As a result of 3D numerical modeling of the hydrocarbon systems (HS) in the South Caspian Basin (SCB), three classical generation–accumulation hydrocarbon systems (GAHS) – Eocene–Pliocene, Oligocene–Miocene–Pliocene, and Miocene–Pliocene– and three unconventional (shale) HS–Eocene, Maikop, and diatomaceous – have been identified. They are associated with highly productive oil and gas source rocks (OGSR) within the sedimentary cover. The study integrated basin modeling, geochemical data, and tectono-sedimentary analysis to reconstruct the spatiotemporal evolution of hydrocarbon generation, migration, and accumulation processes. The results reveal that the SCB is a multifocal basin containing several stratigraphically and hypsometrically isolated autonomous hydrocarbon generation centers. These centers correspond to zones of maximum thermal maturity and transformation ratio (TR) values, indicating peak hydrocarbon generation. Vertical migration of hydrocarbons from the OGSR occurs along disintegration zones and faults, often associated with mud volcano activity. Modeling established the «critical moment» – a geological time marking 50% realization of the generation potential and the onset of mass hydrocarbon migration. Oils of the Pliocene reservoir represent mixed compositions derived from multiple source strata of Eocene, Oligocene–Miocene (Maikop), and Miocene (Tarkhan–Chokrak and diatomaceous) ages, with their relative contributions varying locally. The total volume of generated hydrocarbons in the SCB is estimated at 175.35 billion tons, with a residual potential of 67.4 billion tons, highlighting substantial remaining unconventional resources. The obtained results refine the understanding of petroleum system dynamics and provide a geodynamic basis for predicting new hydrocarbon accumulations in deep and unconventional reservoirs of the SCB.

Keywords: South Caspian Basin; oil and gas source strata; modeling; hydrocarbon systems; geodynamics.

Date submitted: 06.05.2025     Date accepted: 12.11.2025

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Oil shale is categorized as an unconventional hydrocarbon resource. The huge number of resources makes it a promising future energy supplier as a substitute for conventional oil resources. The Kohat Basin of Pakistan is rich in oil shale but has not been explored. In this work, the methodology used to evaluate the oil shale potential of Kohat Basin consists of geological surveys and sampling, laboratory experiments, and mathematical estimation. Geological surveys show the six potential formations with their further categorization. Numerous composite and non-composite oil shale rock samples were collected for analysis. Different laboratory analyses of these samples were carried out including evolved gas analysis (EGA), differential scanning calorimeter (DSC), thermogravimetry (DTG/TG), and differential thermal analysis (DTA). Geochemical analyses of the samples also helped to categorize the total organic content (TOC) of each geologic formation. The combustion and pyrolysis analyses of these samples revealed that the organic content varies between 8 to 80%. The other finding from the heat analysis methods helped to evaluate the properties and potential of oil shale in this region. Mathematical estimation, based on the output of heat analyses and dynamic kinetic studies, shows that the Kohat Basin hosts considerable oil shale reserves with deposits in areas such as Karak, Banda Daud Shah, and Dharangi. This comprehensive study provides useful insights into the oil shale potential of the Kohat Basin of Pakistan and also fills the information gap previously provided.

Keywords: Kohat Basin, oil shale, total organic content, unconventional hydrocarbon.

Date submitted: 06.05.2025     Date accepted: 06.10.2025

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In this work, the problem and methods of residual oil extraction, analysis and interpretation of oil-technological and physical-chemical data aimed at increasing the degree of oil extraction from depleted oil reservoirs in the fields of Azerbaijan were studied. The developed effective aqueous solution of surfactants together with air was pumped through an ejector into producing oil wells. The proposed system of oil reservoir processing and methods of intensifying the inflow of a solution of surface-active substances with air through an ejector increase the degree of oil extraction. They significantly improve not only the optimal modes of oil production, but also stabilize the development system, which has a positive effect on the final oil recovery. The developed surfactant solution and ejector allow for improved treatment of oil reservoirs and increased efficiency of oil extraction. The designations of the elements and the diagram of the developed ejector for feeding a surfactant solution with air into an oil well are given. The studies show that the highest oil recovery factor (≥ 50%) is possible in formations with an oil viscosity of 0.5–1.5 mPa⋅s. At higher oil viscosity values, the efficiency of the solution injection method for extracting residual oil is low. The experiments were carried out at production wells No. 1580, 1858, 1715 and injection well No. 1544 «Siyazaneft» of PO «Azneft». The results of the experiments conducted in the fields of Azerbaijan showed that the ejector we developed and used allows us to increase the efficiency of extracting residual viscous oil from depleted formations.

Keywords: enhanced oil recovery; ejector; surfactant solution; residual oil extraction method.

Date submitted: 21.04.2025     Date accepted: 18.12.2025

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The process of upscaling pore geometry, reservoir heterogeneity, capillary pressure, and other critical parameters plays a vital role in enhancing the effectiveness of reservoir characterization within reservoir simulations. Respective studies were focused on assessing the impact of laboratory-measured oil-water relative permeability data on predicting waterflood performance for the Chirag field within the GCA megastructure. This article delves into grid size sensitivity studies conducted using a cross-sectional model. These findings demonstrate that optimizing grid size significantly improves the match between simulated and actual field history. Moreover, the study emphasizes the importance of static reservoir parameters and aquifer size in shaping waterflood performance. By fine-tuning these parameters, a strong historical match was achieved for the A-6 well's performance with the optimized grid. This model was then leveraged to forecast water breakthrough for A-6z, an updip sidetrack drilled from the original slot. Predictions indicated that water breakthrough at A-6z was expected by late 2003. Notably, the timing of water breakthrough is influenced by the specific relative permeability data used in the model. Further exploration was conducted on
the effects of relative permeability and capillary pressure hysteresis, considering both drainage and imbibition curves. The results reveal a slightly earlier water breakthrough for A-6, along with a noticeable increase in the gas-oil ratio (GOR) trend. Detailed investigations into upscaling strategies for the fine grid model were also carried out, with pseudo-relative permeability curves generated based on Amoco rock curves, adding further precision to the overall reservoir simulation model.

