Search

Large faults mainly predetermined the distribution of hydrocarbon deposits in the Meso-Cenozoic sedimentary cover of Western Siberia and served as migration paths upward the section. The formation of faults had a significant impact on the redistribution of hydrocarbons both between oil and gas bearing formations and by fluid type. In the direction from south to north, the oil and gas bearing level, the number of layers in the field and the number of gas fields is increased. It is proposed to revise the models of tectonically limited layers from the point of view of the theory of the three-layer structure of the reservoir.

The article is devoted to the study of the geological structure of the lower sections of the productive strata of the Lower Pliocene. It consists of an introduction, problem statement, research questions, research methodology, results, conclusion and list of references. The introduction provides basic information about the field under study, its geographical location, the history of geological and geophysical studies, the lithology of the section, the structure of the Kyurovdag fold and the oil and gas potential of the field. It is noted that the oil and gas potential of the Kyurovdag field is associated with the Apsheron stage of the Pleistocene, the Akchagyl stage and the productive stratum (horizons PS01-PS23) of the Neogene, and despite the long development of the field, the lower sections of the productive strata and the underlying deposits have not yet been discovered by deep drilling and due to the complexity of surface , as well as the deep seismogeological structure of these deposits, remained insufficiently studied. 3D seismic surveys have been proposed due to the high level of lateral spurts on the seismic records. The main tasks facing these 3D seismic surveys were to study the geological structure of the Kyurovdag field, to elucidate some of its features hitherto unknown to geologists and geophysicists, as well as to refine the velocity section in order to compile a predictive depth-time dependence for further use. It is indicated that field seismic surveys were carried out by the geophysical company Petroalliance Services Company Limited on the order of Caspian Energy Group. Processing was carried out using the FOCUS processing package version 5.4 from Paradigm geophysical. It is noted that in order to reinterpret the 3D seismic data, CDP-3D materials were obtained for the field and a kinematic analysis was performed for the cubes, which revealed the difference in time shift, frequency spectrum and amplitude range. The cubes were brought to a single form in terms of time, phase and amplitudes, and further kinematic interpretation showed that sufficiently high-quality and conditioned material was obtained for the Kyurovdag area. The studies were carried out using the PANGEA® software package for multi-attribute analysis of geological and geophysical data and standard interpretation. The PETREL.10.2 software package was used for volumetric modeling of the productive formations of the Kurovdag oil field. The objects of study were complex, lithologically and tectonically screened deposits of the productive stratum PS01-PS09 and the Akchagyl stage (AKCH). Deposits of the productive strata belong to the subdivision of the Pliocene division of the Neogene system of the Caspian basin. It is represented by a thick complex of continental and coastal-marine deposits (sands, clays, coarse clastic formations) up to 1600 m thick. It lies unconformably on the deposits of the Pontic stage, overlain transgressively by Akchagyl layers. The Akchagyl Stage is one of the divisions of the Upper Pliocene, the deposits of which are represented by clays, limestones, marls, sandstones, sands, and conglomerates. It was found that the Kurovdag area is characterized by a block structure throughout the studied geological section, and the dimensions of the block also remain almost unchanged, which indicates the correspondence of structural stages and the inheritance of tectonic movements. The development of mud volcanism and diapiric folding, as well as their size, are the main distinguishing features of these maps.

