The present paper is devoted to the study of geological peculiarities of carbonate productive formations of oil fields and identification of correlations between filtration and capacitive properties of reservoirs with complex structure of void space. The dependence of reservoir permeability on its porosity, called petrophysical, is used in solving a wide range of problems, including geological and hydrodynamic modeling. Carbonate reservoirs have a complex void structure, which causes ambiguous petrophysical dependence and, consequently, insufficient reliability of calculations based on their application. Thus, with respect to the reservoir considered in this article, the standard petrophysical dependence is constructed differentially for pore and fracture type of reservoir voidness and is characterized by the values of the determination coefficient R²=0,81 and R²=0,16, respectively. An extended set of laboratory studies of carbonate core samples from one of the fields of the Perm region, including nuclear magnetic resonance, scanning electron microscopy, and X-ray computed tomography, allowed us to develop new dependencies that are valid for all types of voids and more closely link the filtration and capacitive characteristics of the reservoir (the coefficient of determination R² exceeds 0,92). The feasibility of using the developed equations was confirmed by conducting a computational experiment using a geological and hydrodynamic model of the considered reservoir. Replacement of the standard petrophysical dependence with the dependences obtained in the article allowed to improve the prognostic ability of the model for both differential and integral development indicators (annual and cumulative oil production, respectively). The results of the study and the applied approaches can be used in solving the problems of designing and modeling the development of carbonate reservoirs to improve the quality of adaptation of historical data in geologic-hydrodynamic models, as well as increasing the degree of reliability of the performed calculations due to a more detailed consideration of the features of the structure of the void space of the rock relative to traditional methods.

Based on the results of lithological, cyclostratigraphic analyses, as well as linking with geophysical research of wells data and correlation of well sections, the main isochronous levels of deposits of the Parfenovsky horizon in different facies zones of the Angara-Lena step were identified and traced. The sediments were formed in the conditions of coasts with wandering streams and tidal deltas passing into a shallow marine sedimentation basin. The lithological heterogeneity of the deposits is associated with a wide variety of medium-scale facies units (meso-facies), as well as the intensity and direction of secondary processes.

The paper presents the results of studying aromatic compounds (phenanthrenes, dibenzothiophenes, aromatic steroids) in source rock extracts (bitumoids) from the Bazhenov Formation of the Tomsk Region (south-east of Western Siberia, Russia). In addition to holonuclear and monomethyl-substituted structures of the phenanthrene and dibenzothiophene series we identified also their di- and trimethyl-substituted homologues. A comparative analysis of the relative concentrations of the main groups of aromatic compounds calculated by two methods (with and without di- and trimethylphenanthrenes and dibenzothiophenes) showed their identity. The main factor controlling the content and distribution of aromatic compounds has been established to be the degree of maturity of organic matter. The most informative molecular maturity indices for the Bazhenov Formation’s organic matter whose maturity corresponds to low and medium gradations of catagenesis (PK₃-MK₁²) are the ratios of 4-MDBT/1-MDBT, TASI, TAS/MAS, and TMTGP/1,7,8-TMP.

In order to correctly model the fluid phase behavior and accurately account for phase compositions, fractions and properties in the reservoir during the hydrocarbon field development, it is necessary in some cases to use non-equilibrium phase behavior models.

The signs of non-equilibrium phase behavior of hydrocarbons observed during field development may be associated with various factors. It has been experimentally shown that the so-called “thermodynamic non-equilibrium” behavior (when the phase transition cannot be considered instantaneous compared to the characteristic rate of change of the system state parameters) manifests itself due to the limited specific area of the phase interface. “Hydrodynamic non-equilibrium” behavior (the difference in actual fractions of the produced phases from the expected ones) is observed at high production rates for the reason that one of the phases does not have enough time to segregate and is transported as an aerosol in the second phase, without forming a separate continuous medium. Proper identification of the type of non-equilibrium behavior is a key factor in choosing the correct model.

The paper considers specifics of various models to account for non-equilibrium phase behavior. Examples of their practical application are analyzed for various manifestations of non-equilibrium phase behavior and different causes of its occurrence. The problem of modeling fluid flow with non-equilibrium phase transitions is discussed.

The article presents a petrophysical justification for the use of the method of reflected electromagnetic waves – electromagnetic common depth point method (ECDP) – for studying cryohydrogeological conditions and solving other geological problems. An analysis of the results of the ECDP experimental work on the territory of an oil and gas field in the Republic of Sakha (Yakutia) in 2023 was carried out, including a study of the obtained distribution of the interval velocity of the electromagnetic signal with depth in a number of measurements. The result of data processing is presented in the form of a “virtual well” – a vertical distribution of specific electrical resistance with a resolution of 2-5 m in depth. The reliability of the results of the ECDP is confirmed by their stable correspondence with all measurements taken and geological information at depths of at least 500 m, in particular the nature of the occurrence of frozen rocks and the position of water-saturated rocks. The advantages of the ECDP are shown, such as: sensitivity of the studied parameter (electromagnetic signal velocity) to changes in the physical properties of rocks, increased detail and the non-requirement of a priori geological and geophysical information for quantitative interpretation of measurement data.

