A model of the geological structure was constructed and the oil and gas potential prospects of the Yenisei-Khatanga regional trough were assessed. Construction of seismogeological sections, structural and tectonic maps, structural and tectonic analysis was carried out. It was concluded that the Neocomian clinoform complex, which contains about 90 % of oil, gas and condensate reserves in this region, is of the greatest interest in the study area in terms of searching for large oil accumulations. It should be expected that significant oil reservoirs localized in the Berriasian–Valanginian sand formations will be controlled by complex structural-lithological and lithological non-anticlinal traps.

The latest geological and geophysical information on the Zeya-Bureya sedimentary basin (Russia, Far East) is summarized. Based on drilling data from corehole and deep wells and 2D and 3D CDPM seismic data, taking into account the integrated interpretation of gravity and magnetic survey data and geological survey materials, a map was compiled for the surface of the pre-Mesozoic basement of the sedimentary basin, as well as structural maps for the top of the Cretaceous formations. The maps reflect a series of rift grabens and uplifts identified by the authors on seismic time sections during their reinterpretation. The method of compiling maps is given. A geological map of sediments overlying the pre-Mesozoic basement of the Zeya-Bureya sedimentary basin and a tectonic map of the sedimentary cover were compiled. During tectonic zoning of the sedimentary cover, the classification of tectonic elements was adopted that is widely used in the tectonic zoning of oil and gas regions, proposed by V.D. Nalivkin and updated at the Trofimuk Institute of Oil and Gas Geology and Geophysics, Siberian Branch, Russian Academy of Sciences (INGG SB RAS). As a result of tectonic zoning in the basin, the Inner Region and the Outer Belt were identified, and the tectonic elements complicating them were characterized. A characteristic feature of the Outer Belt is the presence of large intermediate structures: monoclines and mega- and mesomonoclines. Conversely, the Inner region of the basin is characterized by the presence of a large negative structure, complicated by smaller positive and negative elements. The main stages of the formation and development of the sedimentary cover of the Zeya-Bureya sedimentary basin are identified and described: rifting, early syneclise, late syneclise, and neotectonic.

This study summarizes the most recent geological and geophysical data on the Zeya-Bureya sedimentary basin (Russian Far East). The stratigraphy of the sedimentary cover is described. A comparative analysis of the Zeya-Bureya sedimentary basin and the Songliao basin (China) to the south of it, which is similar in its tectonic nature, structure and geological history, indicates that the Ekaterinoslavka Formation, occurring at the base of the sedimentary cover and formerly assigned to the Jurassic, is Lower Cretaceous in age. Results of the reinterpretation of the old CDP data (2014–2018) were used to infer the seismostratigraphic characteristics of the section and to identify six geoseismic sequences. The wave pattern of the constructed sections confirms the synrift nature of the grabens at the base of the sedimentary cover of the Zeya-Bureya sedimentary basin. Thickness maps of Cretaceous formations and a tectonic map of the sedimentary cover were compiled from the core and deep drilling data as well as 2D and 3D CDP seismic survey data taking into account the integrated interpretation of gravity, magnetic, and geological survey data. The evolution of the study area is divided into four stages: synrift, early syneclise, late syneclise, and neotectonic.

16 Рис.5. Карты распределения амплитуд сейсмической записи в интервале пласта АчБН16 1 (A) и литофаций (Б) Восточно-Медвежьего участка (Восточно-Медвежья, Южно-Падинская, Нерутинская площади) 1 -скважины, вскрывшие отложения ачимовской толщи или ее заглинизированный аналог

