The article investigates the spatial position of Upper Cretaceous volcanogenic formations and their oil and gas potential in the northwestern part of the Yevlakh-Aghjabadi Depression (YAD), located in the central part of Azerbaijan, based on complex geological and geophysical data. The main objective of the study was to determine the distribution areas of volcanogenic masses, the depth of their surfaces, their thickness, and their relationship with deep faults through modeling of magnetic field data.The conducted analyses showed that volcanogenic formations developed in limited but tectonically active zones in the north-western part of the YAD, and their distribution is mainly associated with deep faults. The surface of the volcanogenic formations is located at an approximate depth interval of 2.5-6.5 km from the ground surface, and their thickness varies between 800-3000 m across different areas. In some profiles, the thickness of volcanogenic masses exceeds 2-3 km, and it was determined that magma-feeding channels were formed in narrow zones (approximately 1 km). The maximum thicknesses of volcanogenic masses are observed in areas close to deep faults and gradually decrease toward the flanks. The high density and low permeability characteristics of volcanogenic rocks indicate that they can create favorable geological conditions for hydrocarbon accumulation by acting as a screening barrier. The obtained results confirm that volcanogenic formations in the north-western part of the YAD are closely related to the paleogeodynamic development of the region and play an important role in the formation of oil and gas systems.

Keywords: Yevlakh-Aghjabadi Depression; volcanogenic rocks; magnetic anomaly; ΔZ component; magma-feeding channel; volcanotectonic traps; reservoir-type anomaly; complex geophysical interpretation.

Date submitted: 19.01.2026     Date accepted: 08.04.2026     Date published: 20.05.2026

References

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In recent years, integrated geophysical exploration studies, incorporating seismic and gravimetric methods, have been implemented in the Kura Depression of Azerbaijan. Currently, there are broad opportunities available for conducting these research studies. Modern 2D and 3D seismic acquisition techniques that meet current industry standards, advanced gravimetric instruments (e.g., Scintrex CG-6 Autograv), and newly developed data processing and interpretation methods enable these challenges to be addressed at a high technical level. The obtained results indicate that the hydrocarbon potential of many fields has either been insufficiently studied or remains unexplored. The results obtained reveal the existence of new structural complexities and oil-and gas-bearing areas has been identified, and the possibility of discovering new deposits has been suggested. In the prepared article, the integrated analysis of seismic and gravimetric data was carried out for the Alimardanly uplift in the Kura–Aghstafa interfluve, combining gravimetric results with data from drilled wells. Additionally, along the profile crossing the western part of the Qamarli structure within the Ganja OGR, the study examined the geological structure and hydrocarbon potential of a high-amplitude new structural uplift, provisionally named the Western Qamarli. In the future, detailed integrated geophysical surveys-including seismic, gravimetric, and magnetometric methodsover the newly identified structural complexities and characteristic gravity minima (indicative of hydrocarbon potential) are expected to enable the discovery of additional oil-and gas-bearing fields and deposits in the Kura Depression. At the same time, leveraging the capabilities of gravimetric exploration will help reduce the risk of drilling non-productive (dry) wells.

Keywords: anomaly; characteristic gravity minimum; gravity force; gradient; Gravimetric exploration; high porosity; hydrocarbon potential; local maximum; regional profile; seismic exploration.

Date submitted: 04.03.2025     Date accepted: 25.02.2026     Date published: 20.05.2026

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Study of rock failure under excessive pressure drawdown is associated with the lack of an effective flushing system design. In this process, the filtration rate of drilling fluid through the bottomhole plays a key role. The pressure drawdown effect is fully realized when the rate of penetration exceeds the fluid filtration rate in both destruction and pre-destruction zones. If the penetration rate is equal to or lower than the filtration rate, the effect becomes only partial. The efficiency of a drill bit largely depends on the performance of its hydraulic system. The main criterion is the ability to promptly remove drilled cuttings from the bottomhole zone. To achieve effective cleaning, the flushing system must direct the drilling fluid, after reflecting from the bottomhole surface, toward the central channel of the bit. Such a flow pattern – from the periphery to the center – ensures efficient removal of accumulated cuttings. Various drill bit designs are currently used in well construction, making it important to evaluate their effectiveness under comparable rock destruction conditions. The primary performance indicator is the rate of penetration, defined as the volume of rock drilled per unit time. Deep well drilling practice shows that significant energy losses occur during transmission to the bottomhole due to depth. Under such conditions, abrasive-cutting tools are the most effective, providing high penetration rates with minimal energy consumption. Additionally, penetration per single impact is a critical parameter for selecting optimal drilling modes and ensuring maximum efficiency. This approach improves drilling performance, reliability, and overall operational stability.

