Siberian Basin Research Articles

Asian Paleocene charophyte records demonstrate Eocene dispersals from Asia to Europe

AbstractA latest Paleocene charophyte flora collected from the South Gobi area in the Junggar Basin, western China, includes the geographically widespread taxa Peckichara torulosa var. varians (Dollfus and Fritel, 1919) Sanjuan, Vicente, and Eaton, 2020, Lychnothmanus vectensis (Groves, 1926) Soulié-Märsche, 1989, and Gyrogona lemani capitata Grambast and Grambast-Fessard, 1981. Lychnothmanus vectensis (as Lychnothmanus aff. L. vectensis) is known from the Cretaceous–Paleocene transition in eastern China and the latest Paleocene in western China, with likely additional records from the United States (Utah). The earliest European records of L. vectensis are from the late Eocene to early Oligocene in Spain, France, and England. Similarly, the oldest record of G. lemani capitata is from the latest Paleocene in the South Gobi area, with younger records from the middle Eocene of France. These latest Paleocene gyrogonite assemblages demonstrate the origin of these charophyte lineages in Asia. The dispersal of these charophytes from Asia to Europe in the middle to late Eocene appears to have occurred before the retreat of the Turgai Strait in both the Tarim area and the Siberian Basin by the end of the late Eocene and before the “Grande Coupure” in Europe and the Mongolian Remodelling in Asia during the Eocene–Oligocene transition. We hypothesize that waterbirds may have facilitated this intercontinental dispersal, and that idea is supported by the shared occurrence of avian groups in Central Asia and Europe in the middle and late Eocene.

ГЕОЛОГИЧЕСКОЕ СТРОЕНИЕ ДОЮРСКОГО ОСНОВАНИЯ ЦЕНТРАЛЬНОЙ ЧАСТИ КРАСНОЛЕНИНСКОГО СВОДА В СВЕТЕ НОВЫХ ГЕОЛОГО-ГЕОФИЗИЧЕСКИХ ДАННЫХ

The article reviews features of the pre-Jurassic geological structure of the Krasnoleninsky Swell, located on the western edge of the West Siberian petroleum basin. New geological and geophysical materials are presented enabling significant clarifification of the relationships pattern between Precambrian, Paleozoic and Triassic formation complexes. The stratification of the pre-Jurassic section is based on previously known age determinations and datings made in recent years by high-precision methods. The analysis of mode of occurrence of Pre-Jurassic rock complexes is based on the interpretation of seismic materials and gravity and magnetic data. The proposed model of the Krasnoleninsky Swell pre-Jurassic basement is characterized by the significantly reduced volume of pre-Cambrian formations due to the expansion of the Paleozoic complexes area, local Paleozoic depressions at the base of the Yem-Yegovskaya and Kamennaya peaks and linear zones of development of Triassic terrigenous-volcanogenic rocks on the Talinskaya Terrace and in the Palyanovsky trough have been identified. The conclusion is made about the long and complex history of the basement structure formation in the zone of collision junction of divergent Ural and Central-West Siberian folded systems.

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.

SOME FEATURES OF CURRENT TECHNOGENIC MOVEMENTS OF THE EARTH’S CRUST

We describe the history of studying the current crustal movements by various methods and discuss technogenic effects recorded at large water-reservoir zones and mineral deposits in Siberia. Initially, classical surveying techniques aimed to obtain high-accuracy ground-based measurements of height, tilt and direction. Modern geodesy techniques and methods for measuring absolute gravity are now available to investigate displacement, deformation, tilt and other phenomena taking place on the Earth’s surface. These methods are used to estimate kinematic parameters of the crust areas (e.g. rates of subsidence and horizontal movements) and to monitor fluid motions in mineral deposits. Such data are critical for ensuring a proper management of the mineral deposits. In this article, we analyse technogenic processes observed in the Ust Balyk oil-gas field, the Zapolyarny gas deposit, the water-reservoir zone at the Sayano-Shushenskaya hydroelectric power station (SSHPS) on the Yenisei river, and large open-pit mines in the Kuzbass basin. Our analysis is based on surface displacement rates estimated from the data collected in different periods of observations at large man-made facilities. In the study of the hydro technical objects, we estimated the displacement rates at 5.0 mm per year. In the northern areas of the West Siberian petroleum basin, subsidence rates amounted to 20–25 mm per year in the early 2000s. These estimates were supported by the high-accuracy gravity measurements showing an increase up to 6–7 microGal per year in the oil-gas field development areas. We assess a possibility of triggering effects related to weak seismicity due to a high stress accumulation rate (1 KPa per hour) in the SSHPS area. A connection between earth tides and catastrophic events, such as gas emissions in high amounts on mining sites, is discussed. Having analysed the surface monitoring records taken in South Primorye in September 2017, we conclude that underground nuclear explosions in North Korea in this period did not cause any significant displacement of the surface in this most southerly region of the Russian Far East territories.

