Study On Gas-Liquid Two-Phase Flow Characteristics And Application Of Turbulent Sealed Gas-Lift Plunger

With the proposal of the "dual carbon" goal,the global demand for clean energy is becoming increasingly urgent,resulting in a huge supply and demand gap in the natural gas market.However,liquid loading in gas wells has always been a challenge faced by natural gas extraction,especially for directional well gas production,which has not yet formed an efficient mining process.The existing processes have problems such as excessive equipment,high investment,and environmental pollution.Therefore,from the perspective of energy conservation and emission reduction,it is imperative to form an economically effective,simple and feasible directional gas well mining technology.Gas lift plunger is an effective mining method to solve the problem of liquid loading in gas wells.Currently,there is a basic process plan in vertical wells,however,there are no efficient and reliable mining schemes for directional Wells in China,and there is a lack of understanding of the operating status and flow field characteristics of the plunger in gas wells.How to apply numerical methods to deeply study the influence of gas lift plunger structure on flow field changes and the impact of well inclination on its working performance,and improve the stability and reliability of gas lift plunger has very important theoretical and engineering practical significance.This article proposed a numerical calculation model suitable for the flow field of gas lift plunger,and conducted relevant numerical simulation and experimental research.Taking the gas lift plunger suitable for directional wells as the research object,based on the gas compressibility theory,the gas-liquid two-phase flow was calculated using the VOF model,the fluid control equation was closed using the Reynolds stress turbulence model,the calculation method of the turbulence control equation in the fluid domain was established,and the calculation model of the gas lift plunger was realized.Numerical simulation studies were conducted on five types of sealing groove structures,and the differences in flow fields and distribution characteristics of flow fields were obtained for different groove types.The reliability of the established numerical model was verified through indoor experimental testing and analysis.Three factors and five levels of orthogonal experimental numerical simulation analysis were conducted,among which the groove factor was a highly significant factor.The order of the influence of groove on sealing performance was arc shape>rectangle>right angle trapezoid>reverse right angle trapezoid>isosceles trapezoid.The optimal structural parameters of the plunger sealing groove were selected,namely,the groove shape was arc shape,the groove width was 14 mm,and the groove depth was 7mm.In order to reduce eccentric wear and improve sealing performance in directional wells,a jet hole structure was added on the basis of the optimized optimal plunger sealing groove structure.Numerical simulation analysis was conducted on the overall performance of the plunger,clarifying that the working principle of the rotary plunger is to limit the liquid sliding on the upper part of the plunger through the rotating jet.The analysis of the impact of different gas production rates,casing pressures,well inclination angles,and motion parameters on the flow field and sealing performance of the gas lift plunger was completed,further clarifying the comprehensive working performance of the rotary plunger.Based on indoor experiments,the sealing performance,motion characteristics,and working performance of the groove were tested at different well angles.The reliability of the numerical model and calculation method was verified by comparing the measured results with the numerical simulation results.On this basis,engineering application testing and analysis were conducted,and a transient optimization model for the working system of directional well plungers was established using the coupling concept of wellbore and near wellbore formation.Based on laboratory testing results,parameter modifications were made to the optimization model,and case studies of system optimization for two directional gas wells were conducted.The on-site implementation results show that the developed plunger structure can achieve a periodic gas lift process,reduce bottom hole backpressure,and significantly increase production by over 60%.The research results indicate that the numerical calculation model established for the gas lift plunger is reasonable,and the proposed plunger structure can achieve efficient production of directional gas wells.