# Study on Flow Characteristics of Venturi Accelerated Vortex Drainage Tool in Horizontal Gas Well
## 4 Results and Discussion
### Pressure Drop with Different Gas Flow Rates  
When the liquid flow rate is 3 L/min and the gas flow rate is 100-600 m\({}^{3}\)/h, the instantaneous pressure drop in the horizontal tube (\(P_{1}\)-\(P_{2}\)) was measured by conducting different experiments with the tube drainage, the vortex tool, and the venturi and vortex tool, as shown in Figure 8.  
Analyzing the changes in instantaneous pressure drop in Figure 8, it is evident that as the gas flow rate increases, the vacuum level used by the venturi accelerated vortex tool is significantly higher, in striking contrast to using the vortex tool alone. Therefore, the venturi accelerated vortex tool induces the negative pressure drop to increase downstream in the horizontal tube, resulting in a more stable spiral flow. Hence, the length of the spiral flow is extended, and the liquid-carrying performance is effectively enhanced. The fluctuations of the pressure drop gradually decreased with the increase in the gas flow rate, and the instantaneous pressure drop became more stable.  
According to the above-mentioned analysis, the pressure drop in the horizontal tube was averaged, as shown in Figure 9, and the total pressure drop in the horizontal and vertical tube (\(P_{1}\)-\(P_{3}\)) was averaged, as shown in Figure 10.  
Figure 8: Instantaneous pressure drop of different tools in the horizontal tube with liquid flow rate of 3 L/min and gas flow rates of 100-600 m\({}^{3}\)/h. (Supplementary Figure S1).  
Figure 7: Spiral flow patterns for the venturi and vortex tool, with liquid flow rate of 3 L/min and gas flow rates of 100 m\({}^{3}\)/h to 600 m\({}^{3}\)/h.  
Figure 9 illustrates that the average negative pressure drop generated by the venturi accelerated vortex tool is the highest among the three tools, followed by that of the vortex tool. On the contrary, the average negative pressure drop generated by the tube drainage is the lowest. As the gas flow rate increases, the average negative pressure drop is also increased. The increase in the negative pressure drop becomes more significant with the application of higher gas flow rates. This result indicates that the increase in gas flow rate is beneficial for drainage, and the venturi accelerated vortex tool can further improve the liquid-carrying performance.  
Figure 10 explains the average total pressure drop in both the horizontal and vertical tubes. When the vortex tool was used, the total pressure drop increased at low gas flow rates (<200 m\({}^{3}\)/h). The main reason is that under low gas flow conditions, the liquid for the tube drainage first forms a stable stratified flow, while the liquid for the vortex tool and the venturi accelerated vortex tool forms an unstable spiral laminar flow. The unstable spiral laminar flow in the vortex tools increased the total pressure  
Therefore, the venturi accelerated vortex tool results in smaller total pressure loss. When the gas flow rate increased to 300 m\({}^{3}\)/h, the liquid in the tube drainage formed an unstable stratified flow, resulting in an increasing pressure drop. As the gas flow rate continued to increase, the annular flow and fog flow were gradually formed, which induced a reduction in the pressure drop for the tube drainage. However, these were still higher than for the other two vortex tools.