Numerical Study On Gas-Liquid Two-Phase Swirling Flow Characteristic In Gas Wellbore With Vortex Downhole Tool

With the deepening of the development process,part of the natural gas field in our country has entered into the phase of middle and later exploitation,a large number of water wells for the low yield need increase the amount of gas liquid carrying purposes to decrease the downhole fluid.Vortex drainage gas technology can effectively solve the problem,it is an important way to improve the recovery of low-yield wells and reduce the cost of mining.The application background of this paper is technology of recovery gas by discharge wate in gas wellbore.by using the Computational Fluid Dynamics software ANSYS.This paper calculate gas-liquid two-phase swirling flow characteristic in gas wellbore by numerical simulation,obtain the effects of swirl on transition of flow pattern,distribution of gas and liquid phases,gas-liquid interface behavior,velocity field and swirl decay,investigate the process of the formation and development of secondary flow characteristics,and analyze the formation mechanism of the annular liquid film adherent.The results show that mist flow is transformed to annular flow under the effect of helical tape.Swirl of gas is weak,forming a central core in the form of gas and flowing upward rapidly;Swirl of liquid is strong,forming an annular liquid film along the wall and flowing upward.It reduces gas entrainment critical flow rate and flow pressure within the wellbore,and improves the liquid carrying capacity.By swirl flow field analysis,the results show that: secondary vortices appear in the helical tape region,these vortices develop and their structures change,the liquid film is not continuous along circumferential direction of the pipe due to non-uniform centrifugal force.Away from the helical tape,fluid flows helically without secondary vortices,droplets and liquid film distribution become uniform.Gas tangential velocity value is high away from the swirling center and low near the pipe center,there is an offset between swirling center and pipe center.On the basis of orthogonal design method,this paper analyze nine different structural parameters of vortex downhole tools(spiral plate diameter,thickness of the guide vanes,blade pitch)through the numerical simulation method,investigate the influence of Swirl attenuation and the pressure drop,optimize the vortex structure dimensions.Finally there choosed one kind of vortex structure dimensions: blade pitch S=100mm,blade thickness δ=8mm,center column diameter d=38mm,and verify this tool by the calculation of swirl characteristic and pressure drop.The research results reveal swirl drag cleanup mechanism vortex gas underground drainage and gas,providing technical support and theoretical basis for our vortex gas drainage technologies and design tools vortex structure optimization.