Keywords: wells, mechanical model, centrifugal force, drilling, ball velocity, fluid viscosity, washing channel, graphical solution.

Date submitted: 19.11.2025     Date accepted: 20.02.2026     Date published: 20.05.2026

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To connect the stands in a drilling column, tool joints of various designs are used. During lifting and lowering operations, numerous operations involving tightening, loosening, and breaking-out operations of tapered tool joint threads are performed. During tightening and loosening, friction and wear of the tool joint threads occur both along the flat edges of the thread tops and along the side surfaces. Wear occurs both along the height and along the flank surfaces of the threads. The probability of contact and friction along the flat edges of the thread tops is 40%, and friction conditions are quite severe due to the small contact area. During tightening and breaking-out, friction and wear occur only along the side surfaces of the tapered threads. The performance of tool joint threads is limited primarily by a reduction in their effective height due to wear. Wear resistance is one of their primary operational requirements. The wear-resistant locking thread design, developed based on identified wear patterns during lowering and lifting operations and studies conducted on full-scale samples using a dedicated rig, eliminates friction and wear along the conical flat edges of the thread tops, increasing their wear resistance by approximately 1.7 times. It is applicable to all types of conical locking threads, is easy to manufacture and control, and requires only modification to the profile of the thread-forming tool. Its use in conical locking thread designs requires no additional resources or expenses, and increases the length of thread contact along the lateral faces of the profiles. 

Keywords: wear resistance; tool joint thread; tool; thread cutting; improvement.

Date submitted: 08.02.2026     Date accepted: 22.05.2026     Date published: 26.05.2026

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This paper presents the results of an offshore field trial conducted to evaluate a newly developed demulsifier under actual operating conditions. The primary objective was to identify a more suitable chemical formulation and assess its performance against existing operational specifications, while determining its impact on three-phase (oil–gas–water) separation efficiency under varying production conditions. The trial was conducted using a structured methodology designed to ensure a reliable performance comparison without interrupting production operations. The results confirmed that separation efficiency is strongly influenced by chemical formulation. Improved separation stability had a positive impact on overall process performance, including effective residence time, liquid slugging response, and thermobaric behavior. These findings demonstrate the importance of integrated chemical and process optimization rather than reliance solely on increased chemical dosage. The enhanced stability observed under transient inlet conditions and prevailing temperature ranges is largely attributed to the diesel-based carrier solvent, which improved oil-phase compatibility and ensured consistent transport of active components to the oil–water interface. Appropriate process optimization further supported compliance with oil export and produced water quality specifications. The field trial demonstrated stable three-phase separation performance with sustained compliance with operational specifications. Optimization of the demulsification program reduced chemical consumption, improved cost efficiency, and minimized logistics-related operational risks, providing a practical framework for offshore chemical evaluation and implementation.

Keywords: oil and gas production; temperature influence; demulsifiers; oil and gas separation; oil–water emulsions.

Date submitted: 03.03.2026     Date accepted: 04.05.2026     Date published: 20.05.2026

