The influence of trap magmatism on the creation of oil and gas deposits

The need to maintain the level of production and an acceptable cost of developing oil and gas fields forces us to rely primarily on the existing reserve, that is, to maximize the potential of traditional oil and gas production regions and adjacent territories - the marginal zones. At the same time, it is necessary to develop unexplored sedimentary complexes at depths of more than 3-5 km. Against this background, it is necessary to highlight a special phenomenon that increases the oil and gas potential of the subsoil associated with trap magmatism. The insufficient level of knowledge of the subsoil makes it possible to predict the discovery of large oil and gas deposits of the traditional type, which will ensure their high profitabilitye. Keywords: trap magmatism; profitability of oil and gas resources; marginal zones; hornfels; transformation of carbonates; rocks of trap formations; regional seals.

Middle devonian-lower frasnian natural hydrocarbon reservoirs of the Pechora Sea shelf and Timan-Pechora oil and gas province adjacent area

The research is based on the three-layer natural hydrocarbon reservoirs theory, which allocates 3 layers in a natural reservoir – the genuine seal, the productive part and the intermediate layer situated between them - the false seal. The Middle Ordovician-Lower Frasnian terrigenous complex variable in thickness, composition and stratigraphic completeness sub-regional natural reservoir was identified in the northern part of the Timan-Pechora oil and gas province adjacent to the Pechora Sea. It includes several zonal and local natural reservoirs (Middle Ordovician-Lower Devonian, Middle Ordovician-Eiffelian, Zhivetian-Lower Frasnian and others). The distribution areas of these natural reservoirs were extrapolated to the Pechora Sea offshore. The areas with the highest prospects of oil and gas potential of the Pechora Sea offshore were delineated, basing on the Timan-Pechora oil and gas potential analysis. These are the northwest extensions into the Pechora Sea of the Denisov trough, the Kolva megaswell, as well as the Varandei-Adzva structural zone and the Karotaiha depression. Keywords: natural reservoir; genuine seal; false seal; field; pool; hydrocarbons.

Forecast and assessment of hydrocarbon potential of cretaceous and jurassic deposits of the Kara Sea shelf based on the results of geological exploration

According to the oil and geological zoning, the water area of the Kara Sea, including the Ob and Taz Bays, is located on the border of three oil and gas-bearing regions: Yamal, Gydan and Nadym-Purskaya, having different characteristics of oil and gas potential by section and by area. As a result of geological exploration carried out in the water area and on the adjacent land, a wide age range of oil and gas potential was revealed. Seven fields have been discovered in the waters of the Yuzhno-Kara NGO: six gas condensate fields in Cretaceous Cenomanian-Albian deposits and one oil and gas condensate field in Cretaceous and Jurassic deposits. Large gas condensate fields have been explored in the Ob and Taz bays in the Cenomanian-Alb-Apt complex. The water area of the lips is one of the most important areas in terms of the growth of economically viable natural gas resources. According to the research results, it has been established that the UV potential of the Jurassic and Lower Cretaceous complexes of the Ob and Taz Bays is characterized as highly promising. Keywords: Kara Sea; shelf; cretaceous and jurassic deposits.

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.

The oil and gas potential of the north of the Siberian platform and adjacent shelf

The objective of this article is an estimation of the oil and gas potential of the north of the Siberian platform and adjacent shelf. The Siberian platform is characterized by a large concentration of oil and gas resources in the southern and central parts of the platform. The main oil and gas province of the Siberian Platform is the Leno-Tungus oil and gas province. The oil- bearing strata in the Lena-Tungus oil and gas province are confined to the Riphean, Vendian, Lower-Middle Cambrian deposits, in which large oil and gas fields are discovered. In modern contours the Siberian platform in the north and north-west is fringed by the Yenisei-Khatanga regional trough. In the east, the Yenisei-Khatanga regional trough is connected with the Anabar- Lena trough, framing the north-eastern part of the Siberian platform. Analysis of the available geological and geophysical materials shows a fairly high potential of the Anabar-Lena and Yenisei-Khatanga troughs for the discovery of large hydrocarbon fields. The basic understanding of the geologic-tectonic structure and petroleum potential of the northern part of the Siberian Platform and the adjacent shelf of the Arctic zone are currently based on seismic data by the method of the common depth point (CDP), tied to the existing deep search and parametric wells. Representations of the deep structure and oil and gas potential of specific areas, the allocation of targeted promising oil and gas horizons can change dramatically as the depth of seismic acquisition of the method of the common depth point increases and the software for processing and interpreting seismic data is improved. The localized oil and gas resources of the north of the Siberian platform and adjacent shelf are 41017,3, subsequently, 27582,3 - onshore and offshore - 13435 MMT (million tons) of oil equivalent.

