The article discusses the current status and development prospects of the Saudi Arabian petroleum sector that is based on Saudi Aramco national oil company. Authors analyze resource potential and upstream policy of the kingdom. They study such competitive advantages of the Saudi oil and gas sector as low lifting costs and minimal carbon intensity, as well as Saudi Aramco’s strategic focus on maximization of the long-term value of hydrocarbon reserves. The article emphasizes that the following success factors enable the Saudi petroleum sector to maintain for many decades its leadership in the global oil and gas production: strategic vision of the kingdom’s rulers, constructive relations with international oil and service companies, wise fiscal policy, reasonable “Saudization” practices, partial privatization of Saudi Aramco, implementation of Saudi Vision-2030, efficient extraction of non-conventional hydrocarbon reserves, development and application of the state-of-the-art information technologies, and maximization of the human potential. A special focus is made on the comparative analysis of Saudi Arabia’s and the US energy policies, and their radical differences are identified. A conclusion is made that diverging models of Saudi and US petroleum sector’s development are equally viable given their specific political, economic and social environments.

   Interpretation of geological and geophysical data indicates an important role of Riphean strata in the formation of large and unique oil accumulations, which include the Romashkinskoye and Yaregskoye fields. Thermally immature Domanik shales in these areas could play only a supplementary role in the oil charging there. The formation of the unique oil accumulations of the Romashkinskoye field most likely was due to lateral migration of oil from the largest depocenter of Riphean sedimentation located in the Southern Urals. The huge size of the Riphean depocenter of the Southern Uralian Foredeep explains the anomalously high concentration of oil in the South Tatar arch. It is suggested that the Yaregskoye field was formed, also at least partially, by the oil charge from Riphean sediments overlain by the Timan Ridge overthrust. This fault created an extended tectonic contact between the
buried oil-producing deposits and the oil accumulation zone of the Ukhta High. Transit migration of oil took place through fractured allochthonous basement rocks.

   The article presents lithological studies of reservoir rocks of terrigenous deposits of the Lower Cretaceous of the Krasnoleninsky arch of Western Siberia. A distinctive feature of these deposits is the high variability of lithotypes, which is expressed in a wide range of textural features of the
deposits that determine the nature of oil saturation. According to the results of textural analysis, it was revealed that the studied sediments were formed in various zones of underwater channels of the delta complex and lagoons. To assess the total number of oil-saturated reservoir rocks and the degree of
their stratification, 10 models were selected that allow us to characterize the distribution of oil-saturated reservoir rocks in different facies complexes. The methodology developed at Gubkin University at the Department of Lithology made it possible to quantify the heterogeneity of the distribution of oil saturation in the multifacial deposits of the Lower Cretaceous of the Krasnoleninsky arch.

   In this work, a unique technique for replicating the void structure of a low-permeability reservoir in a silicon microfluidic chip has been developed. This technique is qualitatively superior to all previous ones and provides full repeatability of key parameters of the void structure (permeability; pore size distribution; average channel diameter; channel tortuosity, macro- to microporosity ratio) from digital core data. Moreover, the developed technique allows to exactly copy the pore geometry of the core sample from micro-CT images and recreate it inside the microfluidic chip. Using this technique, three artificial void space structures were developed for three samples of Achimov sandstones with different permeability (0.38; 2.04 and 9.86 mD). The mineralogical composition of the prototype samples was determined by a set of lithological and mineralogical studies and a positive correlation between the intensity of carbonate cementation and the decrease in permeability was revealed. Most of the macropores in the studied sandstones are associated with leaching of feldspars, and micropores are confined mainly to clay minerals. The conducted set of studies on the present samples will make it possible to extend the results of future filtration tests to rocks with similar mineralogical characteristics and filtration-capacitance properties. A qualitatively new method of creating inhomogeneous wettability of artificially created void space structure inside the microfluidic chip was developed. This technique consists in a smooth displacement of formation water from the microchip structure by a hydrophobic agent, which modifies wettability on the surface of macropores and channels, but does not enter the micropore structure due to residual water, which is held inside the microporous structures by capillary forces. Thus, this work is the first to apply a comprehensive multidisciplinary approach to replicate the core void structure within a microfluidic chip. In the future, this technique will be improved so that the results of filtration tests on microfluidic chips will even more reliably reflect fluid movement within the reservoir.

   Research subject. Mansurovo formation (the (?)Silurian–Lower Devonian) in the Western Magnitogorsk zone of the Southern Urals, outcropped in the same-name village vicinity.