The West Siberian marine basin of the Volgian–initial Berriasian ages is described. It is shown that a marginal filter (according to A.P. Lisitsyn) functioned in the basin. The main mass of terrigenous sediments was deposited within the eastern margin of the sea. The central part of the basin only received a small amount of the terrigenous material. Water area of the West Siberian Sea was 2 mln 530 thou km2; eastern marginal filter, 535 thou km2; and open epicontinental marine basin, 1 mln 994 thou km2. Depth of the Volgian Sea was 500 m. Mass of sediments in the West Siberian Sea by the end of late diagenesis was 228.4 Tt (recalculated to the anhydrous material), with sediments in the eastern marginal filter accounting for 121.7 Tt. Bioproductivity of the Volgian–Berriasian West Siberian Sea was extremely high. The mass of living matter was composed of archaea, bacteria, and protozoan unicellular eucaryotes (organic-walled), as well as organisms with the siliceous (radiolarians) and carbonate skeleton (foraminifers and others). The rock mass formed from sediments of the central deep-water part of the basin at the stage of diagenesis was 106.7 Tt (recalculated to the anhydrous material), including the mass of organic matter (OM) accounting for 15.8 Tt; mineral (siliceous and carbonate) relicts of organisms, 67.8 Tt; and allothigenic components (clay minerals and iron hydroxides), 23.1 Tt. Analysis of the composition of kerogen (polymerlipids) revealed that the amount of OM transported to sediments was 15–20 times higher than the present-day amount in rocks of the Bazhenov Formation. At the stage of early diagenesis, the OM mass in sediments was as high as 235–320 Tt (recalculated to the anhydrous material). The Bazhenov Sea represented a huge natural ecosystem favorable for the generation, reworking, and accumulation of living matter relicts. At the stage of catagenesis, unique oil-and-gas resources were generated from OM masses deposited in this system.

Рассмотрен Западно-Сибирский морской бассейн волжского — начала берриасского веков. Показано, что в бассейне действовал маргинальный фильтр (по А. П. Лисицыну). Основная масса терригенных осадков накопилась в пределах восточной окраины моря. В центральную часть бассейна попадало небольшое количество терригенного материала. Акватория Западно-Сибирского моря имела площадь 2 млн 530 тыс. км2, акватория восточного маргинального фильтра составляла 535 тыс. км2, область открытого эпиконтинентального морского бассейна — 1 млн 994 тыс. км2. Глубина волжского моря достигала 500 м. Масса осадков в Западно-Сибирском море к окончанию стадии позднего диагенеза составляла 228.4 трлн т (в пересчете на безводное вещество), из них осадков в зоне восточного маргинального фильтра — 121.7 трлн т. Биологическая продуктивность волжско-берриасского Западно-Сибирского моря была исключительно высокой. Основную массу живого вещества формировали археи, бактерии и простейшие одноклеточные эукариоты — органостенные, а также организмы с кремнистым (радиолярии) и карбонатным скелетом (фораминиферы и др.). Масса пород, сформировавшихся из осадков центральной глубоководной части бассейна на стадии диагенеза, составляла 106.7 трлн т (в пересчете на безводное вещество), в том числе масса органического вещества (ОВ) — 15.8 трлн т; минеральных (кремниевых и карбонатных) остатков организмов — 67.8 трлн т; аллотигенных компонентов, представленных глинистыми минералами и гидроксидами железа — 23.1 трлн т. Анализ состава керогена (полимерлипиды) показывает, что органического вещества в осадки поступало в 15–20 раз больше, чем содержится в породах баженовской свиты в настоящее время, и на стадии раннего диагенеза масса ОВ в осадках (в пересчете на безводное вещество) составляла 235–320 трлн т. Баженовское море представляло собой гигантскую природную экосистему по генерации, переработке и аккумуляции остатков живого вещества. Из накопленной в пределах этой системы массы ОВ на стадии катагенеза были выработаны уникальные ресурсы нефти и газа.