Salt structures of the sedimentary cover of the Russian platform as a reflection of possible geodynamically active foci of hydrocarbon generation in the basement (on the example of the south-west of the Orenburg region)

В 2021 году А.А. Драгуновым при помощи системно-геодинамического дешифрирования были выявлены Восточно-Оренбургский и Западно-Оренбургский геодинамически активные очаги генерации углеводородов Оренбургского нефтегазоконденсатного месторождения. Было предположено, что ряд малых залежей юго-запада Оренбургской области также получают от них подпитку. Целью представленной работы являлась попытка проследить вышеуказанные очаги генерации углеводородов в фундаменте и осадочном чехле на основе переинтерпретации временных разрезов региональных сейсмических профилей. Методы работы. Выделение тектонических нарушений проводилось вручную с применением авторских методических приемов приближений и последовательной детализации. После чего выполнялось системное обобщение и анализ полученных результатов в свете перспектив нефтегазоносности юго-запада Оренбургской области. Результаты работы. В результате работ было рассмотрено глубинное строение очагов, отмечены сейсмогеологические особенности их обнаружения. В местах картирования очагов генерации на временных разрезах зафиксированы неотектонические разломы «цветкового» типа, хаотическая вертикально направленная локально усиленная сейсмическая запись под ними ниже отражающего горизонта, отождествляемого с породами фундамента. Прослежена связь глубинных разломов и связанных с ними новейших оперяющих разломов с солянокупольными структурами кунгурского возраста. По результатам комплексного геологического анализа структурных построений выявлена схематическая сеть неотектонических разломов фундамента, судя по которой, Оренбургское нефтегазоконденсатное месторождение и другие, более мелкие месторождения углеводородов и выявленные сейсморазведочными работами структуры юго-запада Оренбургской области имеют закономерное распределение внутри крупной радиально-концентрической структуры диаметром около 180 км. Данная структура, вероятно, представляет собой зону разуплотнения в фундаменте, в пределах которой в осадочном чехле образовались перспективные в плане нефтегазоносности структуры. Уникальное и самое крупное в пределах юго-запада Оренбургской области Оренбургское месторождение находится в центре макроструктуры, являясь, возможно, результатом работы главных очагов генерации УВ в фундаменте. Вдоль радиальных и концентрических разломов сосредоточены более мелкие месторождения углеводородов. Кроме того, Оренбургское месторождение приурочено к зоне наложения двух концентров, что, возможно, является значительным фактором при обнаружении крупных месторождений. В качестве выводов даны рекомендации для дальнейших исследований и поиска возможных геодинамически активных очагов генерации углеводородов в пределах Русской платформы In 2021, A.A. Dragunov, using system-geodynamic decoding, identified the East-Orenburg and West-Orenburg geodynamically active centers of hydrocarbon generation of the Orenburg oil and gas condensate field. It was assumed that a number of small deposits in the south-west of the Orenburg region also receive recharge from them. The aim of the presented work was an attempt to trace the above-mentioned sources of hydrocarbon generation in the foundation and sedimentary cover on the basis of reinterpretation of time sections of regional seismic profiles. Methods. The selection of tectonic disturbances was carried out manually using the author's methodological techniques of approximations and sequential detailing. After that, a systematic generalization and analysis of the results obtained was carried out in the light of the prospects for oil and gas potential of the south-west of the Orenburg region. Results. As a result of the work, the deep structure of the foci was considered, the seismogeological features of their detection were noted. Neotectonic faults of the "flower" type, chaotic vertically directed locally enhanced seismic recording under them below the reflecting horizon identified with the basement rocks were recorded in the places of mapping the generation centers on time sections. The connection of deep faults and the newest feathering faults associated with them with salt-dome structures of the Kungur age is traced. According to the results of a comprehensive geological analysis of structural structures, a schematic network of neotectonic basement faults has been identified, judging by which the Orenburg oil and gas condensate field and other smaller hydrocarbon deposits and the structures identified by seismic surveys in the southwest of the Orenburg region have a regular distribution within a large radial-concentric structure with a diameter of about 180 km. This structure probably represents a zone of decompression in the foundation, within which promising structures in terms of oil and gas potential were formed in the sedimentary cover. The Orenburg deposit, which is unique and the largest within the south-west of the Orenburg Region, is located in the center of the macrostructure, possibly being the result of the work of the main centers of HC generation in the foundation. Smaller hydrocarbon deposits are concentrated along the radial and concentric faults. In addition, the Orenburg field is confined to the zone of overlap of two concenters, which is probably a significant factor in the discovery of large deposits. As conclusions, recommendations are given for further research and search for possible geodynamically active centers of hydrocarbon generation within the Russian platform.

Features of the geological structure, tectonic development and oil and gas potential of the Chezhen depression (Bohai bay basin)

Background. In terms of oil and gas, the territory of the Chezhen depression has been studied insufficiently compared to the neighbouring same-range depressions. These depressions complicate the first-order Jiyang depression, geographically coinciding with the largest Shengli hydrocarbon field. In recent years, much geological and geophysical information about the oil geologyof the Chezhen depression has been accumulated, which allows its prospecting oil and gas potential to be assessed.Aim. To reveal regular features of the geological structure and location of oil deposits in the Chezhen depression in order to support the prospecting and exploration work within the Chezhen block of the Shengli field.Materials and methods. A comprehensive analysis of literature data and collected materials was conducted. A historical and geodynamic study of the evolution of the studied area according to literature data was carried out, along with an analysis of the most recent geological and geophysical information and exploration data based on the materials of the “Shengli AKOO Sinopek” oil company. The analysis was based on the data from 52 drilling wells and the results of seismic surveys performed in the central part of the Chezhen depression.Results. Specific features of the block geological structure of the area under study were established, which formed under the repeated influence of large-scale horizontal tectonic movements occurring at different periods of geological history. The role of the most recent fault system in the modern spatial distribution of oil deposits was determined.Conclusions. Our studies demonstrate a great prospecting potential of the Chezhen depression territory, where the discovery of new industrial oil deposits can be expected.