   Aim. Clarification of the stratigraphy of the Mansurovo formation, detailing the composition and genesis of the litho- and volcaniclastic greywackes.

   Materials and methods. The geochemical and petrographic composition of the Lower and Middle Devonian sediments in the North of the West Magnitogorsk zone was studied using 122 samples analyzed by ICP-MS and XRF methods. Of these, 50 samples are greywackes of the Mansurovo formations. The composition of the provenance and the sedimentary environments of greywackes were studied based on the ratio of minor and major elements and the description of thin sections. Features of stratigraphy are considered on the basis of published and stock biostratigraphic data and a comparative analysis of the geochemical composition of greywackes.

   Results. The paleontological data accumulated to date are insufficient for confident dating of the Mansurovo Formation. Its age is conventionally assumed to be Silurian–Early Devonian. The ratios of minor elements in greywackes indicate the predominance of volcanogenic rocks of intermediate and basic composition in the provenance, which have geochemical characteristics of the formations of oceanic island arcs. The grain in graywackes is dominated by plagioclase and pyroxene porphyrites, crystalloclastics of pyroxenes and plagioclases. Of subordinate importance are grains of acidic volcanics, limestones, flints and siliceous-clayey rocks, microquartzites. The greywackes of the Mansurovo formation have a consistent composition and differ markedly in the ratio of certain elements from the tephrogenic rocks of the Irendyk formation, the Uskul formation and the greywackes of some sections of the Iltibanovo formation.

   Conclusions. The Mansurovo formation is an independent stratigraphic unit and cannot be combined with the Irendyk formation. A detailed clarification of the age of the Mansurov strata is required. Only after this can it be used as a standard for comparing and linking tectonically separated blocks of the Lower Devonian and (?)Silurian deposits.

   Studies were conducted on the sequence and conditions of authigenic mineral formation in fossil bone tissue, as well as the chemical composition and geochemical characteristics of fossilization processes in marine reptile vertebrae discovered in undivided Upper Jurassic clay deposits on the right bank of the Volga River (Tetyushsky District, Republic of Tatarstan). Using a combination of optical microscopy, electron microscopy, and spectral methods, the following set of authigenic minerals composing the fossilized remains was identified: fluor-hydroxyapatite, pyrite, barite, gypsum, anhydrite, siderite, calcite, hematite, goethite, lepidocrocite, quartz, and albite. The morphology, structural-anatomical features, mineral composition, and trace element content of the fossilized vertebrae indicate that sedimentation occurred under anoxic conditions on the floor of the Middle Russian Sea. Mineralization mechanisms included both biogenic (activity of sulfate-reducing bacteria) and chemogenic processes (seep-related activity), with the latter predominating. The sequence of mineral formation stages encompassed early and late diagenesis, catagenesis, and epigenesis (hypergenesis zone). Positive Ce anomalies (1.25–1.42) suggest a coastal-marine sedimentary environment in the Middle Russian Sea. The determined concentrations of rare earth elements and uranium are highly promising for further evaluation studies of bone-bearing deposits in the Oxfordian-Kimmeridgian clay formation.

   To evaluate the origin of cavernous hydrocarbon reservoir in the Lower Devonian dolostones (Western Taimyr, eastern coast of the Gydan Peninsula), the host rocks and the infilling carbonate minerals were studied using an integrated approach, including petrographic, cathodoluminescence, isotopic, geochemical and fluid inclusion studies. This approach showed that limestones that accumulated in the open subtidal shelf zone underwent dolomitization in early diagenesis, and dolomites with a fine-crystalline matrix were formed; the dolostones were significantly compacted during subsequent subsidence and geostatic compaction. The dolostones underwent fracturing the Late Hercynian tectonic phase (Late Carboniferous – Permian); fractures are associated with fissure caverns. Both fractures and caverns are partially filled with high-temperature generations of dolomite, quartz and calcite; low negative δ18о values and high positive Eu/ Eu* anomalies confirm their hydrothermal genesis. Similarity in PAAS-normalized patterns of Rare Earth Elements in the host rock and vein (cavernous) carbonate mineral indicates that the source for the infilling carbonate was the host rock. The results obtained show the high potential of using the applied approach in establishing the stages of development of a carbonate reservoir and for predicting its distribution in the section and area.