References

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This article is devoted to the development of improved drilling fluid formulations designed to combat complications encountered during deep well drilling. One of the key problems under such conditions is the presence of lost circulation zones, which lead to wellbore instability, sticking of drilling tools, and significant technological and material losses. The composition and properties of drilling fluids play a major role in this process. However, despite numerous studies, issues related to sealing properties still require experimental investigation of the isolating capacity of drilling fluids. Based on this, the article presents the results of experimental studies on changes in the resistance factor as a parameter characterizing the sealing properties of the fluid. During the research, the fundamental principles of experimental design theory were applied, along with statistical data processing methods to determine the significance of key factors and to model individual processes through calculations based on data analysis. In particular, correlation analysis using specialized software made it possible to study patterns occurring during the regulation of the composition and properties of drilling fluids and chemical reagents used to enhance wellbore stability and integrity during drilling. Laboratory tests were conducted, and sediment-gelforming compositions based on metallic and organic clusters and polymers were proposed to combat circulation losses. Experimental dependencies of the sealing capacity of the studied compositions on the concentration of these particles, polymer content, and medium permeability were obtained, enabling the selection of optimal combinations to achieve maximum efficiency in isolating loss zones.

Keywords: nanotechnology; drilling fluid; lost circulation; wellbore stability; reservoir isolation.

Date submitted: 23.05.2025     Date accepted: 09.02.2026     Date published: 20.05.2026

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Since oil and gas and gas-condensate reservoirs in fields consist of rocks such as sand, sandstone, limestone, dolomite, etc., the produced fluid contains aggressive solid particles of these rocks. The oil and gas composition includes formation water with high corrosive potential, containing components such as calcium chloride, sodium bicarbonate, magnesium chloride, sodium sulfate, etc. The presence of solid sand-clay mixtures and saline water in the collected and transported product leads to the erosion of technological equipment and premature failure of the working parts of pumps. To separate liquid and gas, the product often enters oil-gas separators with pulsations, which reduces the quality of gas separation from the liquid. Most of the sand-clay mixture coming from the wells reaches the water and oil collection tanks at the oil gathering stations and settles at the bottom. Cleaning the bottom sediments of existing tanks requires significant time, labor, and machinery, and exposes the environment to environmental pollution . When draining the water beneath the oil layer, oil is discharged out along with the water, leading to oil losses. To dampen pulsations in the oil-gas flow, a device should be installed at the inlet of the oil-gas separators to ensure the separation of sand-clay mixtures and the stabilization of surges. To drain the water under the oil and clean the tanks from salt and sand-clay sediment, the tank bottoms should be designed with a 1:30 concave conical ratio, and a drainage pipe should be placed at the center of the bottom.

Keywords: formation water; sand-clay mixtures; gas-oil-water mixture separator; settler; oil trap; oil suspension; emulsion; viscosity; Reynolds number; Stokes' law; separator; sand trap.

Date submitted: 11.08.2025     Date accepted: 31.03.2026     Date published: 21.05.2026

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The article examines contemporary solutions for optimizing gas-lift well operation modes. By analyzing flow conditions and the upward gas flow equation, the process of liquid displacement by gas within the annular space toward the tubing shoe was evaluated. Based on wellhead parameters and the downward gas flow equation, gas pressure at the shoe of the second-string tubing in a concentric dual-string configuration was theoretically determined. Furthermore, the gas injection velocity (υ ) at the shoe zone was calculated using a derived formula corresponding to the pressure at that depth. The correlation between gas velocity, liquid production, and gas injection rates was investigated. For this purpose, Q = f (V) and υ = f (V) relationships were established for five gas-lift wells based on field data and wellhead parameters. Results revealed a specific correlation between gas velocity at the tubing shoe and production rate, indicating that injection velocity at the entry point can effectively characterize the well's operation mode. To determine the optimal operation mode for gas-lift wells, Q = f (V) and υ = f (V) curves were plotted simultaneously. It was observed that the optimal mode determined from both graphs aligns at approximately the same point. Based on the results, it is concluded that the dependence of the liquid production rate on the operating gas injection rate can be substituted by the dependence of gas injection velocity on the gas injection rate for gas-lift wells.

Keywords: gas-lift wells; operating mode; tubing shoe; gas injection rate; gas injection velocity.

