Study On The Flow Law Of Gas-liquid Two-phase In An Internal Vortex Tool In Horizontal Gas Well

The continuous exploitation of gas reservoirs leads to the shortage of formation energy and the invasion of bottom and edge water,forming gas well loading.The liquid loading seriously affects the recovery rate of natural gas,so it is urgent to adopt effective drainage gas recovery measures to stabilize the production of gas well with liquid loading.Horizontal wells can increase the deflating area,the production of per well and the economic efficiency,and has become a hot development mode of gas wells.With the wide application of horizontal gas wells,the liquid loading in horizontal gas wells is inevitable.At present,it is known that a large area of horizontal well has emerged water in domestic gas fields such as Danu gas field and Xushen gas field.A variety of drainage gas recovery technologies for vertical wells have been developed in many years of development practice at home and abroad,but most drainage gas recovery technologies which has good effects in vertical wells are not suitable for horizontal wells.So it is necessary to develop and promote the drainage gas recovery technology to solve the liquid loading in horizontal gas wells.In order to predict the liquid unloading accurately and take effective measures to the gas well,it is necessary to calculate the critical carrying velocity.In this paper,considered the mechanism of liquid flim entrainment droplet,in combination with the process of shear disturbance wave was broken into droplets,a new critical carrying model was built.The effect of the liquid producing,liquid phase components,gas phase components,tubing diameter and temperature on the critical carrying velocity was discussed.At the same time,the classical model and the new model were used to judge the liquid loading,and the accuracy of the model was verified.An internal vortex tool was proposed in this paper for drainage gas recovery for horizontal gas well borrowing from the idea on vertical wells.Numerical simulation method was used to study the flow law of gas-liquid two-phase of the internal vortex tool in horizontal well,and explained the drainage mechanism of the tool.The results showed that when the gas-liquid two-phase flowed through the spiral line of the tool,the gas-liquid two-phase flow was induced by the spiral line.Due to the density difference between the gas phase and liquid phase,most of the liquid was thrown to the wall of the wellbore under the action of inertia force,while the gas phase spined at high speed in the center of the wellbore.At this time,the irregular mixed flow of gas-liquid two-phase was converted into the spiral laminar flow which the liquid flow area significantly reduced.This flow state can reduce the slip loss between the two phase and the friction resistance between the fluid and the wall,so the gas well drainage can be completed by using its own energy.On this basis,the influence of the structure parameters of the internal vortex tool on drainage effect was investigated,and the optimized structure parameters of the tool were given.Based on the moment of momentum theorem,the tangential velocity,local resistance coefficient and the swirl number decay model were established,and the decay law of the two-phase free swirling flow after the tool was studied.Calculation results showed that at the same length to diameter ratio of the tool,the free swirling flow,the decay of free swirl was slower than that of local resistance coefficient.It proved that the free swirl after the tool can maintain a distance,and the energy loss in process of gas carrying liquid can be reduced because of the swirl maintenance,which undoubtedly played an important role in conserving gas well energy and improving gas well drainage efficiency.Finally,the numerical simulation results of the drainage effect of the internal vortex tool were verified by the laboratory experiment.The flow state and pressure variation rules of the tool in the laboratory experiment were consistent with those of the numerical simulation,and it was proved that the internal vortex tool could improve the drainage capacity of the horizontal gas well and solve liquid loading in the horizontal gas well.