   The Chernoyarsk horizon of the Middle Devonian is one of the most poorly studied source rock in the south of the orenburg region. The data obtained from the results of drilling the first exploratory well on the territory of the Solnechnyj License area (LA) in the Rubezhinsky trough (southern part of the
Buzuluk depression) allowed us to obtain new information about the facies genesis and material composition of the rocks of the Chernoyarsk horizon, clarify their oil and gas production potential and update the concepts of the formation of the oil and gas potential of the region. Sedimentation in the lower part of the Chernoyarsk horizon occurred in conditions of a relatively deep sublittoral (below the wave basis), and in the upper part – in conditions of prodelta. In the rocks of the horizon, signs of bottom anoxia are observed – micro-bedding, abundance of planktonic and nectonic fossil of good preservation, rarity of bioturbation, abundant pyritization by organics. Integration of lithological and geochemical studies has confirmed the good generation potential of the oil and gas sorce rock of the Chernoyarsk horizon. The type of organic matter is defined as sapropelic (type II), the pyrolytic
parameter Tmax 448–459 ºC, which corresponds to the end of the oil window and the beginning of condensate/fatty gas generation. The values of total organic carbon (TOC) are ~ 2 % (rarely up to 5 %), which indicates a high degree of maturity and depletion of organic matter.

   The paper presents the results of laboratory studies of the physical and mechanical properties of carbonate rock cores from one of the oil fields in the Republic of Tatarstan. The experimental data obtained, together with the results of geophysical studies of wells and fracture data, were used to calculate the stress-strain state of the rocks. Horizontal stresses were calculated using the Eaton poroelastic model. The deformation coefficients at the depth of hydraulic fracturing were preliminarily determined. The minimum horizontal stress was determined as the fracture closure pressure, and the maximum horizontal stress was calculated from the stress diagram (combining the rock failure criterion and the classification of tectonic states). The elastic moduli obtained from laboratory studies were used in the stress reconstruction. As a result, the values of the stress along the borehole section were calculated and the tectonic regime was determined. The dependence equations for the strength properties of the rocks composing the section were obtained and the strength values along the entire borehole were calculated. The geomechanical model was used to calculate the dependence of fracture pressure on fracture length and to assess the conditions of uncontrolled fracture growth.

   The Gorevskoye deposit (Yenisei Ridge) is one of the largest polymetallic deposits localized in metamorphic rocks. Despite the long history of study, there is still no consensus on its genesis. Considering the important role of metamorphic transformations in recrystallisation and formation of ore appearance, assessments of the metamorphic conditions that affected the host rocks are the basis for reconstructions of the deposit genesis. Previously, such estimates were made approximately using mineral paragenesis in the rocks. This paper presents the results of studying the temperature conditions of metamorphic transformations of the host rocks of the Gorevskoye deposit using a geothermometer based on Raman spectrometry data of carbonaceous material, as well as traditional methods of mineralogical thermometry. The data obtained allowed us to estimate the peak temperature values of regional metamorphism at 490-530 °C with good convergence of the results of different methods. It is also found that the rocks were transformed by hydrothermal processes at temperatures around 345-365 °C during the post-metamorphic stage.

   The study of native gold from several ore zones of the Pioneer field (Amur). In the samples found: nano-gold of various morphology, varying size and composition, as well as complex micro- and nanostructures (film, film layered rhythmic, globular, fine disperse, etc.). In clay-micaceous mineral phases associated with native gold, an isometric and spheroidal nanogold visible under an electron microscope with particle sizes ~ 30–600 nm and a composition of both pure gold (sample 1000 %) and silver impurities (sample ~ 980 %). In the matrix of the same mineral phases, an invisible ultra-thin nanogold was detected, which is recorded by energy dispersive X-ray analysis (size < 30–50 nm, its sample is 1000 %). The genesis of the above types of nanogold is associated primarily with imperfections (defects) in the crystalline structure of the minerals that make up the gold-associating rock. These defects were geochemical barriers on which thin and ultra-thin gold was deposited. A xenomorphic nano-gold is also mounted on the surface of a row of golden, with elongated shapes dominating the particles. The particle sizes of this gold range from the first tens of nanometers to 600–700 nm, although there are particles up to 1000 nm in length and sample 803 %. Various film and globular structures, represented by stratified rhythmic nano-formations consisting of alternating gold films, planar and curved films on the gold surface and globular particles, have been identified in a number of samples of native gold (globules) of gold. The thickness of the films generally varies in the range of ~ 50 to 450 nm, and the size of the globule – from 250 to 670 nm, the composition is different. Mean sample of gold films from the Southern Ore Zone 948 % in Intermediate 880 %. The complex structure of the gold with the presence of various micro- and nanostructures indicates the multi-stage processes of formation of native gold in different ore zones of the Pioneer deposit.

