# Study on Flow Characteristics of Venturi Accelerated Vortex Drainage Tool in Horizontal Gas Well
## 1 Introduction
The underlying mechanism of the vortex downhole tool to improve production efficiency and the geometric parameter optimization method have been numerically investigated, suggesting that the vortex downhole tool can reduce the flow pressure drop [18]. New eddy current tools that are different from traditional structures have also been designed [19]. [PERSON] et al. [20], for large pressure loss and short effective distance of traditional vortex tools in gas wells, designed and installed the organic combination of jet vortex drainage and gas production tools. The gas-liquid mixture before and after the jet vortex tool was analyzed, and the flow trajectory, the pressure loss, and the liquid volume fraction change were investigated. The comprehensive influence of each structural parameter on the effective working distance was optimized, and the optimal structural parameters of the jet vortex tool were obtained. The results showed that the critical liquid-carrying flow rate and pressure loss were reduced by using the jet vortex tool, whereas the axial velocity, initial velocity of gas phase and liquid phase, and the effective flow distance increased. As a result, the liquid-carrying capacity of gas wells was significantly improved. [PERSON] et al. [21] proposed a new type of vortex drainage solution that combined self-excited oscillating pulsed jet and swirling flow. On the basis of theoretical analysis and experimental research, the numerical simulation results were compared with the drainage performance of conventional swirling tools. The results indicated that the new swirl tool can improve the liquid-carrying capacity of gas wells by changing the flow pattern of the gas-liquid medium without increasing energy consumption. Based on the Coanda effect, [PERSON] et al. [22] established a numerical model of the double-vortex anti-friction tool. At the same time, the authors studied the influence of different geometric parameters on the vibration characteristics of the double-vortex anti-friction tool. The results showed that the double-vortex anti-friction tool can produce larger pressure drop and vibration frequency, and the pressure drop change process is more stable and has a better anti-friction effect. The change in the geometric parameters of the double-vortex anti-friction tool not only affects the pressure drop and the oscillation frequency but also the pressure drop. In summary, many vortex tools for drainage in gas wells have been developed in the literature. However, the combination of the venturi acceleration tools and vortex tools for drainage and gas recovery has been scarcely examined. In particular, a deep understanding of the evaluation and analysis of swirl length is required. To effectively address this issue,in this work, the venturi accelerated vortex tool of the horizontal gas well was designed and the multiphase flow experimental device of the horizontal well was set up. The horizontal well drainage and gas recovery experiments for the tube drainage, the vortex tool, and the venturi accelerated vortex tool were carried out. Additionally, the drainage effect of the venturi accelerated vortex tool was evaluated. The impact of the different gas and liquid flow rates on swirl length and pressure drop were thoroughly analyzed. The mechanism of venturi accelerated vortex tool drainage was determined, which can provide guidance for the future applications of vortex tools.