Upward gas-liquid flow in concentric and eccentric annular spaces
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abstract
A limited amount of research exists on upward gas-liquid flow in annular spaces. This is a common scenario in drilling operations, especially in underbalanced drilling, and in high production wells. To carry out this study, a 40 meter high laboratory facility with an annulus flow loop composed of a 5-1/2 inch outer pipe and a 2-3/8 inch inner pipe was used, with tap water as the liquid phase and compressed air as the gas phase. This study's objective was to phenomenologically characterize gas-liquid flow in annular space and to investigate possible causes of unexpected periodic formation of liquid slugs in the annulus. The work also assessed potential effects of eccentricity of the inner pipe, extracted empirical relationships between two-phase flow parameters (e.g. pressure drop, holdup, and Reynolds and Weber numbers) for both concentric and eccentric configurations, and tested ramp-up sequences to mimic possible subsequent accumulation of liquid in the annulus. The findings from this study revealed that the total pressure drops in concentric and eccentric cases are similar at high gas superficial velocities; however, trends suggest that an eccentric inner pipe causes higher pressure drops at low gas superficial velocities. This is probably due to observed local liquid accumulations around the couplings of the inner pipe when in eccentric configuration. The presence of couplings affects the stability of the Taylor bubble in seemingly slug flows. No liquid accumulation was seen in any of the ramp-up scenarios tested. In ramp-up tests, pressure gradient spikes at the beginning of each test were found to be strongly dependent on the ramp slope. This work contributes to the understanding of gas-liquid flow phenomena observed in the field, both in wells and in risers, when localized liquid flow reversal and/or accumulation may lead to gas production impairments. This work also sheds some light on how to best operate wells and facilities, and particularly on how to manage production ramp-ups. 2014, Society of Petroleum Engineers.
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SPE Latin American and Caribbean Petroleum Engineering Conference Proceedings