Date submitted: 13.01.2026     Date accepted: 13.04.2026    Date published: 21.05.2026

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At a certain stage of reservoir development, a number of operational challenges arise in well production. One of these issues is the ingress of water into the near-wellbore zone of the formation. Water breakthrough disrupts the normal operating regime of wells and leads to a sharp decline in production. The inflow of formation water into the well causes degradation of the near-wellbore zone, while sand carried by the water results in premature failure of downhole equipment. Consequently, frequent well shutdowns occur, and additional difficulties arise in oil treatment and transportation processes. Water production also adversely affects environmental and ecological balance. One of the main causes of water breakthrough is the heterogeneity of the near-wellbore zone in terms of permeability. The main objective of this study is to reduce the water-phase permeability of the near-wellbore zone. To achieve this, a new hydrophobic composition based on acidol and soapstock was developed, and its effectiveness in isolating water inflows was experimentally investigated under laboratory conditions. The results of the conducted studies indicate that injecting a volume of the composition equal to 15–17 % of the pore volume into the near-wellbore zone results in 12.7-14.5-times reduction in water-phase permeability, the water cut of the produced fluid decreases by 9.3–11 times, and the oil recovery factor increases by 11–14 %. 

Keywords: new treatment method; reservoir model; phase permeability; near-wellbore zone; isolation; hydrophobic; acidol; soapstock; oil recovery factor; water cut.

Date submitted: 15.12.2025     Date accepted: 20.04.2026     Date published: 21.05.2026

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Eliminating the technological difficulties encountered in the extraction, collection and transportation of gases through pipelines is one of the most urgent issues . The fact that the pressure of the gas in the pipelines remains practically stable, but the temperature changes intensively, creates technological difficulties in the system. In order to overcome these technological difficulties in the gas transportation system, the gas must be conditioned to meet required quality specifications to separate the liquid phase from gas streams, restore the steady operation of pipelines, and increase productivity. Taking these into account, the technological operating mode of the compressor station and individual units of gas-preparation facilities for transportation were studied. For this, in the process of drying gases, glycols are widely used. In order to increase the efficiency of gas preparation technology for transportation, absorbent polypropylene glycol, which has better properties than traditional inhibitors and is used in the process of gas drying, was prepared on the basis of local chemical products, using this inhibitor polypropylene glycol and this allows to obtain higher results. The technological mode of operation of individual units of gas-preparation facilities for transportation has been studied. Innovations were made to the technological scheme of the gas drying unit and an increase in efficiency was achieved. The absorbent is passed through mechanical and carbon filters to be cleaned of impurities and is fed to the regeneration unit through the pump. At the same time, the regeneration of this inhibitor takes place at a low temperature, i.e. 150–160 °C, which is economically profitable and used in production.

Keywords: gas; compressor; transport; equipment; thermobaric conditions; absorbent; moisture; separator.

Date submitted: 03.02.2026     Date accepted: 01.05.2026     Date published: 25.05.2026

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The physicochemical processes taking place in produced waters during oil and gas field operations are key factors that directly impact hydrocarbon production. The formation of salt sediments is of particular importance among these processes. Changes in temperature, pressure, salinity and ionic composition of produced waters lead to the precipitation of calcium, magnesium, barium and other ions in various sulphate and carbonate forms, forming poorly soluble compounds. These sediments accumulate in operating equipment, wellbores, tubing and collector array, leading to reduced production rate, equipment failure and increased operating expenses (OPEX). To prevent these problems, the chemical composition of the produced waters is continuously monitored during operation, the water compatibility is checked before injection, and special scale inhibitors are applied. Scale inhibitors are chemicals applied to prevent or slow the formation of hard-to-dissolve scale deposits in produced waters and process systems during the exploitation of oil and gas fields. Nowadays, it is possible to predict deposition risk in advance using thermodynamic modelling methods, which facilitates the making of more efficient decisions from both technical and economic perspectives. Thus, the correct assessment of the physicochemical processes occurring in wellbore fluids is one of the key conditions for the long-term and safe operation of oil and gas fields. For comparative evaluation in laboratory experiments, we used inhibitors developed by us under the conditional names “BR-2”, “KBRSAM-2”, “NKBR-14”, as well as foreign-made inhibitors “Inkredol” and “PAF-13”. Сonducted studies have shown that the inhibitor NKBR-14 has a higher protective properties than the other inhibitors. 40-50 mg/l inhibitor consumption showed a high protective effect against the precipitation of calcium and magnesium sulphate salts. 

