The research was performed in order to obtain the physical picture of the movement of condensed droplets and solid particles in the flow of natural gas in elbows and T-junctions of the linear part of the main gas pipeline. 3D modeling of the elbow and T-junction was performed in the linear part of the gas main, in particular, in places where a complex movement of multiphase flows occurs and changes its direction. In these places also occur swirls, collisions of discrete phases in the pipeline wall, and erosive wear of the pipe wall. Based on Lagrangian approach (Discrete Phase Model – DPM), methods of computer modeling were developed to simulate multiphase flow movement in the elbow and T-junction of the linear part of the gas main using software package ANSYS Fluent R17.0 Academic. The mathematical model is based on solving the Navier–Stokes equations, and the equations of continuity and discrete phase movement closed with Launder–Sharma (k–e) two-parameter turbulence model with appropriate initial and boundary conditions. In T-junction, we simulated gas movement in the run-pipe, and the passage of the part of flow into the branch. The simulation results were visualized in postprocessor ANSYS Fluent R17.0 Academic and ANSYS CFD-Post R17.0 Academic by building trajectories of the motion of condensed droplets and solid particles in the elbow and T-junction of the linear part of the gas main in the flow of natural gas. The trajectories were painted in colors that match the velocity and diameter of droplets and particles according to the scale of values. After studying the trajectories of discrete phases, the locations of their heavy collision with the pipeline walls were found, as well as the places of turbulence of condensed droplets and solid particles. The velocity of liquid and solid particles was determined, and the impact angles, diameters of condensed droplets and solid particles in the place of collision were found. Such results provide possibilities for a full and comprehensive investigation of erosive wear of the elbow and T-junction of the linear part of the gas main and adjacent sections of the pipeline, and for the assessment of their strength and residual life.

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.

Purpose: The purposes of the article are to determine the hydraulic efficiency of two gas gathering pipelines of the Yuliivskyi oil and gas condensate production facility (OGCPF) and develop a set of measures to increase it; to experimentally determine the efficiency of using foams to increase the hydraulic characteristics of the gas gathering pipelines in the Yuliivskyi OGCPF; to develop a set of measures that will help to improve the hydraulic characteristics of gas gathering pipelines. Design/methodology/approach: The research methodology consists in determining the hydraulic efficiency of gas gathering pipelines before and after cleaning their inner cavity with foams with different expansion ratios and comparing the obtained values, which allows to objectively assess the efficiency of this cleaning method. 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: The pilot testing was carried out to determine the efficiency of cleaning the inner cavity of gas gathering pipelines with foams with different expansion ratios. It showed positive results. It was determined that cleaning the inner cavity of gas gathering pipelines with foams with the expansion ratio from 80 to 90 led to an increase in the hydraulic efficiency coefficient by 10.5%, and with foams with the expansion ratio from 50 to 60 – by 5.7%. The measures taken to clean the inner cavity of gas gathering pipelines from liquid contaminations have proven their efficiency and can be recommended for other fields. Research limitations/implications: The obtained results show that it is reasonable to conduct the experimental studies on the efficiency of cleaning the inner cavity of gas gathering pipelines with the foams with higher expansion ratios. To achieve the maximum quality of cleaning the gas gathering pipelines, it is necessary to develop a new method that will combine the use of foam and gel piston.Practical implications: The performed experimental studies help to take a more reasonable approach to cleaning the inner cavity of gas gathering pipelines with foams and to predict in advance the effect of the foam expansion ratio on the hydraulic efficiency of gas gathering pipelines. Originality/value: The experimental studies on the effect of foam expansion ratios on the hydraulic efficiency of gas gathering pipelines are original.

Purpose: The article implies theoretical and experimental studies of the liquid pollution accumulations impact on the efficiency of gathering gas pipelines operation at the Yuliivskyi oil and gas condensate production facility (OGCPF). Research of efficiency of gas pipelines cleaning by various methods. Design/methodology/approach: The research methodology consists of determining the hydraulic efficiency of gathering gas pipelines before and after cleaning of their internal cavity by different methods and comparing the obtained results, which allows to objectively evaluate the efficiency of any cleaning method. CFD simulation of gas-dynamic processes in low sections of gas pipelines with liquid contaminants. Findings: Experimental studies of cleaning efficiency in the inner cavity of the gas gathering pipelines of the Yuliivskyi OGCPF by various methods, including: supply of surfactant solution, creating a high-speed gas flow, use of foam pistons were performed. It was established that cleaning the inner cavity of gas gathering pipelines by supplying a surfactant solution leads to an increase in the coefficient of hydraulic efficiency by 2%-4.5%, creating a high-speed gas flow by 4%-7%, and under certain conditions by 8%-10 % and more. However, for two gas pipelines the use of foam pistons allowed to increase the coefficient of hydraulic efficiency from 5.7 % to 10.5 % with a multiplicity of foam from 50 to 90. be recommended for other deposits.The results of CFD simulation showed that the accumulation of liquid contaminants in the lowered sections of gas pipelines affects gas-dynamic processes and leads to pressure losses above the values provided by the technological regime. With the increase in liquid contaminants volume the pressure losses occur. Moreover, with a small amount of contamination (up to 0.006 m3), liquid contaminants do not have a significant effect on pressure loss. If the contaminants volume in the lowered section of the pipeline is greater than the specified value, the pressure loss increases by parabolic dependence. The increase in mass flow leads to an increase in the value of pressure loss at the site of liquid contamination. Moreover, the greater the mass flow, the greater the impact of its changes on the pressure loss. The CFD simulation performed made it possible not only to determine the patterns of pressure loss in places of liquid contaminants accumulation in the inner cavity of gas pipelines, but also to understand the gas-dynamic processes in such places, which is an unconditional advantage of this method over experimental. Research limitations/implications: The obtained simulation results showed that the increase in the volume of liquid contaminants in the inner cavity of gas gathering pipelines leads to an increase in pressure losses above the value provided by the technological regime. To achieve maximum cleaning of gas gathering pipelines, it is necessary to develop a new method that will combine the considered. Practical implications: The performed experimental results make it possible to take a more thorough approach to cleaning the inner cavity of gas gathering pipelines and to forecast in advance to what extent the hydraulic efficiency of gas gathering pipelines can be increased. Originality/value: The obtained results of CFD simulation of gas-dynamic processes in lowered sections of gas pipelines with liquid contaminants, experimental studies of the effectiveness of various methods of cleaning the inner cavity of gas gathering pipelines has original value.