При изучении геологического строения глубокопогруженных нефтегазоперспективных горизонтов и изучении современной геодинамики Терско-Каспийского прогиба (ТКП) весьма актуальным является уточнение пространственного положения существующих и выделение новых разломных структур. Пространственное положение разломов устанавливается по комплексу геолого-геофизических критериев, причем геофизические признаки являются преобладающими. Цель. На основании карты аномалий силы тяжести масштаба 1:200 000 и карты магнитного поля масштабов 1:200 000 и 1:500 000 были созданы цифровые модели гравитационного и магнитного полей и составлена схема аномального гравитационного поля (Δga) западной части ТКП. Электронная база сейсмологической информации была составлена на основе сведений об исторических и инструментальных землетрясениях (1950–2020 гг.), а также макросейсмических данных. Методы работы. Трансформация исходного аномального гравитационного поля выполнена путем расчета вектора горизонтального градиента Wsz и третьей вертикальной производной Wzzz потенциала силы тяжести, с использованием компьютерной программы, реализующей метод F-аппроксимации, основанный на представлении потенциала аномального гравитационного и магнитного полей интегралом Фурье. Для анализа сейсмичности выполнен расчет сейсмической активности А10 по формуле Ю.В. Ризниченко с использованием компьютерной программы, реализующей способ суммирования с постоянной детальностью, основанный на суммировании числа землетрясений всех энергетических классов больше минимального представительного в фиксированной зоне осреднения. Результаты работы и обсуждение. По результатам обработки и интерпретации геофизических данных построена серия тематических карт по территории ТКП: карты вектора горизонтального градиента Wsz и третьей вертикальной производной Wzzz потенциала силы тяжести; карта сейсмической активности А10. На основе анализа полученных данных с привлечением существующей геологической информации уточнено положение известных разломов и выделены новые, по итогам исследований составлена карта разломов западной части ТКП When studying the geological structure of deeply submerged oil and gas promising horizons and studying the modern geodynamics of the Terek-Caspian trough (TCT), it is very important to clarify the spatial position of the existing fault structures and identify new ones. To determine the spatial position of the faults, a set of geological and geophysical criteria is established, with geophysical features prevailing. Aim. Based on the gravity anomaly map of scale 1: 200,000 and magnetic field maps of scales 1: 200,000 and 1: 500,000, digital models of gravitational and magnetic fields were created and a diagram of the anomalous gravitational field (Δga) of the western part of the TCT was drawn. The electronic database of seismological information was compiled on the basis of information about historical and instrumental earthquakes (1950–2020), as well as macroseismic data. Methods. The transformation of the initial anomalous gravitational field is performed by calculating the horizontal gradient vector Wszand the third vertical derivative Wzzzof the gravity potential using a computer program that implements the F-approximation method based on the representation of the potential of the anomalous gravitational and magnetic fields by the Fourier integral. To analyze the seismicity, the seismic activity А10 was calculated according to the formula of Yu.V. Riznichenko using a computer program that implements the summation method with constant detail, based on the summation of the number of earthquakes of all energy classes greater than the minimum representative in a fixed averaging zone. Results and discussion. Based on the results of processing and interpretation of geophysical data, a set of thematic maps was built for the TCT territory. This set includes maps of the horizontal gradient vector Wsz and the third vertical derivative Wzzz of the gravity potential; seismic activity map А10. Based on the analysis of the data obtained with the involvement of existing geological information, the position of the known faults was clarified and new ones were identified, based on the results of the research, a map of the faults for the western part of the TCT was compiled

This article describes the nature of including of Verkhoyansk-Chukotka area Verkhoyansk-Kolyma. Chukotka and South Anyui folded belts. It is shown, that formation these belts is not connected with the impulse of collision of Siberian and Arctic plates. The crumpling rocks of first of them into giant horizontal fold (Kolyma loop) is explained as a drift of Omolonsky massif along the border of Siberian craton. Sigma-form of Chukotka belt is cutting the structures Koluma loop is allow to interpret it as a lateral tectonic flow, which deforms Sigma as a result lock up its heads Anui-Novosibirsk part volcanic covers of Ohotsk-Chukotka belt. These data allow uncovering Verkhoyansk-Chukotka region as region of skirmish of structures of two lateral tectonic flowes of Polar province of Earth, composing on South Anyui-Pekulney transform fault.

