# Study on Flow Characteristics of Venturi Accelerated Vortex Drainage Tool in Horizontal Gas Well
## 1 Introduction
They established equations for the axial and radial movement of droplets and the calculation formula for the optimal helix angle of the vortex tool, validating the reliability of the optimal helix angle calculation formula. [PERSON] et al. [8] conducted two-phase vortex flow experiments in the wellbore, studying the impact of the structural parameters of the vortex tool on drainage effectiveness. The results indicated that enhancing the sealing on both sides of the flow channel and reducing the flow channel size can improve the effectiveness of the vortex tool. [PERSON] et al. [9] established models for the gas-liquid separation efficiency and the pressure loss of the vortex tool, studying the impact of structural parameters on the liquid-carrying performance and the pressure loss of the vortex tool. They improved the vortex tool based on the research results. The field test results showed that the optimized vortex tool is beneficial for increasing gas well production. [PERSON] et al. [10], by numerical simulation and theoretical calculation, studied the separation efficiency of two-phase flow in a double-helix separator. The results showed that the separation efficiency of the helical separator increased with the increase in the gas-liquid ratio and overall gas-liquid flow rate. Under certain conditions of helix number and gas-liquid ratio, there exists an optimal pitch. [PERSON] et al. [11] used an orthogonal experimental method to systematically study the attenuation characteristics, effective swirl length, and various other factors affecting the decay of vertical pipe swirl. The authors obtained the relationship between the initial swirl intensity and the decay rate of swirl intensity, proposed a comprehensive decay model for the swirl intensity, and established an evaluation method of the effective vortex length. The goal was to determine the optimal structure of the vortex tool in typical gas wells. In another interesting work, [PERSON] et al. [12] designed a vortex tool and conducted computational fluid dynamics analysis of its drainage and gas extraction efficiency in horizontal wells to optimize its structure. The results indicated that the vortex tool can increase the gas phase velocity and achieve gas-liquid separation. [PERSON] et al. [13] attempted to reveal the regularity of the critical gas velocity in the swirl field generated by the vortex tool. The authors established a model for calculating the critical gas velocity in vortex drainage wells. The analysis included the impact of the helix angle and the vortex tool hub diameter on the magnitude of the reduction in critical gas velocity. The experimental validation demonstrated that the model can predict the critical gas velocity under different production conditions with different vortex tools. The critical gas velocity increases with the increase in the helix angle and decreases with the increase in the hub diameter. [PERSON] et al. [14] conducted experiments to study the gas-liquid flow pattern and pressure drop when the vortex tool was inserted into the tube with accumulated liquid at the well bottom and compared it with a regular tube. The impacts of the structural parameters and the stages of the vortex tool on pressure drop were examined. From the acquired experimental results, it was indicated that the insertion of the vortex tool is advantageous for an earlier transition to the circumferential flow, and the induced vortex can suppress liquid fallback. The helix angle of the spiral guide plate has a more significant effect on the pressure drop than its length. By changing the helix angle, the total pressure drop and downstream pressure gradient are significantly reduced, even below that of a regular tube. CFD numerical simulations have also been deployed to study the gas-liquid two-phase flow and highlight the impact of production parameters and tool structures on the performance of vortex drainage [15; 16; 17].