Keywords: oil production; salt sediments; produced water; salt precipitation inhibitor; nanocomposition; protective effect; potassium sulphate; magnesium sulphate.

Date submitted: 08.11.2025    Date accepted: 05.02.2026     Date published: 25.05.2026

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High-molecular-weight asphaltene, resin, and paraffin (ARP) compounds present in produced crude oil tend to deposit on the surfaces of tubing strings, flowlines, sucker rods, and other production equipment as a result of temperature changes. Sand particles suspended in the oil, mechanical impurities, and inorganic salt crystals act as crystallization nuclei, further accelerating the deposition rate of asphaltene-resin-paraffin deposits (ARPD). The formation of these deposits reduces well productivity, leads to equipment failures, increases additional energy and material consumption, and decreases the mean time between repairs (MTBR). Several methods exist to mitigate these issues. Among the known approaches, the chemical method is the most advanced. It is considered one of the most efficient and promising approaches for controlling paraffin deposition in pipelines and wells. This method is characterized by high efficiency, relatively simple operational technology, and long-term effectiveness. To address the aforementioned problems, this study presents the laboratory test results of a newly developed reagent, NDP-22M-2, applied to several crude oil samples for the mitigation of ARPD, along with an explanation of its mechanism of action and determination of its optimal dosage. The mechanism of action of NDP-22M-2 is based on the formation of a polar layer on the surface as it renders the internal surface of equipment hydrophilic through wetting. Its operating principle relies on continuous dosing into the oil stream, which alters the surface properties of paraffinic crude oil and slows down the crystallization of solid phases. As a result, paraffin deposition is prevented, and the freezing point of the crude oil is significantly reduced.

Keywords: asphaltene–resın–paraffın deposıt; reagent; near-wellbore zone; viscosity.

Date submitted: 13.02.2025     Date accepted: 22.05.2026     Date published: 26.05.2026

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31. Mammadov, M. A., Yadigarov, T. A., Safarova, G. N., et al. (2024). Economic and mathematical modeling for risk assessment of innovative activities in an oil and gas enterprise. SOCAR Proceedings, 4, 139–146.
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Gas distribution companies face a practical problem that many anomaly detection methods do not fully address: detecting an abnormal reading is not enough if the reliability of the result is unclear. A sharp change in consumption may be related to a technical fault, an unusual consumption event, a metering problem, or a normal seasonal fluctuation. In such cases, the same statistical alert may require very different operational responses. This paper proposes a two-level anomaly detection framework based on Z-numbers, where each uncertain assessment is considered together with its reliability component. At the first level, lightweight methods, including Z-score filtering, moving average deviation, Isolation Forest, and PCA-based clustering, are applied to large-scale gas consumption time-series data to identify candidate anomalies. At the second level, each candidate is represented as a Z-number consisting of two components: a fuzzy linguistic assessment that describes the degree of abnormality, and a reliability measure that reflects confidence in that assessment based on data stability and methodological consistency. The output of the system is not limited to a binary anomaly label. Instead, observations are assigned to five risk classes, ranging from normal to absolutely anomalous, while the reliability component is presented together with each classification. The proposed system is implemented as a modular Python-based application supported by PostgreSQL and an operator-facing dashboard that presents risk distributions, detection results by method, and individual consumption profiles. The study shows that including reliability as part of anomaly assessment makes the output easier to interpret and more useful for operational decision-making in gas consumption monitoring. 

Keywords: gas consumption; anomaly detection; uncertainty; Z-numbers; soft computing; explainable analytics.