This paper gives an overview of the results of deep geological and geophysical studies carried out in the south of Kamchatka and in the adjacent Pacific Ocean. The description of the volumetric density model and its analysis in conjunction with other data are presented herein. The data regarding the Tolmachevsky active magmatic center (TAMC) structural position and its origin is supplemented. The investigations allow to identify a closed-boundary mantle protrusion which has been formed in the Nachikinskaya transverse dislocation zone (Nachikinskaya TDZ) no later than the Early Miocene. The dimensions of the major and minor axes of the protrusion are 123 and 84 km, respectively. Localised areas of deconsolidation associated with melting chambers are identified in the lower part of the mantle protrusion at a depth of 35-45 km. The formation of the protrusion may be attributed to the pushing of magma of ultrabasic composition from the upper mantle and its subsequent intrusion into the lower layers of the Earth's crust. The intrusion takes place along the weakened zone formed at the initial stage of shear dislocation that has happened in the Miocene-Pliocene period. The differentiation of magma entering the Earth's crust from melting chambers as well as heat flows from the same sources form areas of focal melting and, as a consequence, lead to the formation of an intrusive massif of moderately medium acidic composition. Periodic magma advancement along the weakened zone in the TAMC area is accompanied by a series of weak earthquakes. The TAMC is genetically related to the mantle protrusion and forms an integral part of it.

The subducting oceanic lithosphere inflection zones are the areas of tectonic stress accumulation and its periodic release in the form of earthquakes. The highest density of seismic events with a magnitude M ≥ 5 is observed in the seismic lineament located closest to the coastline in the zone of maximum slab inflection in the depth interval of 30-50 km.

Currently, models based on the application of artificial intelligence methods are actively developed and applied in solving a variety of problems, including in the practice of petroleum engineering. Evaluation of the accuracy and reliability of the developed models is usually reduced to defining standard statistical criteria, while the developers do not always use a separate examination sample. This article presents the results of the study, which are reduced to multivariate testing of the neural network model previously developed by the authors to determine the dynamic reservoir pressure in the selection zones of oil wells. The model is characterized by a number of advantageous characteristics, including minimal requirements for the amount of initial data, which determines its relevance and practical demand. However, the closed nature of computational algorithms related to the "black box" category does not allow us to reasonably formulate the conditions and criteria for applying the model, the reliability of the retro- and prospective forecast of the reservoir pressure. Three oil deposits of one field with different geological and physical conditions were selected as the object of study. The availability of a large number of actual reservoir pressure determinations by means of hydrodynamic well testing at the field allowed testing the model under a variety of scenarios, for each of which the forecast error was estimated and analyzed. As a result, high estimates of the model for retro- and prospective reservoir pressure reproduction were confirmed. It was found that forecast errors are reduced to zero in the presence of a large number of actual reservoir pressure determinations. However, to perform the calculation for each well, a single measurement for the entire history is sufficient. It was found that a sharp change in the well flow rate should also be accompanied by an actual determination of reservoir pressure with the entry of the obtained value into the model. In the absence of even a single reservoir pressure measurement for the wells, the model reliably reproduces its value using the kriging procedure used in the algorithms.

The paper presents experimental results of studying capillary displacement curves in chemical methods of enhancing oil recovery. The analysis of the theory of capillary number and changes in this parameter in chemical methods of enhancing oil recovery is carried out. The results of studies of capillary displacement curves are analyzed and general patterns and features of the behavior of these curves in various experimental conditions are revealed. The analysis showed that with a change in formation wettability, porosity, permeability and pore structure, the capillary displacement curves change. Under changing formation conditions, classical capillary displacement curves previously obtained in the course of basic experiments do not allow predicting residual oil saturation, and in addition, the maximum oil recovery does not correspond to the maximum values of capillary numbers. In the practice of oil field development, there is no need to use high concentrations of surfactants to reduce the surface tension to an ultra-low level. Addition of polymer and alkali (in appropriate concentration) provides high oil recovery due to interaction of surfactants, polymer and alkali. Currently, in China, ASP flooding technology (alkaline-surfactant-polymer flooding - alkaline flooding and combined use of alkali, surfactant and polymer) is the most effective method of enhancing oil recovery in flooded oil fields and gives good results. Therefore, it is necessary to study the micromechanisms of residual oil mobility and filtration. Studies of the capillary displacement curve, considering the structure of the reservoir and its basic filtration characteristics, are of decisive importance in the development of oil fields in China, and these curves can also be used in world practice as a basis for enhancing oil recovery.