Summary Numerous observations on outcrops, as well as theoretical considerations, confirm the effect of first-generation fractures on second-generation fractures. Parameters of fractures of the second generation are associated with a modified stress field due to previously formed fractures. To date, software products have been developed that allow the calculation of changes in the stress field due to previously formed fractures or faults. However, a large number of factors affect the predictive ability: such as the nature of fractures, the accuracy of estimating the parameters of first-generation fractures, the quality of the initial data etc. In this project, it is proposed to assess the possibility of predicting the second generation fracturing from the available data on the first-generation faults. During the study, the relationship between fractures of the first and second generations was confirmed. However, the zone of influence of the preexisting fractures significantly depends on the specific stress ratio in certain periods of time, which not easily could be predicted and is the main sources of the uncertainties. Also, the 3D BEM has some limitations and assumptions. Hence, the actual predictability of the second-generated faults and fractures is low and could be performed in a very limited area.

The purpose of this work is to determine the parameters of fault tectonics by constructing an inversion stresses model with a weak quality of the seismic survey, as well as identification of compression and extension sectors by the structural-geomorphological method (SGM) in subsalt productive sediments. The tasks for achieving the goal of the paper: analysis of the quality of available information about fractures within the studied oil deposit, calculation of the inversion stress model, identification of the compression and extension sectors according to the SGM. Reconstruction of stress fields in conjunction with geomechanical analysis is a tool for studying the patterns of fracture development in rocks and tectonic evolution of the region. Determination of fault parameters and allocation of zones of intensive fracturing allows optimizing trajectories when drilling horizontal and inclined wells, assuming intervals of potential drilling complications, predicting risks during fracturing operations, and qualitatively evaluating the reservoir properties by deformation sectors. As inputs to the calculation of the inversion stress model, disjunctive dislocations that are confidently identified by seismic data and records of an electrical microimager appear. Based on information about the spatial location of the actual cracks and faults, the orientation of the tectonic force contributing to the formation of this fault system is calculated. The result of the construction of the inversion stress model are maps of displacement and deformation fields. Analysis of these maps in zones with different values of displacements and deformations allows to single out low-amplitude disjunctive dislocations, which are ambiguously determined when interpreting seismic survey. The calculation results are calibrated for microimager data, special core studies, drilling data. The initial data for the structural-geomorphological method are topographic maps, space images and digital surface models. As a result of applying the structural-geomorphological method, it is possible to reconstruct the orientation of the axes of compression and stretching of neotectonic stresses in the horizontal plane, determine the direction of the shear displacement along the fault (right or left shear), reveal additional stressed conditions in the formation of the fault, and identify the compression and extension sectors. Approbation of these methods was carried out at the oil field of the Leno-Tunguska oil and gas province of the Siberian platform. Based on the results of the calculation, a small-scale map of fault tectonics was compiled within the studied oil deposit. Further use of this map is planned as a basis for calculating a 3D geomechanical model and selecting a development system. In the process of obtaining new information (data on core research, microimages, drilling data), a map of fault tectonics will be modified.

The main San Andreas Fault strikes subparallel to compressional folds and thrust faults. Its fault-normal traction is on average a factor of γ=1+2μthr(1+μthr2+μthr), where μthr is the coefficient of friction for thrust faults, times the effective lithostatic pressure. A useful upper limit for μthr of 0.6 (where γ is 3.12) is obtained from the lack of heat flow anomalies by considering off-fault convergence at a rate of 1 mm/yr for 10 km across strike. If the fault-normal traction is in fact this high, the well-known heat flow constraint of average stresses of 10–20 MPa during strike slip on the main fault becomes more severe. Only a few percent of the total slip during earthquakes can occur at the peak stress before dynamic mechanisms weaken the fault. The spatial dimension of the high-stress rupture-tip zone is ∼10 m for γ = 3.12 and, for comparison, ∼100 m for γ = 1. High dynamic stresses during shaking occur within these distances of the fault plane. In terms of scalars, fine-scale tectonic stresses cannot exceed the difference between failure stress and dynamic stress. Plate-scale slip causes stresses to build up near geometrical irregularities of the fault plane. Strong dynamic stresses near the rupture tip facilitate anelastic deformation with the net effects of relaxing the local deviatoric tectonic stress and accommodating deformation around the irregularities. There also is a mild tendency for near-fault material to extrude upward. Slip on minor thrust faults causes the normal traction on the main fault to be spatially variable.