Keywords: Chirag; pseudo relative permeability; simulation sensitivity; cross-section model; reservoir description; drainage and imbibition; grid-size; water breakthrough time; history matching.

Date submitted: 05.02.2025     Date accepted: 22.09.2025

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It was experimentally revealed that various fluids, when moving in microcracked channels with micron-sized openings, acquire new mechanical properties, which differ from their properties in the usual condition. The effect in the «microcrack-fluid» system is the reason for changes in the mechanical properties of fluids in microcracks and equivalent ultra-low-permeable porous media. It was revealed that when a one-parameter viscous fluid moves in a crack with an opening h < hcr, it becomes two-parameter, i.e. behaves like an anomalous fluid, and when moving with an opening h ≥ hcr, it restores one-parameter properties, and the anomalous fluid behaves like an anomalous fluid but increases the rheological constants of the model. By displacing Newtonian and non-Newtonian oil from plane-parallel microcracks with water and a solution of PAA polymers, the effect of pressure changes and crack openings on the oil recovery coefficient was studied. The displacement efficiency of non-Newtonian oil from microcracks using an aqueous PAA solution is approximately 20–22 % higher compared to displacement using pure water. For Newtonian oil, the improvement in displacement efficiency ranges from 5–15 % under similar conditions. In scenarios characterized by the «microcrack–fluid» interaction (i.e., when the microcrack width h < hcr displacement of both Newtonian and non-Newtonian oils should be performed using an aqueous PAA solution. This recommendation is particularly pertinent for non-Newtonian oils, as the enhancement in displacement efficiency is significantly greater than that observed for Newtonian oils. To increase oil recovery in microcracked and low-permeability porous media, it is recommended to take into account the «microcrack-fluid» effect.

Keywords: microcrack opening; non-Newtonian fluids; shear stress limit; structural viscosity; displacement coefficient; «microcrack–fluid» effect.

Date submitted: 15.07.2025     Date accepted: 19.12.2025

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This paper investigates the impact of residual or injected water on the component composition of produced natural gas, with a particular focus on mutual dissolution and evaporation/condensation processes between water and hydrocarbon components under reservoir conditions. The study is based on experimental investigations conducted using a specially designed laboratory setup and methodology that replicates reservoir conditions, including the influence of a porous medium on gas-condensate production performance. The analysis centers on the dynamic changes in gas composition during differential condensation at varying levels of residual water content and pressure. The experiments conducted in the physical reservoir model demonstrate that increasing water saturation in the porous medium significantly alters the gas-condensate system composition. This is primarily due to the preferential dissolution of gas components with higher solubility in water. As a result, an increase in methane content and a corresponding decrease in heavier hydrocarbon fractions (e.g., C4+, C5+) per unit volume of produced gas are observed. Furthermore, as water content rises, the richness of hydrocarbon components in the gas phase diminishes, indicating a substantial shift in the gas–liquid equilibrium. However, these effects become less pronounced at lower pressure intervals, suggesting that pressure plays a critical role in governing phase interactions. The findings highlight that these compositional changes, driven by water presence and pressure variation, must be carefully considered in reservoir development planning and simulation models to ensure accurate forecasting and optimal production strategies.

Keywords: gas condensate reservoirs; Retrograde condensation; Bottomhole pressure; Wellhead pressure; Reservoir model; Flow in the wellbore.

Date submitted: 27.07.2025     Date accepted: 29.10.2025

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In the conditions of oil deposits with hard-to-recover reserves, the development of which is on the verge of economic profitability, confined to the Verey horizon and Bashkir tier of the Bashkir arch, Verkhne-Kamskaya and Blagoveshchenskaya depressions, the forecast of the oil recovery coefficient under the regime of oil displacement by water was carried out. Geological and statistical models have been constructed based on the use of more than 30 parameters characterizing the geological, physical, and physico-chemical properties of formations and their saturating fluids, as well as the technological parameters of the mining systems used. The models are constructed separately according to groups of selected objects and, in general, according to tectonic and stratigraphic elements in order to reduce the risks of making low-effective management decisions and expand the possibility of their integration into the real production process. It is shown that it is necessary to differentiate objects when solving development tasks, which makes it possible to mitigate the risks associated with a limited amount of geological and field data. The physical interpretation of the obtained models is given and their comparison with the current dependencies used in the construction of various characteristics is carried out. The obtained results are proposed to be used as an express method for estimating the optimal values of the well grid density and the ratio of the number of producing wells to injection wells after economic calculations. The use of the analogy method makes it possible to expand the resource base of liquid hydrocarbons of the Volga-Ural oil and gas province in the carbonate reservoirs of the coal system. 

Keywords: geological and statistical modeling; deposits of the Volga-Ural oil and gas province; method of analogies; hard-torecover oil reserves.

Date submitted: 11.06.2025     Date accepted: 13.12.2025

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48. Suleimanov, B. A., Veliyev, E. F. (2025). Methods for enhanced oil recovery: Fundamentals and practice. John Wiley & Sons.
49. Suleimanov, B. A., Rzayeva, S. J., Akhmedova, U. T. (2021). Self-gasified biosystems for enhanced oil recovery. International Journal of Modern Physics B, 35(27), 2150274.
50. Suleimanov, B. A., Ismailov, F. S., Dyshin, O. A., Veliyev, E. F. (2016). Selection methodology for screening evaluation of EOR methods. Petroleum Science and Technology, 34(10), 961-970. 
51. Suleimanov, B. A., Ismailov, F. S., Dyshin, O. A. (2014). Statistical modeling of life cycle of oil reservoir development. Journal of the Japan Petroleum Institute, 57(1), 47-57.
52. Andreev, A. V., Mukhametshin, V. S., Kotenev, Y. A. (2016). Deposit productivity forecast in carbonate reservoirs with hard to recover reserves. SOCAR Proceedings, 3, 40-45.
53. Mukhametshin, V. V., Kuleshova, L. S. (2019). Justification of low-productive oil deposits flooding systems in the conditions of limited information amount. SOCAR Proceedings, 2, 16-22.
54. Gilyazetdinov, R. A. (2024). On the possibility of integrated regulation of the operation of wells of the operational fund using dynamic reference models (using the example of the results of hydrochloric acid treatments of carbonate deposits of the Perm territory). SOCAR Proceedings, 4, 65-71.
55. Akhmetov, R. T., Malyarenko, A. M., Kuleshova, L. S., et al. (2021). Quantitative assessment of hydraulic tortuosity of oil and gas reservoirs in Western Siberia based on capillarimetric studies. SOCAR Proceedings, 2, 77-84.