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.

Geochemical features of the organic matter from Jurassic sediments of the Nadym‑Taz interfluve

This paper deals with the evaluation of oil-generation potential derived from the geochemical data on deep-buried Jurassic sedimentary rocks of the Nadym-Taz interfluve being part of the West Siberian petroleum basin (PB). The study provides analysis of samples from ultra-deep and deep wells that penetrated the Mesozoic-Cenozoic sedimentary cover in the north of the central part of PB (En-Yakhinsky, Evo-Yakhinsky, Yarudeysky, Tyumensky areas, etc.). The research focuses on the insoluble organic matter (OM) from Upper, Middle and Lower Jurassic sediments (54 samples). A comprehensive study of the kerogen by elemental, isotope analyses and pyrolysis Rock-Eval allowed obtaining the data critical for determining the genetic type of OM, its thermal maturity and residual petroleum generating potential. Using the Surfer and Corel Draw software, schematic maps and diagrams of variations in the most informative (i.e. area-specific and depth-dependent) geochemical parameters of the kerogen on the studied area and also down the section (from the Upper to the Lower Jurassic) were constructed and analyzed. The obtained geochemical data indicate that in the Jurassic sediments of the Nadym-Tazovsky interfluve, the highest OM generation potential is found in the Bazhenov horizon, as well as in individual members of the Malyshevsky, Leontievsky, Sharapovsky and Kiterbyutsky horizons. Based upon the level of OM maturity in the Upper and Middle Jurassic sediments, deposits of mainly oil and fat gases could be preserved, and in the Lower Jurassic – deposits of fat and dry gases.

Siberian Coal Exports: Geographic Directions and Scope

ABSTRACT This article analyzes the scope of Siberian coal exports and indicates the countries (both eastern and western) that import this coal. It also sets out the history of the shipment of Siberian coals outside the region’s borders and reviews existing and potential directions for the coal exports of various Siberian basins and fields. In turn, it determines the volume of coal exports for each Siberian field and export direction, analyzes the transportation infrastructure used by Russia to ship coal, and studies the problems and limiting factors affecting the export of coal from Siberia. These problems and factors are connected, first and foremost, with railroads and cargo ports. Furthermore, the article studies the opportunity for overcoming these factors by reconstructing old railroad branches, constructing new railroad branches, using alternative means of shipping coal products, and increasing processing depth. Finally, it briefly presents the prospects for Siberian coal exports.

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.

Геологическое строение и сейсмогеологическая характеристика континентальной окраины Сибирской платформы и шельфа моря Лаптевых

The work is devoted to the analysis of the geological structure of the northern continental margin of the Siberian Platform and the western part of the Laptev Sea. In terms petroleum geological zoning, the study area covers the Anabar-Khatanga and Lena-Anabar petroleum bearing areas of the Lena-Tunguska petroleum province and the West Laptev Sea promising petroleum province. Seismogeological models of sedimentary stratum on the continent and in the water area are considered; the conclusion was made that the Northern Siberian and Laptev Sea basins are separated by a large basement high that extends from the Taimyr Peninsula along the coastline to the Lena River issue. A complex analysis of geological and geophysical data made it possible to conclude that the most probable model is that the western part of the Laptev Sea is a continuation of the Siberian Platform with an Archaean-Proterozoic basement and an Upper Proterozoic-Phanerozoic sedimentary cover.

