This paper investigates oil-water two-phase flows in microchannels of 793 and 667 m hydraulic diameters made of quartz and glass, respectively. By injecting one fluid at a constant flow rate and the second at variable flow rate, different flow patterns were identified and mapped and the corresponding two-phase pressure drops were measured. Measurements of the pressure drops were interpreted using the homogeneous and Lockhart-Martinelli models developed for two-phase flows in pipes. The results show similarity to both liquid-liquid flow in pipes and to gas-liquid flow in microchannels. We find a strong dependence of pressure drop on flow rates, microchannel material, and the first fluid injected into the microchannel.Onétudie dans cet article lesécoulements diphasiques huile-eau dans des micro-canaux de 793 m et 667 m de diamètre hydraulique faits de quartz et de verre, respectivement. En injectant un fluideà un débit constant et le secondà un débit variable, différents schémas d'écoulements ontété observés et représentés en diagrammes, et les pertes de charge diphasiques correspondantes ontété mesurées. Les mesures de perte de charge ontété interprétéesà l'aide du modèle homogène et du modèle de Lockhart-Martinelli mis au point pour lesécoulements diphasiques dans les conduites. Les résultats montrent une similaritéà la fois avec l'écoulement liquide-liquide et l'écoulement liquide de gaz dans des microcanaux. On a trouvé une forte dépendance de la perte de charge aux débits, au matériau des micro-canaux et au premier fluide injecté dans le micro-canal.

Two‐phase (air‐water) flow experiments were conducted in horizontal artificial fractures. The fractures were between glass plates that were either smooth or artificially roughened by gluing a layer of glass beads to them. One smooth fracture with an aperture of 1 mm and three rough fractures, one with the two surfaces in contact and two without contact, were studied. For both types of fractures, the flow structures are similar to those observed in two‐phase flow in a pipe, with structures (bubbles, fingering bubbles, films, and drops) depending on the gas and liquid flow rates. The pressure gradients measured for different liquid and gas velocities were interpreted by three models. First, using Darcy's law leads to relative permeability curves similar to conventional ones for porous media. However, these curves depend not only on saturation but also on flow rates. This effect is caused by inertial forces which are not included in this approach. Second, the standard approach for two‐phase flow in pipes (Lockhart and Martinelli's equation) agrees with experimental results, at least for small pressure gradients. Finally, the best fit was obtained by treating the two phases as one homogeneous phase. All the properties are averaged, and the pressure drop is deduced from an empirical correlation between the two‐phase Reynolds number and the friction factor.

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[1] Two-phase flow through fractured media is important in geothermal, nuclear, and petroleum applications. In this research an experimental apparatus was built to capture the unstable nature of the two-phase flow in a smooth-walled fracture and display the flow structures under different flow configurations in real time. The air-water relative permeability was obtained from experiment and showed deviation from the X curve behavior suggested by earlier studies. Through this work the relationship between the phase channel morphology and relative permeability in fractures was determined. A physical tortuous channel approach was proposed to quantify the effects of the flow structure. This approach could replicate the experimental results with a good accuracy. Other relative permeability models (viscous coupling model, X curve model, and Corey curve model) were also compared. Except for the viscous coupling model, these models did not interpret the experimental relative permeabilities as well as the proposed tortuous channel model. Hence we concluded that the two-phase relative permeability in fractures depends not only on liquid type and fracture geometry but also on the structure of the two-phase flow.

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