Successful implementation of waterflooding technology depends largely on not only the appropriate selection of the development target; a reliable understanding of the physical mechanism of the process and its mathematical transformation into a hydrodynamic model are also crucial. Often, due to the complex geological structure of the development target, as well as excessive engineering simplifications regarding the physical mechanism of oil displacement by water, achieving perfection in waterflooding technology is not always possible. Scientists and experts ascribe a key role to the results obtained in the Buckley-Leverett two-phase filtration theory, which contemporaries and successors have questioned. The cause of this was the unstable behavior of the oil-displacement front, leading to ambiguity and a jump (rupture) in water saturation, which in turn, under real reservoir conditions, triggers water breakthrough to production wells. Numerous attempts to solve this problem, presented in open sources, do not provide a comprehensive answer to this question. Given the importance and relevance of the problem, a new paradigm is proposed for predicting water breakthrough to production wells under unstable oil-displacement fronts during transient flooding. For this purpose, a mathematical framework is used—the equations of splitting polynomial autonomous dynamic systems (DSs) developed in catastrophe theory. Based on the new solutions, it is proven that the discriminants of the dynamic system equations for multiphase flow are quite suitable as a control parameter.

Keywords: geological and statistical modeling; deposits of the Volga-Ural oil and gas province; method of analogies; hard-torecover oil reserves.

Date submitted: 25.08.2025     Date accepted: 18.12.2025

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For the conditions of oil deposits with hard-to-recover reserves confined to the Famennian limestones of the South Tatar arch, a number of algorithms have been proposed to eliminate uncertainties in solving development tasks aimed at increasing the degree of oil reserves development. Using modern methods of processing geological and field information, the volume of data characterizing the features of the geological structure of objects, filtration and capacitance characteristics of productive formations and physico-chemical properties of the fluids saturating them has been processed. Various options for the occurrence of uncertainties and the directions of their removal are considered in order to create relevant scientific and methodological foundations for managerial decision-making in conditions of various levels of uncertainty. At the same time, the following options are considered: «noise» of information during hydrodynamic studies; lack of a set of data on the geological and physical properties of formations at the stage of deposit commissioning; lack of data from hydrodynamic studies; There is a need for differentiation and grouping of development objects that allow modeling of various processes that arise as part of the integration of modern
approaches into the production process. Based on the results obtained, geological and statistical models were built using various amounts of information and a set of parameters, which is the basis for removing uncertainties and reducing the risks of making low-performance management decisions. The use of current models makes it possible to significantly increase the effectiveness of planning and carrying out activities aimed at increasing oil recovery. 

Keywords: deposits with hard-to-recover reserves; geological and statistical modeling; the degree of development of oil reserves; management decision-making; algorithms for eliminating uncertainties.

Date submitted: 11.06.2025     Date accepted: 25.11.2025

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The development of hydrocarbon deposits requires constant improvement of methods of forecasting and production management. The creation and updating of geological and hydrodynamic models plays a key role in this process. Building and numerical experiments on a hydrodynamic model is a laborious process that requires significant time. The complex geological structure and poorly studied carbonate reservoirs add uncertainty to the process of hydrodynamic modeling. This, in turn, negatively affects the accuracy of forecasting such reservoirs. A variable approach with consideration of all uncertainty factors in some cases makes it possible to qualitatively improve the predictive ability of the model. This article is devoted to the description of the construction of a sectoral model of carbonate deposits of the Moscow stage at the site of a unique deposit in the Republic of Bashkortostan, based on the integration of the results of research work to refine the geological structure and modern geological data. As part of the work, an increase in the number of petrophysical dependencies used is proposed, which describe the facies variability of carbonate reservoirs in more detail. The integration of new data into the process of constructing and adapting the geological and hydrodynamic model made it possible to revise the distribution of reserves by area and section of the carbonate object. 

Keywords: carbonate deposits; Kashiro-Podolsk deposits; low-permeability reservoir; horizontal wells; core.

Date submitted: 18.09.2025     Date accepted: 08.12.2025

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Suboptimal oil cleaning during refining leads to water accumulation in pipelines, increasing hydraulic resistance and corrosion. Removal methods include mechanical pigs, chemical cleaning, and hydrodynamic removal by oil flow. Hydrodynamic methods offer key advantages: applicability across diameters and cost-effectiveness by eliminating specialized equipment. This review critically analyzes theoretical and experimental studies of multiphase oil-water flow, focusing on parameters affecting water displacement: pipeline slope, phase properties (density, viscosity, interfacial tension), and critical flow velocities influencing flow patterns. Synthesizing data from experiments and CFD simulations, a major challenge is the significant scale disparity: most experimental data originates from small setups (< 50 mm diameter), radically differing from real pipelines (> 530 mm). This gap raises concerns about the direct applicability of existing models due to unpredictable scaling effects. Furthermore, while similarity criteria (Reynolds, Froude, Weber, Euler, Bond numbers) provide useful force balance insights, they are insufficient for fully describing the complex, transient dynamics of water accumulation removal, as evidenced by the lack of consensus on removal mechanisms. Crucially, under typical pipeline conditions (flow rates near 1-2 m/s in large diameters), inertial and gravitational forces substantially outweigh interfacial tension (Bond number > 1). The review highlights unresolved issues in modeling transient interfacial phenomena and emphasizes the need for holistic analysis of the entire removal process – from accumulation to erosion to final removal. Consequently, priority research directions include experiments at larger, realistic scales (219–32 mm diameter), advanced CFD techniques (LES, DNS), high-fidelity diagnostics like PIV, and developing integrated models simulating the complete water removal sequence. This provides a foundation for optimizing hydrodynamic cleaning in oil networks.