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.

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

Литолого-палеогеографические реконструкции юрского периода севера Западно-Сибирского осадочного бассейна

Литолого-палеогеографические реконструкции юрского периода севера Западно-Сибирского осадочного бассейна

Sedimentation Model of Rocks of the Pokur Formation: Basis for the Prediction of Filtration-Volumetric Characteristics (Upper Cretaceous, West Siberia)

The HC-rich Upper Cretaceous rocks in the West Siberian petroliferous basin comprise genetically heterogeneous sediments, resulting in the specificity of morphology, structure, and properties of natural reservoirs therein. One of the possible techniques for more reliable predictions of reservoir rock characteristics is the utilization of results of sedimentation modeling based on the complex interpretation of borehole and seismic data. The paper presents an example of the realization of such approach for refining the structure of oil-and-gas pools in the Pokur Formation of the Russko-Chasel megaswell.

Основные черты геологического строения приграничных толщ юры и мела в приуральской части Западно-Сибирского осадочного бассейна

Основные черты геологического строения приграничных толщ юры и мела в приуральской части Западно-Сибирского осадочного бассейна

TEMPERATURE IN THE DEPOSITS OF MALYSHEV HORIZON OF WEST SIBERIAN SEDIMENTARY BASIN

The article describes the recent distribution of temperatures of rocks in the roof of Tyumen and Malyshev suites for the whole territory of the West Siberian sedimentary basin. A map of temperature changes in the regional oil and gas bearing horizon U2 was built. The prognosis of the temperatures distribution in the roof of Malyshev suite on the understudied by deep drilling in Arctic areas is made. The analysis of placement of the deposits in the Bath with different phase state of the hydrocarbons is presented.

The discovery of Eifelian ammonoids in the Central Kyzylkum Desert (Aristantau Mountains, Uzbekistan)

Eifelian ammonoids are described for the first time from the Central Kyzylkum Desert (Uzbekistan, Navoiy Region, Aristantau Mountains). The ammonoid assemblage includes the typical Eifelian genera Fidelites, Subanarcestes (a new species S. aristanensis Nikolaeva sp. nov. is described), and Cabrieroceras, found in association with brachiopods, conodonts, and dacryoconarids. The ammonoid assemblage is similar to that from the Chotec beds of Barrandien and their equivalents in the Urals, Salair, Germany, and Morocco (Subanarcestes macrocephalus Zone), suggesting a connection between the Eifelian Kyzylkum Basin, which was part of the Turkestan Paleoocean, and European, North African, Siberian, and Uralian basins. The ammonoids studied are not associated with black shale and apparently existed in normal marine environments.

Formation conditions of the Middle Jurassic sandy reservoirs of the Tazovskii deposit, West Siberian petroleum basin

The exploration prospects of the deep Middle Jurassic rocks of the Tazovskii deposit are related to the specific lithological-mineralogical features of reservoirs, which are the major reserve of the region. One of the topical exploration problems is the determination of the formation conditions, which will allow the determination of the prospects of the possible petroleum potential, both of this deposit and the northern part of the West Siberian petroleum basin.

River-gulf system—the major location of marine source rock formation

Petroleum was generated from sedimentary rocks. The world’s oldest oil source rock so far was found in Proterozoic rocks. Since then, 73% to 81% of the earth’s surface has been covered with sedimentary rocks. However, only quite a limited area is rich in oil and gas. It is found that source rocks have controlled oil and gas distribution, and they are mainly formed in two systems: (1) river-lake systems and (2) river-gulf systems. Phytoplankton is an important source of kerogen, the blooming of which is strongly dependent on nutrients. Rivers are the major nutrient provider for basins. Rivers around lakes and an undercompensation (where the sedimentation rate is less than the rate of basin subsidence) environment provide favorable conditions for phytoplankton blooming in lakes. Gulfs are usually located at the estuary of big rivers, characterized by restricted current circulation and exchange with the open sea, which benefit maintaining the nutrient density, phytoplankton levels and organic matter preservation. The river-gulf system is the most favorable place for marine source rock development. Most of the world famous marine petroleum-rich provinces are developed from river-gulf systems in geological history, such as the Persian Gulf Basin, Siberian Basin, Caspian Basin, North Sea, Sirte Basin, Nigerian Basin, Kwanza Basin, Gulf of Mexico, Maracaibo Basin and the Eastern Venezuelan Basin.