   A detailed study of gold from placers and eluvium of the ore zones of the Amazarkan deposit, located in the basin of the three upper tributaries of the Amazar River, was carried out. The placers are not very far from the primary sources. The supergene transformation of gold is weak and is expressed in the presence of high-fineness rims, petrovskaite rims, and newly formed gold on Au particles. Gold from eluvium is characterized by a fineness of 650–800 %. Endogenous features of the chemical composition are inherited by placer gold, but higher grade (above 850 %) gold predominates or is significantly present in placers. In gold ores (1,2) and placers (3–5), the following associations of mineral inclusions have been established: 1) chalcopyrite, sphalerite, Bi sulfotellurides (with Pb, Se); 2) galena, tetradymite, tsumoite, minerals of the composition BiPbTeS, SbPbBiFeTe; 3) arsenopyrite, pyrrhotite, gersdorffite, alloclasite, tetradymite; 4) galena, tetradymite, Bi-containing sulfosalts (with Pb, Sb, sometimes Se), tsumoite, aurostibite; 5) arsenopyrite, gersdorffite, cobaltite, galena, tetradymite, bismuthin. Nonmetallic minerals are represented by quartz, tourmaline, muscovite, siderite, potassium feldspar, and epidote. There is no relationship between the fineness of gold and the presence of inclusions of a particular mineral in it. Gold mineralization of different stages is spatially combined, and on the upper horizons of the ore bodies, gold was probably redeposited with coarsening and increasing fineness. Such gold is typical for placers of the Verkhny-Amazar ore cluster (Amazarkan, Bolshoy Amazar, Vasilievka rivers). Among the inclusions in gold, galena and Bi minerals predominate (association 4), association 3 is less common. The primary sources of gold from the Maly Amazar River placer probably largely include mineralization at a relatively deep level (mesothermal). Inclusions of Bi minerals in gold are rare; galena is associated not with them, but with arsenopyrite (association 5). The association of galena and Bi minerals in inclusions in gold is also typical for placers in other areas of eastern Transbaikalia, where gold mineralization is associated with granitoids of the Amudzhikan or Shakhtama complexes.

   The petrological and geochemical features of effusive and intrusive rocks of the Kutuevsky Au-Cu porphyry ore occurrence located in the zone of the Main Ural Fault in the Southern Urals were studied. The composition of the rocks was determined by chemical analysis, mass spectrometry with inductively coupled plasma on an ELAN 9000 quadrupole mass spectrometer, and also partially by atomic emission spectrometry with inductively coupled plasma on an ICPE-9000 spectrometer. It has been established that the Au-Cu-porphyry mineralization of the ore occurrence is associated with an volcano-intrusive complex, combining dolerites, basalts, basaltic andesites, their tuffs, gabbro-diorite and diorite intrusions. All petrochemical rock types have normal alkalinity. Dolerites belong mainly to the tholeiitic series, and basalts, basaltic andesites and intrusive rocks belong to the transitional tholeiitic–calc-alkaline series. The most likely mantle source of magmas for them was spinel peridotites, previously metasomatized by aqueous fluids that arose during the dehydration of slab rocks. At the initial stages of magma formation, a source similar in composition to the depleted mantle dominated, and later a more enriched mantle substrate was subjected to melting. Fractional crystallization played a significant role in the magma generation of effusive and intrusive rocks. The composition of gabbro-diorites and diorites was also influenced by processes of crustal contamination. It is assumed that the igneous rocks of the ore occurrence were formed in the back-arc basin of the frontal island arc of Late Emian age.

   The study focused on the Upper Famennian-Tournaisian formations in the southeastern part of Tatarstan, which constitute the stratigraphic sections of various segments of the Saraylinsky depression.

   The research aimed to develop a sedimentation model for the Upper Devonian-Tournaisian depositional complex within the Saraylinsky depression.

