## 5 Data Analysis of Gas-Liquid Separation Efficiency in Multiphase Flow
### Analysis of Numerical Simulation Results of Oil-Gas-Water Multiphase Flow  
By numerically simulating the oil-gas-water multiphase flow within the range of 20 m\({}^{3}\)/d-60 m\({}^{3}\)/d, the gas holdup is 5%, the oil holdup is 10%, and water holdup is 85%. We obtained the gas holdup, oil holdup, and water holdup in the central pipe via the volume method. Figure 6 is a cloud diagram of gas-phase distribution under different  
\begin{table}
\begin{tabular}{c c c c c c} \hline
**Total Flow** & **Gas Flow** & **Oil Flow** & **Water Flow** & **Reynolds** & **Turbulence** \\
**(m\({}^{3}\)/d)** & **(m\({}^{3}\)/d)** & **(m\({}^{3}\)/d)** & **(m\({}^{3}\)/d)** & **Number** & **Intensity (\%)** \\ \hline
20 & 1 & 2 & 17 & 2255 & 6.095 \\
30 & 1.5 & 3 & 25.5 & 3383 & 5.794 \\
40 & 2 & 4 & 34 & 4511 & 5.589 \\
50 & 2.5 & 5 & 42.5 & 5638 & 5.435 \\
60 & 3 & 6 & 51 & 6766 & 5.313 \\ \hline \end{tabular}
\end{table}
Table 4: Related parameters of oil-gas-water multiphase flow.  
flow rates; red represents the gas phase, and blue represents the water phase. As the flow increases, the gas holdup in the casing increases, and the gas volume under the collection umbrella gradually decreases, while the gas holdup in the central tube gradually increases. The bubbles in Figure 6 are bigger than those in Figure 4 due to the addition of an oil phase in Figure 6. Most of the gas phase flow pattern in the oil gas water three-phase flow consists of fine bubble flow. Therefore, adding the oil phase not only increases the flow pattern's complexity but also affects each phase's separation velocity. The observation method shows that the gas separation effect is stronger at lower flow rates.  
Figure 7 is a cloud diagram of oil phase distribution under different flow rates. Red represents the oil phase and blue represents the water phase. Due to the low oil content, it is in an oil-in-water state in the figure. As the flow rate increases, the oil volume in the central pipe also increases. Visual observation indicated that the DGLS does not separate the oil from the fluid medium, and oil droplets do not accumulate under the collection umbrella. Rather, the distribution of oil in the central tube is similar to that in the wellbore.  
The numerical simulation results are shown in Table 5. When the total flow is between 20 m\({}^{3}\)/d and 50 m\({}^{3}\)/d, the gas-liquid separation efficiency can surpass 90%, and the results is meeting the conditional (e) and engineering requirements. With the increase in total flow rate, the gas-liquid separation efficiency decreases gradually, that is, when the total flow rate reaches 60 m\({}^{3}\)/d, the gas-liquid separation efficiency is the lowest. From the oil collection efficiency in the central pipe, the DGLS can not only isolate the gas and liquid but also ensure the central pipe's oil holdup. The results show that with the increase in total flow at any time, the oil holdup in the central pipe gradually increases and tends to hold up oil at the inlet. This indicates that the greater the flow, the better the DGLS performs. However, at low flow rates, the oil holdup is the lowest, because the interface between the gas and the oil is not pronounced when oil and gas gather under the umbrella. When the gas-liquid separation valve is opened, the oil phase will also enter the gas channel and discharge. From this point, it cannot enter the central pipe, and so the oil holdup in the central pipe declines. According to the above data analysis, the applicable range of DGLS for oil-gas-water multiphase flow is 20 m\({}^{3}\)/d-50 m\({}^{3}\)/d.  
Figure 6: Cloud diagram of gas phase distribution of gas–oil–water with total flow at (a) 20 m\({}^{3}\)/d; (b) 30 m\({}^{3}\)/d; (c) 40 m\({}^{3}\)/d; (d) 50 m\({}^{3}\)/d; (e) 60 m\({}^{3}\)/d.