Genetic oil types in the southeast of the West Siberian Oil and Gas Basin

The hydrocarbon compositions of oils sampled from collectors of Paleozoic and Jurassic ages in the southeast of the West Siberian Oil and Gas Basin are considered in this work. Based on the interpretation of the distribution of the molecular parameters, the studied samples were divided into four genetic groups with similar coefficient values. Analysis of the hydrocarbon distribution allowed us to identify the type of organic matter, the source for oil formation and the conditions of its accumulation, and the conditions of early diagenesis. In addition, an attempt to determine the ages of the source rocks was made.

The Bazhenovo formation as a source of economic oils and rich gases in the Tithonian-Neocomian section of the South Kara Region

The main gas reservoir in the South Kara region that comprises Arctic areas of the West Siberia petroliferous basin and adjacent shelf is represented by the Aptian-Cenomanian productive sequence, which encloses unique and large gas and gas condensate fields discovered at depths up to 2.5 km: Urengoiskoe, Yamburgskoe, Medvezh'e, Zapolyarnoe, Novopor� tovskoe, Rusanovskoe, Leningradskoe, and others. In recent decades, large fields were discovered in the same sequence in the Ob and Taz estuaries region: Kamennomysskoemore, SeveroKamenomysskoe, Chugor'yakhinskoe, and others. At the same time, resources of cheap dry gas in easily accessible accumu� lations are not inexhaustible, and in the near future, mankind should purposefully develop deeper forma� tions, which contain, in the opinion of many research� ers, accumulations of rich gas and gas condensate with potential fringes of light oils. In the context of this problem, of interest are the results of the geochemical analysis of the Bazhenovo Formation (Tithonian-lower Berriasian), which is characterized by very high concentrations of plankto� nogenic organic matter and represents a main genera� tor of oils in the central and western parts of the West Siberian petroliferous basin. The unique enrichment of this unit with organic matter should also be charac� teristic of high latitude areas, since similar highcar� bonaceous sediments associated with frequently global anoxic events were deposited in the terminal Late Jurassic epoch through many petroliferous basins (North Sea, West Norwegian, Barents Sea, West Sibe� rian, Northern slope of Alaska, Mackenzie, Sverdrup, Jenna D'Arcy), where similar sequences became sources of the economic oil potential. The Bazhenovo Formation is composed of carbon� ate-siliceous-clayey bituminous sediments with high concentrations of planktonogenic organic matter (average Corg contents 5.1% and up to 30% in some layers) (1). By analogy with domanikites, these sedi� ments are called bazhenovites. They are distributed practically throughout the entire basin, where average Corg and bitumoid concentrations increase from 1 to 11% and from 0.3 to >1.0%, respectively, from its periphery toward the inner deepwater parts. The comparison of the lithological-mineralogical characteristics of rocks and the concentrations and composition of enclosed organic matter with the data obtained by the standard and radioactive logging (SL and GL) revealed certain correlations between terrig� enous, biogenic-terrigenous, and biogenic compo� nents of the Bazhenovo Formation, on the one hand, and the SL and GL values, on the other (2). The defined correlation between these parameters served as a basis for classification of bazhenovite sections and their largescale mapping. The sections with members of highresistance siliceous, carbonate, and siliceous- carbonate sapropelic-clayey rocks confined to depressions and slopes of uplifts are considered to be most favorable for the formation of oil pools. In such sections, organic matter is almost entirely represented by colloalgenite and contains 7.0-8.5% of hydrogen, while microcavities in rocks are frequently filled with oil. Perrozio and Predtechenskii (2) proposed in 1985 the notion "radiolarian paleoabundance," which des� ignates the sum of their visible remains concentrated in the form of small lenses and laminae or present as single skeletons as well as residual cavities through the whole rock volume after their dissolution. It was estab� lished that the radiolarian paleoabundance of