Pseudo-slug flow is widely encountered in gas wells or pipelines with liquid-loading issues. Pseudo-slug characteristics data, such as length, body holdup, frequency, and structure velocity, are very limited in literature despite their importance in modelling and facilities design. Moreover, there are no prior measurements for these variables at large diameter and high pressure conditions. In this study, experiments were performed in a 2° upward 0.1557 m ID flow loop for a pressure range of 1.48 to 2.86 MPa, using mineral oil and nitrogen as testing fluids. Pseudo-slug is characterized based on time-trace signals from Wire-Mesh-Sensors (WMS). The measured length, body holdup, film holdup, frequency, and structure velocity are reported. New pseudo-slug closure relationships are proposed, resulting in noticeable improvements in available model's performance.


Pseudo-slug flow is commonly present in wet gas or gas-condensate production wells or pipelines with liquid-loading issues [1–3]. Pseudo-slug is physically similar to churn flow observed in near vertical pipes [4, 5]. In horizontal flow, this flow pattern may also exist at high gas flow rates [6, 7]. Additionally, it has been reported that as system pressure increases, slugs may gradually evolve into smaller slugs or pseudo-slugs [8, 9], and the transition from slugs to pseudo-slugs may occur at lower vSG [10, 11], suggesting the importance of pseudo-slugs in high pressures.

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