In Situ Microemulsion Formation In Enhanced Oil Recovery

Abstract

The formation of microemulsions of an EOR surfactant with n-decane was studied in a microfluidic setup using fluorescence microscopy. Generally microemulsions are studied under static conditions by means of phase behavior tests. However, oil mobilization fromreservoirs is a dynamic process and therefore it is important to understand how microemulsions formunder dynamic conditions. The microemulsion was formed in situ in T-junctions and dead end channels whichwere etched in glass microchips. Using a solvatochromic fluorescent dye (Nile Red) real time visualization of the aqueous phase, oil phase and microemulsion was possible. The T-junction geometrywas used to study initial mixing and consequential formation of microemulsion while both the aqueous phase and the oil phase were mobile. The dead end channel geometry allowed us to study the emulsification when only the aqueous phase was injected into an initially oil saturated microchip. The surfactant concentration and injection rates were found to have an effect on the emulsification rate and the flow dynamics in the T-junctions. In the dead end channels, the emulsification was mainly driven by diffusion and the gradients in the concenration of the chemicals. Some of the results of the dynamic experiments deviated from what would be expected fromthe phase behavior tests. Results of the experiments were reproduced where possible using commercial software (ComsolMultiphysics) which helped to get a qualitative understanding of the flow dynamics. An analyticalmodel was implemented using the saturation profiles observed in the experiments. Possible emulsification mechanisms were identified.