Keywords: multiphase flow; oil-water flow; two-phase flow; water accumulation; water removal.

Date submitted: 09.05.2025     Date accepted: 22.09.2025

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The article addresses the flushing of production wells in gas condensate fields with abnormally low reservoir pressures. It details the processes of formation damage in the near-wellbore zone caused by the use of technological fluids, identifying areas with reduced permeability. A system of criteria is proposed for selecting well flushing technologies under such conditions, based on technological, economic, and environmental indicators. Selection criteria are recommended with a focus on achieving optimal geological, technical, and economic results during well workovers, while meeting environmental protection standards and ensuring operational efficiency. The article analyzes the use of various technological fluids in well flushing during workovers in gas condensate fields at late development stages with abnormally low reservoir pressures. Technological fluid compositions and their application methods are studied and systematized, with a particular emphasis on optimizing their effectiveness. Requirements are developed to ensure effective well flushing while preserving reservoir integrity and minimizing environmental impact. The current state of technological fluids is described, emphasizing their ability to maintain reservoir filtration-capacity properties and prevent complications that could arise in the wellbore. The developed fluid compositions, due to optimized component ratios, reduce filtrate invasion and form weak intermolecular bonds with reservoir rock, thereby preserving the reservoir’s properties. Conditions for technically and economically effective well flushing under low-pressure conditions are identified, and fluid formulations have been optimized for field application. Overall, the article provides a comprehensive framework for selecting and applying well flushing technologies in challenging reservoir conditions, ensuring effective maintenance while safeguarding subsurface resources and protecting the environment from contamination.

Keywords: well; liquids; abnormally low formation pressure; filtration and capacity properties; flushing; compositions.

Date submitted: 02.06.2025     Date accepted: 29.10.2025

References

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14. Isayev, R. A. (2023). Analysis of distributions of petrophysical properties of sections and their relationship to loss of oil during well drilling in old fields with abnormally low reservoir pressures. SOCAR Proceedings, 1, 35-42.
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The authors of the article describe the results of a study of the effect of amphiphilic polymer solutions on the freezing temperature and number of asphaltene-resin-paraffin deposits (ARPD) of highly paraffin oil from the N. Narimanov field. The polymer was dissolved in toluene. The polymer mass fractions were studied by adding 8% (mass %) nonionic SAM to a solution with a polymer mass fraction of 2%. It was found that the composition with a polymer mass fraction of 2% was effective as an inhibitor against ASPO. The doses of the polymer mass fraction of 2% were studied at 10; 25.0; 100.0; 150.0; 200.0; 250 g/t; Due to the significant amount of toluene as a solvent, control experiments were carried out with pure toluene in the same doses. The experiments showed that toluene begins to reduce the freezing point of oil at a dose of 100 g/t. The maximum reduction is 3 °C at doses of 150 and 200 g/t. Addition of a polymer solution in the amount of 100 g/t begins to gradually reduce the pour point  of oil at the specified dose. At a dose of 200 g/t, the oil freezing point decreased from 21 to 3 °C. The effect against ASPO was 74.6%. Adding a polymer solution at a dose of 100 g/t begins to gradually reduce the oil freezing point. It is also noted that the polymer composition significantly improves the fluidity of oil, which has a positive effect on the viscosity of paraffin oils at the specified dosage.

Keywords: paraffin deposits; chemical inhibitors; polymer additive; nonionic substance; freezing point; kinematic viscosity.

Date submitted: 24.07.2025     Date accepted: 19.11.2025

References

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In mature oil fields, the physical characteristics of crude oil undergo significant changes as reservoir pressure and temperature decline. This decline is commonly associated with the practice of injecting cold water to sustain reservoir pressure, a method favored for its low cost. However, cold water injection increases oil viscosity, thereby reducing its mobility within the reservoir. Under such conditions, various thermal, thermochemical, and alternative enhanced oil recovery techniques are typically employed. To address this challenge, a heat-transfer fluid composed of lower alcohols, chromic anhydride, sulfonal, and seawater in specific proportions has been proposed. Chromic anhydride is a potent oxidizing agent, and its interaction with numerous substances generates substantial heat. Extensive laboratory experiments have demonstrated that raising reservoir temperature and lowering interfacial tension between the displacing and displaced phases can enhance oil recovery. Elevated temperatures are known to reduce both oil viscosity and interfacial tension, thereby improving displacement efficiency. The reagent under investigation meets these performance criteria. Moreover, the proposed formulation is capable of reacting with aromatic hydrocarbons and paraffinic compounds, yielding a range of acid esters, aldehydes, ketones, and other reaction products. These transformations further decrease interfacial tension and contribute to increased recovery. The surfactants included in the mixture moderate the reaction rate, which in turn expands the active treatment zone.

Keywords: composition; oil recovery coefficient; oxidizer; alcohols; surfactants; displacement.

Date submitted: 01.08.2025     Date accepted: 10.12.2025

References

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The complications associated with the use of technological pipelines in the oil and gas industry cause not only environmental issues but also economic losses. The high viscosity of the fluid transported through pipelines is one of the main factors causing to a decrease in transportation efficiency. In this regard, reducing the hydraulic losses caused by the viscosity of the transported fluid has always been relevant issue. Therefore, this study focuses on developing a new depressant composition to reduce the viscosity of high-viscosity local oils and improve their flow properties. Its composition consists of light pyrolysis tar, alcohol and aromatic hydrocarbon as organic solvents. The new depressant contains a light pyrolysis resin, alcohol, and aromatic hydrocarbons. The physicochemical properties of the new composition have been studied and the optimal concentration has been determined. The prepared composition reduces the viscosity of paraffinic crude oils in the optimal composition and has a positive effect on the fluidity properties. Based on the research findings, the consumption of the composition was determined to be 0.015-0.02 %. At the same time, the effect on asphaltene-tar-paraffini precipitation decreased by 2 times and the protective efficiency was 51%. When added to oil an optimal amount, the composition viscosity decreases from 18.5 mPa⋅s to 9 mPa⋅s. As a result of the research, it was determined that the developed composition has a high depressant function and can be used to reduce the viscosity and hydraulic losses of the fluid transported through pipelines. 