The type sections of the Bazhenov Horizon and formations recognized within this horizon have been identified based on a comprehensive analysis of paleontological, lithological, geophysical (well-log and CDP seismic data), and geochemical data on the West Siberian Basin. The Bazhenov Horizon was traced throughout the entire West Siberian sedimentary basin. The criteria for the recognition of the top and base of this horizon within the stratigraphic equivalents of the Bazhenov Formation were suggested. The proposed facies-stratigraphic zonation of the Bazhenov Horizon reflects the spatial location of all formations identified within this horizon. As seen on the newly proposed thickness map, the Bazhenov Horizon reaches a thickness of 15-25 m within the Bazhenov and Tutleim Formations, 30-35 m within the Mulym'ya Formation, 30-45 m within the Danilov Formation, 40-65 m within the Mar'yanovka Formation, up to 100 m within the Golchikha Formation, >350 m within the Yanovstan Formation, up to 35 m within the Bagan Formation, and 35-40 m within the Maksimkin Yar Formation. A marginal filter (according to A.P. Lisitzin) has been identified along the East Siberian land. (C) 2018, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

We discuss the geologic structure of the Berriasian-Lower Aptian deposits of the Gydan Peninsula. Eight seismic sequences have been distinguished; most of them are associated with Lower Cretaceous regional clinoforms of West Siberia, their characteristics are given. A correlation of productive beds was based on the stratotype sections of the Yamal and Gydan Peninsulas as well as seismic and well data. A sequence stratigraphic model of the Berriasian-Lower Aptian complex is proposed. (C) 2018, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

Considered questions of structure and formation conditions of the Berrias-Lower Aptian deposits of the Gydan Peninsula of Western Siberia. Their seismogeological characteristics are given. Recognized eight seismic sequences, most of which have a wedge shape and correspond to third-order sequences. The main prospects for the search for hydrocarbon traps are associated with the Achimov petroleum complex, lenticular sandy-aleuritic beds of which have deep-water genesis. Two types of promising zones are identified for the search for lithological traps in the deposits of the Achimov Formation. One of them is associated with depocenters accumulation of clinoforms, the second - with the regional wedging distal Achimov strata in the direction of the Taimyr paleolandmass.

The geological structure and conditions of formation of a Lower Cretaceous clinoform complex in West Siberia are examined based on sequence stratigraphy. The regional Berriasian-Hauterivian clinoforms are interpreted as third-order sequences, and their formation should be considered in terms of the Depositional Sequence III model. Productive beds of both shallow and deep marine as well as continental genesis formed mostly in a regressive basin and belong to the highstand systems tracts. (C) 2018, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

This paper discusses the problems of selection of stratotype sections and correlation of marker beds in the Neocomian productive complex of West Siberia in the context of its clinoform structure. In this paper we present a conceptual sequence stratigraphic model and a correlation chart for beds from different lithofacies regions of the Berriasian-Lower Aptian deposits of West Siberia. (C) 2017, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

This study presents the results of geochemical analysis of organic matter and paleogeographic reconstructions supplemented by data from well log interpretation and cyclostratigraphic analysis for the Vasyugan, Georgiev, and Bazhenov Horizons of the Callovian-Lower Berriasian section in the western part of Yenisei-Khatanga regional trough and adjacent areas of the West Siberian geosyneclise. It was found that each horizon contains zones dominated by terrigenous, mixed, and aquatic organic matter. The distribution of different types of organic matter over the area and throughout the section has been examined. It was shown that the accumulation of aquatic organic matter took place in the deepest parts of the trough during the Callovian-Oxfordian. The area of accumulation of aquatic organic matter expanded considerably and reached its maximum extent within the Bolshaya Kheta megasyneclise during the Kimmeridgian and Early Volgian and in the west Yenisei-Khatanga regional trough during the Volgian and Early Berriasian.

Paleobathymetrical reconstructions were performed for the Volgian-Neocomian basin in northern West Siberia. The proposed technique takes into account a number of factors, such as the rates of basin subsidence and sedimentation, sediment lithification and types of lithology, sea level changes, and isostasy. The role of each factor controlling the depth of the paleobasin is considered. The study reveals several stages of formation of the Neocomian clinoform complex of West Siberia, with different regimes of basin subsidence, sedimentation, and isostatic compensation. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

The study presents a seismic and geological characterization of the Meso-Cenozoic sedimentary cover of the Nadym-Pur interfluve area and discusses the morphology of the Jurassic and Aptian-Albian-Cenomanian sedimentary complexes, formation history of structures, and geologic processes responsible for the formation of Cenomanian gas accumulations. (C) 2016, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.