the last 30 years. The main feature of the region is the wide development of abnormally high formation pressures (Ka to 2.21) in both Jurassic and Lower Cretaceous horizons. Studying the filtration-capacitive properties and hydrodynamic characteristics of the Jurassic-Cretaceous reservoirs allows to established the predominate role of the elision water exchange in the formation of the modern hydrodynamic structure. At the depth of about 2–2.5 km elisional lithostatic system begins to acquire the features of elisional thermo-dehydration system. The extensive zones of piezomaxima (Bolshekhetskaya and Karskaya megasyneclise) at the present stage of development of the water-pressure basin system became internal areas of water pressure (supply) with a maximum degree of hydrogeological closeness. The vast zones of piezomaxima (the Bolshekhetskaya and Karskaya megasyneclises) became the inner regions of water pressuring (feeding) with the maximal degree of hydrogeological closeness of the interior at the current stage of the development of the water-pressure system in the basin. The areas of piezominima extending along the main sites of oil and gas generation are related to the largest zones of oil and gas accumulation (Vankoro-Suzunskaya, Bovanenkovskaya, Urengoyskaya and others). Currently, two types of natural water-pressure systems has been established in the region under investigation: elision in the inner regions (dominating within the Yamalo-Kara depression) and infiltration — in the basin margins of the West Siberian sedimentary basin.

Role of Elisional Water Exchange in the Hydrodynamic Field Formation in the Yamal–Kara Depression

Unique material pertaining to the hydrodynamics of petroliferous rocks in the Yamal–Kara Depression has been summarized for the first time in the last 30 years. The region is distinguished by a wide development of anomalous high formation pressure (Ca up to 2.21) in both Jurassic and Lower Cretaceous rocks. Results of the study of filtration-capacity properties and hydrodynamic characteristics of reservoir rocks in the Jurassic–Cretaceous section suggest a dominant role of the elisional water exchange in the formation of modern structure of the hydrodynamic field. Elisional lithostatic system located at a depth of about 2–2.5 km begins to acquire features of elisional thermodehydration. At the current development stage of the basinal aquifer system, spacious piezomaximum zones (Bol’shaya Kheta and Kara megasyneclises) became internal water load (supply) zones with the maximal hydrogeological closedness in the Earth’s interior. Piezominimum zones extending along the main centers of oil-and-gas generation match the largest oil-and-gas fields (Vankor–Suzun, Bovanenkovo, Urengoi, and others). At present, we can define in the study region two types of natural aquifer systems: (i) elisional type prevailing in the internal sectors (e.g., Yamal–Kara Depression); (ii) infiltrational type prevailing in the external (marginal) sectors (West Siberian sedimentary basin).

Geothermal Conditions and Petroleum Potential of the Tyumen and Malyshevka Formations of the West Siberian Basin

Abstract —The paper considers present-day rock temperature distribution in the top of the Tyumen and Malyshevka Formations throughout the West Siberian sedimentary basin. A temperature variations map based on earlier and newly obtained data has been compiled for regional hydrocarbon reservoir Yu2. A forecast of the temperature variations in the Malyshevka Formation top has been made for the Arctic regions that have not been well studied with deep drilling. Analysis of hydrocarbon pools distribution within the Bathonian reservoir is presented.

Закономерности размещения залежей углеводородов в берриас-нижнеаптских отложениях северных районов Западно-Сибирского осадочного бассейна

Закономерности размещения залежей углеводородов в берриас-нижнеаптских отложениях северных районов Западно-Сибирского осадочного бассейна