Keywords: viscosity; viscosity control; paraffin precipitation; depressant; aromatic solvent; alcohol; complexation; oil; freezing point.

Date submitted: 04.03.2025     Date accepted: 07.11.2025

References

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This study proposes an integrative methodology for residual life assessment of trunk gas pipelines in Kazakhstan, combining laboratory investigations of pipeline steel with digital analytics and machine-learning techniques. Most of Kazakhstan’s pipelines, built during the Soviet era, have exceeded their design life, creating risks of corrosion, embrittlement, and failure under aggressive operating conditions. The experimental program involved tensile, bend, hardness, metallographic, and chemical tests of two pipe specimens made of 17G1S-K52 steel. Results confirmed compliance with GOST 31447-2012 but revealed local anomalies: elevated carbon content (0.29 wt%) in one specimen, ferrite–pearlite banding, and pitting corrosion with FeS surface films. These features indicate potential risks of brittle fracture and stress-corrosion cracking. To complement testing, a dedicated software platform, GasPipelineInsight, was developed to process more than 20,000 in-line inspection records. The system integrates ETL operations, physics-informed feature engineering, and a Random-Forest classifier with 93% accuracy. Defect classification showed 67% of anomalies in category C (borderline), 1.5% in category A (safe), and none in category D (critical). Visualisation tools, including heat maps, histograms, and burst-pressure curves, supported decision-making and repair prioritisation. The findings demonstrate that integrating laboratory data with machine-learning analytics enables objective integrity ranking, early risk detection, and risk-based maintenance planning. The approach enhances the reliability and safety of gas-transport infrastructure and offers scalability for industrial application. Its adaptability provides potential for integration into national standards and for broader use in pipeline integrity management worldwide.

Keywords: residual life; trunk gas pipelines; in line inspection; machine learning; corrosion; burst pressure.

Date submitted: 08.09.2025     Date accepted: 19.12.2025

References

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The current state of electrochemical cathodic protection (ECP) systems used for offshore oil platform structures (OOPS) has been analyzed. Issues related to enhancing their operational durability and automating protection systems have been examined. The prevention or compensation of the chemical, physical, and biological effects of the environment has been identified as the primary objective. The study addresses the modernization of cathodic protection potential (CPP) monitoring devices and the automation of electrochemical cathodic protection stations (ECPS). Furthermore, new operational principles of transmitters for the automated control system (ACS) of cathodic protection stations (CPS) and the expansion of possibilities for their application have been investigated. Considering the relevance of corrosion protection for offshore structures, a semiconductor device has been developed to automate CPS units for platform supports and to regulate the output parameters of primary transmitters. The developed automated device reduces the number of cathodic stations required, making it possible to regulate the output parameters of several CPS units with a single device. The implementation of the automated CPS allows for significant savings in electrical energy, metal loss, and anode materials, while also expanding the effective protection zone of the cathodic system, thereby increasing economic efficiency. Thus, the main objective in the automation of CPS is to maintain the cathodic protection potential at a specified stable level, to design electronic modules based on modern component technologies, and ultimately to achieve higher efficiency and reliability.

Keywords: metal construction; corrosion; protection; station; automation.

Date submitted: 03.09.2025     Date accepted: 16.12.2025

References

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This study investigates the effect of aluminum foam fins and tube diameter (15 mm vs. 20 mm) on the electrical, thermal, and efficiency characteristics of a photovoltaic (PVT) system. The experiment was conducted in Al Marj, Libya, to test a photovoltaic (PV) module that included two passively cooled metal foam fin modules and an uncooled PV module as a baseline. Electrical performance, according to MATLAB analysis, improved from 14 to 17.5 % due to improved thermal control methods; however, thermal operating efficiency decreased from 43.9 to 31.3 % due to increased ambient heat loss. The experiments demonstrated that the 20 mm tube outperformed the 15 mm tube in terms of electrical (9.035% vs. 8.613%) and thermal (56.27% vs. 54.96%) output measurements at a flow rate of 0.17 kg/s. The highest combined efficiency measurements revealed that the 20 mm tube achieved an efficiency of 65.30%, while the 15 mm tube achieved an efficiency of 63.57%. The experiments underscore the need to optimize fins and tubes to achieve an effective combination of photovoltaic cooling and thermal efficiency. Future system improvements should focus on utilizing materials with high thermal conductivity properties, combined with enhanced fin-totube contact, to maximize system efficiency. The research results demonstrate the utility of combining photovoltaic thermal technology with aluminum foam fins for enhancing energy performance within oil production environments. The PVT system waste heat provides an additional benefit because it enables brine desalination, which subsequent operations need for separation and treatment functions.

Keywords: PVT collector, MATLAB software, sustainability, enhanced oil recovery, aluminum foam fins.

