## 4 Data Analysis of Gas-Liquid Separation Efficiency in Two-Phase Flow
### Gas-Water Two-Phase Flow Separation Efficiency with 5% Gas Holdup  
The DGLS's gas holdup is 5%, and the water holdup is 95%. The flowmeter is placed in the central pipe. Therefore, as long as the gas holdup in the central pipe is lower than 10% of the total gas holdup at the wellbore inlet, it is considered to meet the engineering requirements. The gas holdup number in the central tube is brought into Equation (19), and then calculated the gas-liquid separation efficiency, i.e., the DGLS's gas-liquid separation efficiency. As shown in Figure 4, the color chart for the vertical axis shows the phase's volume content; red indicates that it is 100%, blue indicates that it is 0%. Figure 4a-e show a cloud diagram of the gas phase distribution in the casing when the total flow is 20 m\({}^{3}\)/d-60 m\({}^{3}\)/d. Red represents the gas phase and blue represents the water phase. In Figure 4a-d, when the fluid enters the wellbore, most of the gas-water two-phase flow's flow pattern consists of finely dispersed gas in the water bubble flow (VFD G/W bubble flow). In Figure 4e, most of the gas-water two-phase flow's flow pattern consists of dispersed gas in water bubble flow (D G/W bubble flow) and VFD G/W bubble flow. When the fluid continues to rise under the collecting umbrella, the stratification of the gas phase and the liquid phase occurs due to the varying density. After the gas phase accumulates to form a gas cap, we opened the exhaust valve and allowed it to enter the exhaust channel, so as to isolate the gas phase and the liquid phase. Then, we discharged the gas phase through the exhaust channel, and the gas-liquid two-phase flow's flow pattern consisted primarily of bubble flow in water. With the increase in total flow rate, the bubble size at the inlet of the wellbore increased. Additionally, the bubbles discharged through the exhaust channel and gradually expanded but remained part of the G/W bubble flow. At the same time, observation of the central pipe showed that its gas content had also increased along with the increase in total flow.  
The simulation analysis results are shown in Table 2 through the numerical simulation of the total flow of 20 m\({}^{3}\)/d-60 m\({}^{3}\)/d. DGLS can achieve good gas-liquid separation efficiency within the range of 20 m\({}^{3}\)/d-30 m\({}^{3}\)/d, and its error is within the allowable range (according to the conditions (e)). With the increase in flow rate, the gas holdup in the central tube also increases. Although the range of gas holdup in the central tube is small, the DGLS's gas-liquid separation efficiency drops. The larger the total flow rate, the more complex the flow state, and the less pronounced the gas-liquid separation effect. When the flow is 20 m\({}^{3}\)/d, it can achieve a very high gas-liquid separation efficiency. However, it cannot meet the demand after more than 20 m\({}^{3}\)/d, and the gas separation effect cannot be achieved at this level.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Gas Holdup**} & **Total Flow** & **Gas Flow** & **Water Flow** & **Reynolds** & **Turbulence** \\  & **(m\({}^{3}\)/d)** & **(m\({}^{3}\)/d)** & **(m\({}^{3}\)/d)** & **Number** & **Intensity (\%)** \\ \hline  & 20 & 2 & 18 & 2389 & 6.05 \\  & 30 & 3 & 27 & 3584 & 5.75 \\
10\% & 40 & 4 & 36 & 4779 & 5.54 \\  & 50 & 5 & 45 & 5974 & 5.39 \\  & 60 & 6 & 54 & 7168 & 5.27 \\ \hline \end{tabular}
\end{table}
Table 1: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Total Flow (m\({}^{3}\)/d)**} & **20** & **30** & **40** & **50** & **60** \\ \hline \(\eta_{g}\)(\%) & 90.5 & 84.4 & 79.5 & 75.1 & 66.1 \\ \hline \end{tabular}
\end{table}
Table 2: Gas-water separation efficiency at gas holdup 5%.