Date submitted: 02.02.2026     Date accepted: 05.05.2026     Date published: 21.05.2026

References

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In this article, the authors propose a composition for a polymer-containing drilling fluid and ways to reduce its loss during drilling of oil and gas wells. Theoretical aspects of drilling fluid loss are presented, including the characteristics and causes of fluid absorption by the rock. The main problems of drilling fluid loss associated with the instability of clay-argillite rocks of the South Torgay basin in Kazakhstan are described. The polymer-containing drilling fluid was obtained by adding polyacrylonitrile modified with fatty acid salts, which are a saponified fraction of the tar from the distillation of cottonseed oil fatty acids. The results of spectral studies of the modified polymer reagent polyacrylonitrile are provided. The authors present the results of studies on the effects of modified polyacrylonitrile, as well as crushed cotton stalks in various ratios on the properties of drilling fluid. These studies were conducted to reduce the rate of fluid loss through the borehole crust. Based on these conducted studies,on the effect of modified polyacrylonitrile and crushed cotton stalks on the rheological properties of the drilling fluid. A diagram of an experimental setup for determining the rate of drilling fluid passage through rock is presented, as well as when adding tar-modified polyacrylonitrile to the fluid. Existing methods for reducing drilling fluid loss are analyzed, and recommendations for implementation of this composition are proposed to increase the efficiency of the drilling process in complicated geological conditions.

Keywords: drilling; well; rock; loss (absorption); oil; gas; drilling fluid; tar; polyacrylonitrile; modification; spectroscopy.

Date submitted: 24.12.2025     Date accepted: 03.02.2026     Date published: 21.05.2026

References

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Reliable monitoring of gas pipeline operation is a critical task for ensuring the safe and efficient transportation of natural gas. Traditional inspection techniques, such as in-line inspection tools, provide detailed information; however, they are applied periodically and lack the capacity for continuous assessment of pipeline operating conditions. In contrast, SCADA systems generate large volumes of real-time operational data, including gas flow rate measurements, which can be effectively utilized for online monitoring purposes. This paper proposes a fractal-based approach for monitoring gas pipeline operation using SCADA flow rate data. The proposed methodology is based on the analysis of flow rate time series to identify fractal characteristics associated with different operating regimes of the pipeline. Fractal indicators, including the fractal dimension and long-range dependence measures, are employed to quantify the complexity and variability of gas flow dynamics. Changes in these fractal parameters are analyzed to distinguish between normal steady-state operation and disturbed operating conditions caused by transient regimes, demand fluctuations, or potential anomalies. The approach allows the extraction of informative features from flow rate data without the need for direct physical inspection of the pipeline. The results demonstrate that fractal indicators derived from SCADA flow rate signals are sensitive to operational changes and can serve as reliable diagnostic parameters for pipeline monitoring. The proposed fractal-based monitoring framework can be integrated into existing SCADA systems to enhance continuous operational control and support timely decision-making. This method is particularly suitable for complementing conventional inspection techniques by providing an additional layer of real-time monitoring between scheduled inspection intervals.

Keywords: biodiesel; diesel; transesterification; triglyceride; grape seed.

Date submitted: 10.09.2025     Date accepted: 19.11.2025     Date published: 22.05.2026

References

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This study presents an enhanced decision‑support framework for subsea pipeline risk management by integrating economic risk parameters into an existing hybrid model that combines Fuzzy Analytic Hierarchy Process (Fuzzy AHP), the Similarity Aggregation Method (SAM), Bayesian probability updating, and Monte Carlo-based uncertainty analysis. Alongside conventional environmental, design, structural, and operational factors, the revised methodology explicitly incorporates economic consequences such as repair costs, production interruptions, environmental penalties, and life‑cycle cost variability. Environmental considerations include hydrostatic pressure, seabed characteristics, seawater temperature, currents, sediment transport, and corrosive exposure, while technical parameters align with established offshore pipeline standards. Bayesian updating and fuzzy logic support the evaluation of posterior risk probabilities, whereas Monte Carlo simulation enables the propagation of uncertainty related to economic loss estimations under multiple failure scenarios. As a result, the improved framework generates risk indices that reflect both operational vulnerabilities and financial exposure, thereby supporting more realistic, risk‑informed decision‑making for offshore pipeline systems. Although technical risk parameters are quantified through structured evaluation, the economic risk dimension is developed through a classification‑ and synthesis‑based approach rather than project‑specific financial data. Economic indicators are formulated as relative, decision‑oriented constructs using normalization, comparative scaling, and prioritization of dominant contributors. This avoids dependence on absolute monetary values, enhances generalizability, and ensures consistent integration of economic considerations into the fuzzy AHP-SAM framework. By embedding economic consequences within the technical risk structure, the proposed methodology advances traditional risk assessment into a cost‑aware decision‑support system, enabling stakeholders to identify risks with moderate technical likelihood but disproportionately high economic impact.