Date submitted: 20.02.2025     Date accepted: 21.08.2025

References

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The process of oligomeric oxypropylation of imidazolines obtained by interaction of a mixture of fatty acids of plant origin with polyamines was studied. Polyethylenepolyamines and their low-boiling components: diethylenetriamine, triethylenetetramine were selected as the latter. The mixture of fatty acids was obtained by a known method of saponification of soybean oil at boiling temperature with subsequent interaction with hydrochloric acid. The process of synthesis of imidazolines was carried out by selecting the molar ratio of the acid and amine components from the range of 1-2:1, preserving the reactivity of the final product due to the presence of amine fragments. Obtaining the products of oligomeric oxypropylation of imidazolines with the yield of ~97-98 % was carried out in a shaking autoclave reactor using different molar ratios of initial components. Imidazoline oxypropylates based on soybean oil fatty acids are viscous but dark-brown liquids that are fluid at room temperature. The structures of the final products were determined by IR spectroscopy, and a putative mechanism was studied. The patterns of the change of the main absorption bands (C-N, C=N, C-O, O-H) depending on the qualitative and quantitative composition of oxypropylates were studied. Good solubility of the synthesized compounds was revealed mainly in polar solvents, as well as in individual non-polar solvents. Due to the manifestation of surface-active properties, studies of synthesized oxypropylates as an oil-collecting reagent from the surface of various natural waters in case of accidental spills, as well as oil production from offshore fields are being successfully conducted.

Keywords: fatty acids of soybean oil; imidazolines; propylene oxide; polyamines; oligomeric oxypropylates; IR spectra.

Date submitted: 27.01.2025     Date accepted: 23.09.2025

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In the research work whose results are presented in the article mono-, di-, and tri- sodium and potassium salts of propylamides of ethylenediaminetetraacetic acid were synthesized to test their efficiency as corrosion and salt deposition inhibitors. 10% solutions of salts were prepared to determine physicochemical properties such as density, kinematic viscosity, freezing point and refractive index, while structures of synthesized compounds were confirmed using IR spectroscopy methods.It was determined that when salt was added to the medium at concentration of 50 mg/l, the trisodium salt of the amide synthesized from ethylenediaminetetraacetic acid and propylamine in a 1:1 molar ratio yielded the best results. Specifically, at this concentration, it protects the metal plate from corrosion by 94% and demonstrates a salt deposition inhibition effectiveness of 96%. The effectiveness of the salts against corrosion and salt deposition was also studied at concentrations of 100 and 150 mg/l, and it was determined that an increase in concentration is directly proportional to effectiveness. Simultaneously, during the analysis of results it was revealed that the mono-, di-, and trisodium salts of propylamides of ethylenediaminetetraacetic acid exhibit higher inhibitory properties against corrosion and salt deposition compared to their corresponding potassium salts. In terms of activity, the ranking for both sodium and potassium salts was mono- < di- < tri-. In various industrial sectors where water is used, such as mines, raw material transportation via pipelines, heating and cooling systems the highly effective samples can be applied as active components of reagents against corrosion and salt deposition problems.

Keywords: propylamide of ethylenediaminetetraacetic acid; corrosion protection; scale inhibition; corrosion and salt deposition inhibitor.

Date submitted: 05.06.2025      Date accepted: 29.10.2025

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The article presents the results of anticorrosive gravimetric studies of pyridinium salts obtained based on 4-isooctyl-phenoxy-3-propyl- and 2-diethylaminomethyl-4-isooctylphenoxy-3-propyl bromides (compounds I and II, respectively) on St.3 steel in water-salt-hydrocarbon environment, saturated with hydrogen sulfide, as well as in 0.5 N H₂SO₄ at temperatures of 298, 303, 313, 323, 333 K and their concentrations of 0.025, 0.05 and 0.1 g/L. Compound I was obtained by condensation of isooctylphenol with 1,3-dibromopropane and next reaction of the obtained bromine-containing ether with pyridine. Compound II was obtained by condensation of the aminomethyl derivative of 4-isooctylphenol with 1,3-bromopropane and subsequent quaternization of the intermediate compound with pyridine. Their yields of the compounds are 90 and 93%, respectively. As a result of the studies, it was found that compounds 1 and 2 showed comparatively higher activity in a sulfuric acid environment. It was found that both compounds have good protective properties. The maximum corrosion protection efficiency (Z) of compound I is 96.1% at a concentration of 0.1 g / L and a temperature of 298 K. Compound II is superior to compound I in its inhibitory properties and under the same test conditions (298 K, 0.1 g/ L) reaches 99%, which can be explained by the additional contribution of the aminomethyl group in the process of formation of a chemisorption film on the metal surface. Some thermodynamic parameters of adsorption (ΔGads, ΔHads, ΔSads) were calculated and, based on the results obtained, a chemisorption (blocking) mechanism for protecting the metal surface from corrosion was proposed. The adsorption process is described by the Langmuir isotherm.

Keywords: corrosion inhibitors; alkylphenol derivatives; nitrogen-containing compounds; pyridinium salts; adsorption.

Date submitted: 09.06.2025     Date accepted: 13.11.2025

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In the process of preparing gases for transportation and processing, the hydrocarbon condensate separated in the separators contains a certain amount of dissolved methanol. In the further processing processes of the condensate, along with the raw materials, methanol and formation waters dissolved in it also enter the processing facilities. This creates additional problems in later stages. The purpose of the work is to remove the methanol and water contained in the raw material during the processing of a large fraction of hydrocarbons. The «methanol water-hydrocarbon condensate» system and the mutual solubility of these components were studied. It has been proposed to use an absorption process to remove methanol from a wide fraction of hydrocarbons, and to use CaA-brand synthetic zeolite as an adsorbent, which is more active than others and is economically viable. The research work was carried out in a test facility under laboratory conditions. Based on the results of the conducted studies, the adsorption isotherms of CaA zeolite with respect to methanol, the dynamic activity of the zeolite layer with respect to methanol at different temperatures, the dependence of their dynamic activity on the flow rate at different heights of the zeolite layers, the kinetic curves of methanol desorption and the decrease of the activity of zeolite depending on the working time were studied.

Keywords: hydrocarbon condensate; fraction; adsorption; zeolite; dynamic activity; desorption; isotherms; temperature.

