# Study on Flow Characteristics of Venturi Accelerated Vortex Drainage Tool in Horizontal Gas Well
## 4 Results and Discussion  
### The Liquid-Carrying Capacity with Different Gas Flow Rates  
The drainage experiments of the horizontal tube were carried out using the three kinds of tube drainage, the vortex tool, and the venturi accelerated vortex tool. To compare the drainage performance of the different tool structures, a liquid flow rate of 3 L/min and a gas flow rate ranging from 100 m\({}^{3}\)/h to 600 m\({}^{3}\)/h were used, and the acquired results were thoroughly investigated. The flow pattern of the horizontal tube was photographed as the gas-liquid mixture flowed through the different tools. The captured spiral flow patterns are displayed in Figure 5.  
As shown in Figure 5, when the liquid flow rate is 3 L/min and the gas flow rate is 100 m\({}^{3}\)/h, the gas-liquid mixture flows in a typical layered flow pattern using the tube drainage. It is interesting to notice that no obvious spiral flow is formed using the vortex tool, and the short spiral flow is formed at the tool's outlet using the venturi accelerated vortex tool. Additionally, the flow shows a trend of transitioning from layered flow to spiral flow downstream. When the gas flow rate is increased to 200 m\({}^{3}\)/h, spiral flow also occurs with the vortex tool. The spiral flow is clearer for the venturi accelerated vortex tool, and the length of spiral flow is slightly longer. However, after flowing a certain distance the flow essentially returns to laminar flow. As the gas flow rate continues to increase, the length of the spiral flow significantly increases. It can be clearly observed that the spiral flow produced by the venturi accelerated vortex tool is significantly longer than that of the other tool. When the gas flow rate reaches 600 m\({}^{3}\)/h, a stable spiral flow is formed. The spiral flow fills the horizontal observation tube (the length is 2 m) with the vortex and venturi accelerated vortex tool. Nevertheless, the flow is dispersed turbulent flow with the tube drainage. This effect indicates that the vortex tool can effectively separate gas and  
Figure 4: Multiphase flow experiment device physical diagram. \begin{table}
\begin{tabular}{c c} \hline
**Experimental Conditions** & **Specific Parameters** \\ \hline Temperature (\({}^{\circ}\)C) & 20–25 \\ Liquid flow rate (L/min) & 1, 3, 5, 10, 15 \\ Gas flow rate (m\({}^{3}\)/h) & 100, 200, 300, 400, 500, 600 \\ Liquid Reynolds number & 420, 1260, 2101, 4202, 6303 \\ Gas Reynolds number \(\times\) 10\({}^{5}\) & 0.51, 1.02, 1.53, 2.04, 2.55, 3.06 \\ \hline \end{tabular}
\end{table} 
Table 3: Experimental parameters of drainage in horizontal gas wells. liquid, transforming the mixed gas-liquid turbulent flow into a laminar spiral flow. The measured length of the spiral flow is shown in Figure 6. As shown in this figure, the length of spiral flow formed by the venturi accelerated vortex tool is greater than that produced by the vortex tool alone. This is attributed to the presence of the constriction structure inside the venturi tube, which accelerates the fluid and promotes the formation of the spiral flow. Figure 5: \(Cont.\)  
To further analyze the flow patterns of spiral flow for the venturi accelerated vortex tool, the spiral flow pattern with different gas flow rates was analyzed. The photographed flow fluid is shown in Figure 7 when the inlet liquid flow rate is 3 L/min and the gas flow rate varies from 100 m\({}^{3}\)/h to 600 m\({}^{3}\)/h. As the gas flow rate increases, the length of the spiral flow is also gradually increased, the pitch of the spiral flow is gradually reduced, and the spiral flow becomes more stable. When the gas flow rate reaches 500 m\({}^{3}\)/h, with the increase in gas flow rate, the length and pitch of spiral flow remain basically unchanged. The stable spiral flow is conducive to the carrying of liquid. According to the literature, due to the guidance of the spiral, the fluid obtains centrifugal acceleration, and the heavier liquid is thrown to the pipe wall, forming a rotary flow.