Heavy Oil Emulsification and Emulsions Flow through Porous Media: A Microfluidic Experimental Study

Summary Chemical cold production of heavy oil represents a highly promising development technology. It reduces oil viscosity by emulsifying heavy oil into oil-in-water (O/W) emulsions via surfactants, thereby enhancing fluid mobility. Due to hydrodynamic effects and the inherent instability of emulsions, the formation and transport of emulsions in porous media involve complex dynamic processes. In this study, a series of microfluidic chips were designed to investigate diverse mechanisms of heavy oil emulsification, including snap-off, pinch-off, breakup of drops flowing past an obstacle, and detachment of pore-wall adherent oil. Specifically, the effects of hydrodynamic conditions and oil viscosity on emulsification and transport were systematically investigated. Meanwhile, the transport mechanisms and droplet-size evolution of emulsions within porous media were explored. The results indicate that snap-off and breakup of drops flowing past an obstacle occur at lower capillary number (Ca) thresholds, which further decrease with increasing oil viscosity. In contrast, pinch-off and detachment of pore wall-adherent oil require higher Ca thresholds, which increase with oil viscosity. The flow mechanisms of emulsions in porous media involve intricate interactions, such as droplet deformation, rupture, coalescence, preferential flow, and interdroplet collisions. The droplet size decreases with higher capillary numbers but increases with increased oil viscosity. Additionally, the discontinuous emulsion flow effectively regulates flow profiles. This study elucidates the emulsification and transport dynamics of emulsions in porous media, providing theoretical support for green heavy oil development and novel insights into emulsification and flow phenomena across related disciplines.