World experience shows that important factor in the calculations for natural gas consumption between suppliers and consumers is not only the volume of natural gas, but the quality indicators. With gas market liberalization, gas properties are expected to vary more frequently and strongly (composition, heating value etc.). Quality of natural gas is currently a topical issue, considering the steady increase of gas consumption in the world in recent decades. Existent chromatographs and calorimeters are very accurate in gas quality determination, but general expenditure and maintenance costs are still considerable. Market demands alternative lower cost methods of natural gas quality determination for transparent energy billing and technological process control.Investigation results indicate that heating value (HV) is a nonlinear function of such parameters as sound velocity in gas, N2 and CO2 concentration. Those parameters show strong correlation with natural gas properties of interest (HV, density, Wobbe index), during analysis conducted on natural gas sample database. For solving nonlinear multivariable approximation task of HV determination, artificial neural networks were used. Proposed approach allowed excluding N2 concentration from input parameters with maintenance of sufficient accuracy of HV determination equal to 3.7% (with consideration of N2 concentration -2.4%) on sample database. For validating of received results corresponding experimental investigation was conducted with reference analysis of physical and chemical parameters of natural gas samples by gas chromatography and followed superior HV calculation according to ISO 6976:1995. Developed experimental setup consist of measuring chamber with ultrasonic transducer, reflector, pressure, temperature and humidity sensors, ultrasonic inspection equipment for sound velocity measurements and CO2 concentration sensor with relevant instrument. The experimental setup allows measurement of sound velocity at 1MHz frequency and CO2 concentration in natural gas sample along with parameters control (temperature, humidity, pressure). The HV calculation algorithm was based on specially designed and trained artificial neural networks.Experimental investigation of proposed approach was conducted on 40 real samples of locally distributed natural gas. Obtained results, in comparison to reference values, showed absolute error in Lower HV (net calorific value) determination equal 166 kJ/m 3 , while relative error was equal 4.66%. Developed technology allows construction of autonomous instrument for instant natural gas quality determination, which can be combined with volume meters in order to provide transparent energy flow measurement and billing for gas consumers. Additionally it can be used for gas sensitive technological process control.

The purpose of this work is to ensuring the strength of main gas pipelines bends by studying the peculiarities of single-phase and multiphase flows movement through the internal cavity, the processes of erosion wear and the wall stress state. The problem of synergistic influence of gas-dynamic processes (uneven pressure distribution in the internal cavity), temperature difference and erosion wear on the stress state of the bends of main gas pipelines was solved by numerical simulation. Based on the results of simulation the processes of bends erosion wear, an algorithm for three-dimensional simulation of bend walls erosion defects was developed. The complex three-dimensional geometric shape of the erosion defects of the bend wall varied according to the rate of erosion wear process. This algorithm made it possible to determine the regularities for the influence of the bend erosion defects magnitude on bends stress state. It was established that considering the maximum depth of bend erosion defects 9.6 mm, 10.5 mm and 11.9 mm, the equivalent stresses in the deepest places of the erosion defect were greater than on the concave side of the bend and in straight sections of the pipeline.

Purpose: The purpose of this work is to consider the complications that arise while operating gas condensate wells, in particular, the accumulation of hydrocarbon condensate, formation and condensation water at wells and flowlines, to develop a method for removing liquid from wells and flowlines before it entering a gas treatment unit and being treated with surfactants and to develop a method for the foam destruction in the gas-liquid flow. Design/methodology/approach: The operational parameters of gas-condensate wells of the Yuliivske oil and gas condensate field (OGCF) have been analysed. Wells have been identified that are operated in difficult conditions due to the accumulation of the liquid at the bottom hole and in flowlines. The volume of the liquid accumulated at the bottom hole of gas condensate wells is estimated. The quantity of surfactants, the volume and concentration of the solution required to remove the liquid were calculated individually for each well. The program of experimental researches has been made. The efficiency of the application of surfactant solution was experimentally determined and a positive result was achieved in the form of an increase in production by 10%. A new approach to the use of surfactant solution, as well as the foam destruction, has been proposed. The studies were performed within the framework of research and development work by the specialists of the Ukrainian Scientific Research Institute of Natural Gases. Findings: Comprehensive measures are proposed to increase the efficiency of gas condensate wells operation. They are monitoring of operational parameters of wells by pressure and temperature gauges installed at the wellhead and at the inlet gas pipelines of the gas treatment unit; calculation of the volume of accumulated fluid in the wellbore and flowline; installation of a complex of automated feeding a surfactant solution of both in the annulus of the wells and in the flowline. For this purpose, two options for the complex and arrangement are proposed. The proposed options involve the use of various equipment and have a different principle of operation. To prevent foam from entering the gas treatment unit, a method of its destruction has been proposed. The implementation of the proposed comprehensive measures will allow controlling the well operation mode, timely liquid removal from the well and the flowline and ensure stable hydrocarbon production. Research limitations/implications: The obtained results of laboratory and experimental studies have shown that using a surfactant solution is reasonable to remove the liquid from gas condensate wells. To increase the efficiency of the measure, a new method of feeding surfactant solution was developed by installing a unit for automated feeding (UAF) of a surfactant solution at the mouth. Practical implications: The results of laboratory tests allow using a surfactant solution reasonably in order to remove the liquid from gas condensate wells, as well as possible further destruction of foam in the gas-liquid flow for increasing both the efficiency of the extraction and production volume. Originality/value: On the basis of previously performed experimental research, it has been established that it is advisable to use a surfactant solution to remove the liquid from gas condensate wells and flowlines. A new method of removing liquid from gas condensate wells and flowlines has been developed, as well as a method of destroying foam in a gas-liquid flow, which are original and can be implemented.

Ukraine ranks first in the world in terms of energy intensity per unit of GDP, which means that Ukrainian enterprises spend the most energy in comparison with other countries in the production of the unit of production. The Gas Transportation System (GTS) is no exception. Gas transit is expected to reduce from 2020 due to the construction of gas pipelines bypassing the territory of Ukraine, which will lead to a decrease in the profitability of the GTS and, if not sufficiently loaded, to its loss. That is why ensur ing efficient operation of the GTS equipment in terms of energy efficiency is becoming more relevant today than ever.Purpose. To develop methods for enhancing the energy efficiency of the gas transmission system of Ukraine (based on the analysis of the gas distribution stations (GDS) operation) without significant investment, considering the possible decrease in gas transmission.Methodology. In the work, the analysis of scientific and technical literature and regulatory documents is performed; mathemat ical modelling and analysis of operational performance of GDS is performed to determine the economic and environmental effect of the proposed measures.findings. It was confirmed that adjusting gas pressure at the outlet to the design pressure is a promising direction for energy efficiency increasing. According to the analysis of scientific and technical literature and regulatory documents, the optimal gas temperature at the outlet of the gas distribution system was determined. It was outlined that the implementation of the developed set of measures will allow obtaining a significant economic and environmental effect.originality. The necessity of implementation of a set of costfree measures was developed and justified, mainly, reduction of the present natural gas indicators of temperature and pressure at the outlet of the gas distribution stations to the optimal ones, which will increase energy efficiency and ecological efficiency of its operation.Practical value. The results will be used for production activity purposes, during the operation of gas distribution stations

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