For the first time, information on the age of rocks – sources of zircon clastics for deposits of the Staropetrovo Formation of the Vendian Volga-Uralian sedimentary basin was obtained. As a result of U-Pb (LA-ICP-MS) dating of detrital zircons from sandstones of the Staropetrovo Formation in the well Krasnousolsk, located in the Pre-Uralian marginal trough, a wide time range of zircon clastic ages was obtained: from the Archean – 3247 million years to the Vendian – 577 million years. Features of the distribution of age populations of zircons from sandstones of the Staropetrovo Formation indicated the influx of detrital material into the Volga-Uralian basin mainly from local feeding provinces. The source of zircons of the most ancient (1831–2507 million years and 2660–2944 million years) population for sandstones of the Staropetrovo Formation is assumed to be the Archean-Paleoproterozoic formations of the Taratash metamorphic complex of the Southern Urals and crystalline rocks of the basement of the Volga-Uralian area. For detrital zircons with ages of 1472–1720 Ma, 1044–1390 Ma, and 653–736 Ma, corresponding to the early, middle, and final Riphean, the intrusive and volcanic formations of the Navysh, Mashak, and Igonino igneous complexes of the Riphean in the Southern Urals, which have modern isotopic datings for zircon and baddeleyite, and the basalts of the Aktanysh (well 203 Menzelino-Aktanysh) and Kipchak (well 1 Kipchak) volcanic complexes of the Volga-Ural region are considered as potential sources of zircon clastics, as well as the basalts of the Aktanysh (well 203 Menzelino-Aktanysh) and Kipchak (well 1 Kipchak) volcanic complexes of the Volga-Uralian area. In local feeding provinces, zircon sources with ages of 851–964 Ma and 603–643 Ma have not been established, which is most likely due to insufficient isotope-geochronological study of sedimentary and igneous complexes of the Precambrian of the East-European platform and its folded frame. Among the Precambrian formations, a special place is occupied by Vendian deposits, to which numerous manifestations of oil and gas are confined in the Volga-Uralian area, which makes Vendian deposits an attractive object for hydrocarbon exploration.

Borehole formation microimagers are a powerful tool for analyzing complex reservoirs, providing detailed information about the structural and textural features of formations. The development of state-of-the-art interpretation techniques can optimize existing approaches to microimager data analysis, enable the extraction of new object-level information, and significantly enhance the efficiency and quality of data interpretation. This study proposes a novel workflow for fullbore formation microimager data analysis based on processing a large and unique dataset using machine learning and computer vision techniques. The developed algorithms facilitate the automatic preprocessing of borehole microimager data and their automated structural and textural decomposition. The accuracy of object segmentation by convolutional deep neural networks exceeds 90%, while computer vision algorithms enable the analysis of the sizes, shapes, orientations, and topology of detected objects. The application areas of the proposed methodology include sedimentological analysis (thin-bed analysis); enhancement of core study workflow and formation tester evaluations (detailed characterization of reservoirs in intervals not covered by core samples); and advanced information for processing geological and geophysical data (reservoir modeling using deterministic approaches, distribution criteria for stochastic modeling and determining petrophysical parameters with high reliability).

Russia has the largest natural gas resource base. At the same time, a significant part of the gas reserves are classified as hard-to-recover reserves (HRR), and its supply to the market (primarily by pipeline transport) in modern conditions is associated with overcoming serious obstacles. Therefore, one of the key priorities for the development of the industry should be the production of high-tech gas – gas extracted from HRR or supplied to the market in the form of liquefied natural gas (LNG). Its production involves the use of both innovative technologies and new forms of coordination of participants in the processes of its production.

Projects for the production of high-tech gas can be successfully implemented only if a number of restrictions are removed. Particularly noteworthy are: (1) technological problems, the solution of which requires the use of new types of equipment, materials and services; (2) organizational and economic problems associated with an increased level of costs.

The authors' estimates show that the provision of additional tax preferences for the development of hard-to-recover gas – Achimov and Jurassic deposits – allows projects for their development to reach the level of profitability required by investors. At the same time, the state's tax revenues will be at the level of income received from the production of a similar volume of Cenomanian gas. This effect is associated with the mandatory inclusion of gas condensate in the composition of target products. In turn, when implementing LNG projects, even in the case of tax preferences, the state's revenues are no lower than with the existing taxation of gas production and its supply by pipeline transport. This circumstance is due to the fact that LNG-projects are characterized by higher capital intensity and greater flexibility in the directions of supply and subsequent use of liquefied gas.

It is shown that in order to increase the extraction and production of high-tech gas, an important role is played by the formation of conditions for the accelerated development of related industries, primarily oil and gas field services and mechanical engineering, which can only be ensured through close cooperation between the participants using indicative planning mechanisms.

In order to evaluate the oil and gas potential of the junction zone between tectonic structures of the southern part of the Laptev Sea and the Siberian Platform, the pods of active Upper Riphean, Vendian, Permian, Devonian and Upper Jurassic source rocks were identified and studied using numerical modeling methods. The impact of major tectonic shifts that occurred in the region during the second half of the Paleozoic and Mesozoic eras on the evolution of the source rocks was assessed. It was found that, except for the Upper Jurassic, all of the studied source rocks had passed the critical moment before the completion of major tectonic events in the region, which negatively impacted the formation of the hydrocarbon potential of the study area. As a result, low prospects are anticipated in the continental part of the junction zone, where small deposits are expected in the Vendian strata of the Lena-Anabar trough, given the presence of seals. A significant hydrocarbon potential, warranting further oil and gas exploration studies, is forecasted in the southern part of the Laptev Sea and the adjacent coast within the Anabaro-Khatanga saddle. The primary exploration opportunities in this region are linked to Permian and Mesozoic deposits.