Date submitted: 21.06.2025     Date accepted: 19.11.2025

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The efficiency of any commercial company is characterised not only by its profitability (profitability), but also by the dynamics of its value (capitalisation). In conditions of high volatility of stock exchange quotations of equity securities of Russian companies, the relevance of improving the tools for prospective assessments increases. The main objective of this study is to develop a toolkit (based on the application of artificial intelligence) for high-precision forecasting of the exchange rate value of ordinary shares of large Russian oil and gas companies (Rosneft, Lukoil and Surgutneftegaz). The initial information is daily quotes (closing prices) of ordinary shares of Rosneft, Lukoil and Surgutneftegaz on the Moscow Exchange for the period from 06.01.2014 to 09.10.2024. Neuromodelling is performed first in NeuroSolutions for Excel, then in Google Colab (Python programming language is used). In the first case, computational experiments are performed for artificial neural networks of 5 different topologies (MLP, GFF, MNN, JEN and PCA). In the second case, an artificial neural network of a relatively new topology, LSTM, is used. Computational experiments allowed us to confirm the hypothesis about the possibility of highly accurate forecasting of closing prices of Rosneft, Lukoil and Surgutneftegaz ordinary shares using an ensemble of artificial neural networks of different topology. The results obtained in this study provide a scientific basis for assessing the role of the management factor in changes in the capitalisation of Russian oil and gas companies. It will also be possible to correctly distinguish the influence of factors of speculative and non-speculative nature on the volatility of the companies' value.

Keywords: Russia Value (capitalisation); Oil and gas companies; Ordinary shares; Closing prices; Forecasting; Artificial neural networks; Multilayer perseptron; LSTM.

Date submitted: 14.04.2025     Date accepted: 04.11.2025

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This article examines the prospects for joint projects between Kazakhstan and Azerbaijan in the oil and gas sector and identifies effective management models for such cooperation. The study employs a multi-source research design, combining: (1) analysis of legal and regulatory frameworks, including primary petroleum legislation, production sharing agreements (PSAs) and bilateral treaties; (2) review of institutional and project management structures, such as joint ventures, consortia, public–private partnerships and the roles of national oil companies (KazMunayGas and SOCAR); and (3) assessment of the broader geopolitical and economic context through policy reports, documents of international financial institutions and energy market outlooks. Empirically, the paper uses case studies of the Baku–Tbilisi–Ceyhan (BTC) pipeline, the North Caspian Sea PSA (Kashagan), and recent SOCAR–KazMunayGas transit arrangements to illustrate concrete models of cross-border cooperation and risk-sharing. The analysis shows that, while both countries have successfully leveraged PSAs and JV structures to attract capital and technology, their legal trajectories diverge: Azerbaijan has prioritized long-term contract stability, whereas Kazakhstan has gradually shifted toward stronger state participation and revised fiscal regimes. The paper argues that future Kazakhstan–Azerbaijan projects—particularly in trans-Caspian transit and regional connectivity—will depend on clear and predictable legal frameworks, balanced JV/PPP structures, and the involvement of international financial institutions to mitigate political and financing risks. These elements form the basis for more resilient, diversified and mutually beneficial energy cooperation between the two states. 

Keywords: Kazakhstan; Azerbaijan; oil and gas industry; production sharing agreements; joint ventures; public–private partnerships; Caspian Sea; energy security; foreign investment; trans-Caspian cooperation.

Date submitted: 30.07.2025     Date accepted: 26.11.2025

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The article empirically investigates the factors affecting the behavior of investment inflows into the oil and gas sector of the Republic of Azerbaijan under conditions of uncertainty. The study assessed short-term and long-term relationships between oil price volatility, Economic Policy Uncertainty index (EPU), exchange rate, interest rate, and fiscal support indicator based on annual data from 2000–2024 applying the ARDL (Autoregressive Distributed Lag) model. Structural breaks associated with the 2015–2017 devaluations and the 2020 COVID-19 shock were considered through dummy variables. The empirical results indicate that higher oil prices significantly increase the long-run level of investment volumes, while volatility and policy uncertainty exert negative effects. In addition, exchange rate stability and fiscal stimulus play an important role in restoring investment. In the short term, oil market shocks trigger a stronger reaction, but regulatory policy mechanisms mitigate these effects. The findings suggest that building a sustainable investment framework in the energy sector requires fiscal stability, reduction of currency risks and transparency of economic policy. The results have practical importance in energy strategy formulation, planning of public investment programs and risk management. 

Keywords: oil prices; price volatility; economic policy uncertainty; investment; energy sector; Azerbaijan economy.

Date submitted: 01.10.2025     Date accepted: 25.12.2025

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Azerbaijan has considerable geothermal energy potential. The resources are concentrated in regions such as the Absheron Peninsula, the Greater and Lesser Caucasus, the Kur Basin, and the Pre-Caspian-Guba region. Although the country does not have active volcanoes and geysers, geothermal energy can be extracted from deep wells, abandoned hydrocarbon fields, and natural hot springs. This study analyzes and maps Azerbaijan’s geothermal resources using a Geographic Information System (GIS) to assess their potential for power generation and direct use. The main results show that wells such as Jarly-3 field thermal fluids with temperatures of up to 96 °C. Other promising sites include Daridagh in Nakhchivan and the Shikh field in Absheron, where geothermal water with a temperature of 68 °C. GIS-based interpolation techniques, including Kriging and Empirical Bayesian Kriging were applied to model the subsurface temperature distributions and identify regions with the highest geothermal potential. The study analyzed data from over 500 hot springs and geothermal wells to determine temperature variations at different depths. The results indicate that Azerbaijan’s geothermal resources could support applications ranging from electricity generation to heating, agriculture, and industrial processes. Developing these resources could diversify Azerbaijan’s energy sector and reduce dependence on fossil fuels. This study highlights the need for further exploration, improved drilling technologies, and investment in geothermal infrastructure to unlock the full potential of Azerbaijan’s geothermal reserves.

Keywords: Geothermal energy; GIS mapping; geothermal wells; renewable energy; Azerbaijan.