Keywords: Bayes' theorem; fuzzy logic; similarity aggregation method; posterior probability; economic risk; life-cycle cost.

Date submitted: 21.01.2026     Date accepted: 06.04.2026     Date published: 25.05.2026

References

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In this research work, the preparation of an environmentally friendly, internationally compliant bio-component diesel fuel with minimal impact on engine performance and the study of its physicochemical properties were carried out. Fuel oil was hydrocracked at a temperature of 430 °C and a pressure of 4.0 MPa in the presence of a zeolite catalyst, yielding 60.0 wt.% diesel fraction. Grape seed oil was extracted by the cold-pressing method and transesterified with methanol at 65 °C for 120 minutes in the presence of Aydag zeolite as a heterogeneous catalyst, resulting in the synthesis of 92.9 wt.% fatty acid methyl esters (biodiesel). Infrared spectroscopic analysis confirmed the presence of carbonyl (C=O) and ester (C–O) functional groups in the biodiesel. The obtained biodiesel was blended with diesel fuel at volume ratios of 20, 40 and 60 % to prepare B20, B40 and B60 compositions. Key physicochemical properties of the fuels, including density, kinematic and dynamic viscosity, flash point, cetane number, and lubricity, were determined and compared with the requirements of PN-EN 590:2022 and PN-EN 14214+A2:2019-05 standards. It was found that the addition of biodiesel to the diesel fraction leads to a linear increase in density, viscosity, flash point, and cetane number. The cetane number of biodiesel (54.9) was higher than that of conventional diesel fuel, and an 8.93% increase in the cetane number was observed in the B60 composition. The addition of biodiesel to diesel fuel at 20-60 % (by volume) ensures technical compatibility and environmental advantages, making it a viable alternative for the energy- efficient utilization of agro-industrial waste. 

Keywords: biodiesel; diesel; transesterification; triglyceride; grape seed.

Date submitted: 24.11.2025     Date accepted: 14.04.2026    Date published: 25.05.2026

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In this research, symmetric and asymmetric aliphatic esters based on 1,1,1-trimethylolpropane (TMP) were synthesized with high yields using caproic and pelargonic acids. The synthesized compounds - TMP tricaproate (N1), TMP tripelargonate (N2), and the asymmetric dicaproate-pelargonate ester (N3) - were rigorously characterized using FT-IR and NMR (1H and 13C) spectroscopy. A comprehensive study was conducted to evaluate their physicochemical properties, viscosity-temperature characteristics, and biological activities. Experimental results demonstrated that increasing the carbon chain length leads to higher kinematic viscosity and a decrease in density; specifically, sample N2 exhibited the highest viscosity, while the asymmetric N3 ester showed a superior viscosity index of 168. These balanced tribological properties suggest that these esters are highly suitable as base stocks for high-performance, low-viscosity aviation lubricants. Furthermore, the bactericidal efficiency of the esters was evaluated against sulfate-reducing bacteria (SRB). At concentrations ranging from 25 to 100 mg/L, the compounds achieved a corrosion protection effect of 96.9-100 %, significantly outperforming standard industrial reagents. Theoretical investigations were performed using Density Functional Theory (DFT) at the B3LYP/6-31G(d,p) level to calculate HOMO (Highest Occupied Molecular Orbital) - LUMO (Lowest Unoccupied Molecular Orbital) orbitals and various quantumchemical descriptors (ionization potential, electrophilicity index, chemical hardness, etc.). The substantial energy gaps (7.390-7.575 eV) confirm the high thermal and oxidative stability of these molecules. These theoretical findings strongly correlate with experimental data, providing a robust scientific framework for utilizing these TMP esters as next-generation lubricant components and effective multifunctional bactericidal inhibitors.

Keywords: trimethylolpropane; esters; lubricants; bactericidal activity; DFT calculations; quantum-chemical descriptors.

Date submitted: 15.09.2025     Date accepted: 04.05.2026     Date published: 01.06.2026

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