   Typical stratigraphic sections were constructed for different segments of the depression, and sedimentation patterns were examined for the margin, slope, and depression zones, based on a detailed analysis of core material from several wells. A consistent lithological succession was identified within the depression profile, revealing a rapid decrease in the proportion of carbonate deposits toward the axial zones, accompanied by an increase in mixed clay-carbonate-siliceous rocks with a high content of syngeneic organic matter. In the same direction, the thickness of coeval deposits decreases. The sections of the margin zone were formed in shallow-water carbonate shelf environments, whereas the axial zone sections represent more deepened intrashelf basins with signs of condensed sedimentation. Slope-type sections, in terms of lithological composition, show greater affinity with depression-type sections, although they exhibit characteristics of somewhat shallower sedimentary settings. A sedimentation model for the Upper Famennian-Tournaisian deposits within the Saraylinsky depression has been presented and described. The margin zones of the Saraylinsky depression are considered highly prospective for oil exploration, while the slope and depression-type sections may be regarded as potentially promising targets for shale hydrocarbon development with the application of appropriate technologies. The results of this study can be used in sedimentological research of other elements of the Kamsky-Kinelsky system of depressions, including the prediction of potentially promising areas for development.

   Domanic sediments extended on the area of Tatarstan Republic in the Volga-Ural petroleum basin are the object of the investigation. They are considered to be the main source rock of the territory.

   The goal is to assess their role in the oil bearing capacity of the region.

   It was determined that the domanic oil shale organic matter is predominantly immature, excepting areas on the north of the South Tatar arch and on the south of the North Tatar arch with kerogen maturity of early-middle oil window. The intervals with high porosity values (2-8 %) and increased oil saturation with fluids generated by domanic oil-source rocks were determined on these areas. The comparison with the Bazhenov deposits of Western Siberia was performed to determine the conditions of kerogen high maturity formation. As structural and tectonic factors that were determined on both Western Siberia and Volga-Ural areas may promote hydrothermal exposure, hydrous pyrolysis of domanic oil shale sediments was performed to assess their contribution the organic matter transformation. The results demonstrate higher generation capacity of the domanic oil shale kerogen compared to the Bazhenov formation kerogen, with 3.5 mg HC/g TOC of gaseous products and 185 mg HC/g TOC of liquid products generated. The obtained results can be used for promising zones on the territory of the Tatarstan Republic reconnaissance.

   The paper presents the results of studies on sandstones from the Vanavara and Oskobinskaya formations, which are part of the Nepa and Torskiy regional stratigraphic horizons, respectively. These formations were studied using the core from the Yur-92 deep well, located within the Kamov Arch of the Baikit Anteclise on the Siberian Platform. A detailed lithological description of a core with a total thickness of 89 meters is provided. For 13 sandstone samples, the following studies were conducted: petrographic analysis of thin sections, definition of major petrogenic oxide content, definition of impurity and trace element content using mass spectrometry with inductively coupled plasma, and geochronological (U-Pb) analysis of detrital zircon grains. It was found that the Vanavara formation is characterized by a terrigenous composition, while the Oskobinskaya formation is composed of terrigenous, sulfate, and carbonate rocks and can be divided into three members. According to the results of petrographic analysis of rocks from the Vanavara and Oskobinskaya formations, there is generally a similarity in terms of the degree of roundness and sorting of detrital material, as well as the composition of both rock-forming and accessory minerals including rock fragments such as quartzites, micaschists, and granitoids (both metamorphic and igneous rock types), as well as clay rocks, likely argillites. The material composition of all the studied sandstones from the Vanavara and Oskobinskaya formations corresponds to that of arkoses. Based on a set of lithogeochemical characteristics, it appears that the source material for the deposits of the Vanavara formation was primarily derived from rocks with an acidic composition, while the terrigenous rocks from the Oskobinskaya formation may have originated from both acidic and intermediate rocks. U-Pb (LA-ICP-MS) dating of detrital zircon grains from terrigenous rocks of the Vanavara Formation indicates that the main source of sediments in the basin where they were deposited was Archean and Early Proterozoic rocks from the Siberian Platform basement. The Oskobinskaya Formation was deposited as a result of the erosion of Archean, Early Proterozoic, and late Riphean rocks that formed the basement of the Siberian platform and the northern segment of the Central Asian fold belt, as well as possibly rocks that make up the East Angara Block of the Yenisei Ridge. Based on the characteristics of the Vanavara and Oskobinskaya formations, combined with the results of zircon dating and published data on lithofacies, it is suggested that the Vanavara formation was deposited on the passive margin of the Siberian platform. Then, there was a transformation into a peripheral foreland basin in which terrigenous rocks from the Oskobinskaya formation accumulated.