Date submitted: 30.01.2025     Date accepted: 20.11.2025

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In this work, a computational algorithm for determining the fractional order in oscillating systems with liquid dampers occurring in sucker rod pump units is presented. The study particularly focuses on cases where the liquid mass inside the cylinder is sufficiently large, as typically observed in such pumping systems used in oil extraction. These systems exhibit complex dynamic behavior due to the interaction between the rod string and the fluid column. The proposed algorithm provides a more accurate representation of the fractional damping effect and can be effectively applied to improve the modeling, analysis, and optimization of sucker rod pump installations. An asymptotic method is introduced to solve the problem by introducing the inverse value of the mass as a small parameter. At this time, the obtained equation is reduced to the Volterra integral equation of the second kind with respect to the second order derivative of the phase coordinate. Then, an asymptotic separation is introduced to solve the equation. This separation is taken into account in the obtained Volterra integral equation and integrated twice, as a result, the solution of the equation is obtained. A quadratic functional is constructed using statistical data. The obtained solution and statistical data are taken into account in the quadratic functional. Using the least squares method, we ensure that the theoretical results coincide with the statistical data, and as a result, a more efficient fractional order is determined. Then, a calculation algorithm is proposed. Since some steps of this algorithm need explanation, the issue of the implementation of the algorithm is considered. 

Keywords: fractional order; oscillatory system; liquid damper; asymptotic method; Volterra integral equation; least squares method.

Date submitted: 17.08.2025     Date accepted: 24.11.2025

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For sections of the main gas pipeline, using an asymptotic representation of the power spectrum as a power function of low frequencies, an estimate of the possibility of self-organizing criticality was obtained by calculating the fractal dimension of the accident signal depending on its distance from the oil and gas production department. The main result of the work is the physically justified application of fractal analysis methods to the predicted expected phenomenon of self-organized criticality (SOC) of emergency situations on the main gas pipeline, as well as to the calculation of the precursor of an emergency (disaster), which provides an assessment of the degree of timely detection of an impending disaster. For this purpose, a method was developed for calculating the fractal dimension for a step function that registers a discrete signal. The phenomenon of the appearance of a harbinger of disaster is naturally associated with the most drastic changes in the difference moments of the 1st order and is provided by forecasting at the moment of the catastrophic state at the moment when the system is being rebuilt on all possible spatial scales. Еthe main requirement for the harbinger is fulfilled, namely, the displacement of the viewing window of the time series of the accident detection moments. To determine the precursor of a disaster based on data on accidents that occurred during the time interval under consideration [0, T], signaling algorithms x(t) are proposed with the fulfillment of the basic requirement by the time the disaster was detected.

Keywords: dynamic signal; precursor; power spectrum; autocorrelation function; Fourier transform; fractal dimension; selforganized criticality; step function.

Date submitted: 13.06.2025     Date accepted: 17.11.2025

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The article is of interest to the oil and gas sector, as the conducted research opens up new possibilities for the processing of petroleum hydrocarbons. Additionally, ultrasonic waves can be used to activate catalysts, thereby accelerating catalytic chemical reactions in industry. This study investigates the liquid-phase aerobic oxidation of paraffin concentrate separated from the diesel distillate fraction of Azerbaijani oil boiling at 135-360 °C, using ultrasonically treated fullerene soot as a catalyst. It is hypothesized that the radical and electrophilic properties of fullerene facilitate the activation of C–H bonds in alkanes, thereby enhancing its catalytic effectiveness in chemical reactions. Free radicals are essential for initiating and sustaining radical-chain oxidation processes. The fullerene soot contains 8% C₆₀ clusters. The analysis of Electron Paramagnetic Resonance confirmed that the fullerene soot contains carbon in a free-radical form. Thus, the presence of stable free radicals in the fullerene soot are confirmed. This property likely enhances its catalytic performance by accelerating the activation of C–H bonds in hydrocarbons and promoting the formation of oxygen-containing products such as synthetic fatty acids. The research revealed that at the use of 0.01% fullerene soot in the oxidation of paraffin concentrate it is exhibits catalytic properties and significantly accelerates the radical-chain oxidation process of hydrocarbons, promoting the formation of oxygen-containing products. However the presence of the ultrasonically treated catalyst best accelerates the reaction, doubles the reaction rate, and increases the yield of synthetic fatty acids. In the presence of ultrasonically treated fullerene soot, the acid number are reached 57.7 mg KOH/g within 4 hours, compared to 56.6 mg KOH/g after 8 hours with untreated fullerene soot.

Keywords: fullerene soot; ultrasonic waves in catalysis; oxidation; catalysis; paraffin concentrate; fatty acid; fullerene C₆₀.

Date submitted: 09.07.2025     Date accepted: 03.11.2025

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This study proposes a comprehensive approach to assessing the efficiency and sustainability of oil supply chains, taking into account the level of digital maturity as a key analytical parameter. This approach is described by a mod-el based on a hierarchical structure and includes min-max normalization, analysis hierarchy (AHP) weighting, and multi-level aggregation, allowing for the integration of operational, environmental, and technological indicators into a single composite index. Unlike fragmented methods that consider digital transformation, sustainability, or efficien-cy in isolation, the proposed model quantitatively reflects the relationship between digitalization and supply chain performance. Empirical data from large oil and gas companies and expert interviews confirmed the validity of the model. The model has been tested on a typical four-link supply chain (production, transportation, storage, distribu-tion), where a high correlation (r = 0.95) between digital maturity and integral productivity has been identified. The results point to key bottlenecks in segments with low levels of digitalization and demonstrate the model's potential as a strategic planning and monitoring tool. The methodology is adaptable to industry specifics, supports dynamic cali-bration, and can be applied in various industrial conditions. The integration of digital, sustainability, and operational parameters into a single assessment system provides a new level of manageability and adaptability of logistics pro-cesses in the context of digital transformation and environmental pressure. Thus, the presented approach can serve as a complement to existing approaches (SCOR, DESI, ESG), offering a holistic view of the relationship between digital maturity, sustainability, and supply chain efficiency. 

Keywords: integral index; digital maturity; oil supply chain; efficiency; sustainability; digital transformation. 

Date submitted: 02.07.2025     Date accepted: 19.11.2025

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