In-Situ Emulsification for Enhanced Oil Recovery: A Microfluidic Study

Abstract

Summary Some enhanced oil recovery processes are designed based on the ability of surface-active agents to emulsify oil the under reservoir flowing conditions. In oilfield operations, the in-situ emulsification process is unknown as some chemicals tend to emulsify oil in one field while they are ineffective in others. Hence, the role of in-situ emulsification to oil recovery seems to be different in various porous rock structures. In the present study, we mimic the flowing conditions on emulsion formations in the co-current flow of two immiscible fluids through a confined space and investigate the effect of in-situ emulsification on the oil recovery from fractured and unfractured media. A flow focusing microfluidic device is used to study the droplet formation in the co-current flow of oil and water through a capillary constrict. The configuration represents the snap-off process when two immiscible fluids pass through a throat to a pore body. The generated droplets are accumulated and directed into a second microfluidic chip saturated with oil. Two types of microfluidic chips are used to evaluate the oil displacement process: one representing the pore-network of a homogeneous rock and the other contains microfractures resembling a matrix-fracture system. The dripping flow regime in the flow focusing device corresponded to the emulsion formation in the reservoir. It can be manipulated based on the dimensionless numbers of the Capillary number (for the continuous phase) and the flow rate ratio. We report the contribution of in-situ emulsification to oil recoveries is not much in the relative homogeneous porous medium. But emulsions can block the fractures directing the water into the matrix, which can significantly enlarge swept areas in the fractured medium Compare to the emulsions with low interfacial tension, the emulsions with high interfacial tension may be more favorable to enhance oil recovery in the fractured-matrix medium.