The local two-phase gas/liquid flow behavior at a high velocity gradient is essential for managing gassy wells. In this study, the methane/water bubbly flows passing through a perforated pipe were characterized in a 10.4-m flow loop in which the pressure was varied up to 5.5 MPa at 291 K. To characterize the two-phase flow behavior at the bore, we obtained the bubble sizes from high-speed photographs and digital image analysis. As the flow velocity and/or pressure increased, the flow patterns shifted from bubbling to jetting, suggesting that the local two-phase flow pattern can control the bubble size in flowlines.


Multiphase flow control in wells and pipelines is crucial in the oil and gas industries. The most important components affecting the production efficiency, cost, and safety of gassy wells are the gas/liquid separators and multiphase flow pumps. For instance, the gas/liquid separators reduce the void fraction at the pump intake, thereby minimizing the pump surging (Hua et al., 2012; Gamboa and Prado, 2011). Phase separation reduces the risk of pipe plugging through the formation of gas hydrates (Shimizu et al., 2017; Joshi et al., 2013; Sakurai et al., 2014). In gas production from offshore natural gas hydrate reservoirs, these devices must handle two-phase flows under variable pressure and void fraction in a natural-gas/seawater mixture, while stably maintaining the bottom-hole pressure below the three-phase equilibrium pressure (Cyranoski, 2013). Optimizing the performance of these devices in such situations is a necessary yet challenging task.

Bubbles formed by breakup and coalescence are of paramount importance in industrial heat and mass transport processes and are typically generated by a gas distributor (Idogawa et al., 1987; Quinn and Finch, 2012; Tsuge and Hibino, 1983) or a rotating impeller (Kracht and Finch, 2009; Minemura et al., 1998; Masui et al., 2011). Hence, bubble formation has been studied extensively for decades. However, few studies have focused on the bubble behavior under a high velocity gradient in pipelines, where bubbles assist the transmission of the gas/liquid flow mixture in practical production fields.

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