   The paper investigates the expediency of placement a water shut-off material in a high-permeability watered sublayer away from the injection well. This scenario of location the blocking agent with complex rheological properties in a reservoir requires reliable design and accurate control of execution, which significantly complicates the reservoir treatment process and, therefore, demands well-founded justification. The analysis of the impact of the viscosity ratio between the injected and produced fluids, as well the distance between the injection and production wells, on the effectiveness of shut-off measures was performed based on a series of multivariate simulations. The waterflooding process is simulated using g a high-speed computing two-dimensional model of stream tube with a computational block size of about 0.1 m. Applying of this a model allowed to reproduce small-scale hydrodynamic effects and the flow structure in the area of a relatively thin high-permeability sublayer and near the interval of its isolation with a high degree of detail. The fundamental dynamic structures of the waterflooding areas of the effective stream tube between the wells are introduced. The dependence of the optimal location from the injection well to the optimal location of the blocking material, which provides the maximum increase in oil recovery at a fixed level of water cut, on the variable parameters is revealed. A hydrodynamic analysis of various modes of waterflooding of the inter-well area of the formation is presented. This analysis simplifies the prediction and decision-making on the advisability of a remote location of the blocking material for a given ratio of phase viscosity and distance between wells.

   The presented analysis of the three-dimensional geological model of the Gorsky ultraviscous oil reservoir, located on the eastern side of the Melekess Depression (the border of the Republic of Tatarstan and the Samara region). The main productive proposals are relict-organogenic calcareous dolomite and oolitic calcareous dolomite of the Kazanian Stage. The geological model of the Gorsky reservoir included three models: lithologic-facies and petrophysical models and a saturation model. A lithofacies model, created to determine the nature of the spatial distribution of organogenic, oolitic and other marine formations, was used to reconstruct the paleogeographic sedimentation environment and showed that the stratigraphic sequence of carbonate sedimentation is represented in the form of eight stages.

   The purpose of constructing a petrophysical model and a saturation model was to determine priority directions for the development of the carbonate reservoir of ultraviscous oil of the Kazanian Stage.

   The authors assessed the oil-saturated volumes of rocks that have standard oil saturation within the main lithotypes. The share of relict-organogenic dolomite accounts for 60 % of the oil-saturated volume of rocks, and the share of oolitic dolomite – 40 %. Despite the fact that relict-organogenic dolomite is more oil-productive, it has worse reservoir properties. For the development of the Gorsky ultraviscous oil deposit, the priority areas are areas with improved petrophysical characteristics and a high oil saturation coefficient in combination with the use of steam-heat methods.

   The presence of fractures in reservoirs can have both a negative and a positive impact on the technical and economic indicators of field development and thus an early classification of fractures is an important requisite. Identifying the type of a fractured reservoir at the initial stages of development is a clue to selecting an optimal type of model and field development system. The paper evaluates the applicability of the cumulative production indicator and the productivity index of wells to determine the type of fractured reservoir with the help of a statistical method for analyzing the Lorenz curve and the Gini coefficient (as applied to determine the impact of fractures) with small data samples and at the initial stages of development. A method of mathematical statistics namely the bootstrap method is used in this paper in order to study the fracture impact coefficient for a small number of wells. This method is based on the repeated generation of random samples multitude from the original data set and their subsequent statistical analysis. Modeling of samples was carried out by means of a random number generator available in spreadsheets. The results of a research proved that the use of indicators such as cumulative production and productivity index to identify fractured reservoirs with a small number of wells produced the comparable results. To increase the reliability of classification for a small number of wells, a data sample is required that will most fully describe the field. It is possible to obtain a representative sample of data for an objective analysis of the distribution and influence of fracture systems by placing wells covering the entire area of the field. In the early stages of development, due to the low production volumes and short periods of well operation, it is recommended to use the productivity index for the analysis.

   A study of the structure of the carbonate Upper Devonian-Tournaisian clinoform complex of the Aktanysh-Chishminsky branch of the Kama-Kinel trough system was conducted using sequence stratigraphy approaches. The study used 2D and 3D seismic data, analysis of log curves and core material. The stages of formation of regional and subregional seals, as well as terrigenous and carbonate-terrigenous strata were interconnected. The stages of high standing of the relative sea level were revealed, when a steep marginal ledge was formed, controlling low-amplitude linear uplifts. It was concluded that the greatest prospects for oil and gas potential are associated with the Lower Tournaisian clinoform complex, which contains the highest quality reservoirs. Potential objects for the search for non-anticlinal hydrocarbons are considered – lenses of detrital limestones confined to the foot of the Lower Tournaisian accumulative slope.