Molecular-level forces experienced by a surfactant during emulsification can have a significant impact on emulsion structure and effective properties. Understanding the interplay of molecular-level forces and effective phase properties during in situ emulsification is a fundamental question relevant to various subsurface engineering applications. Herein, we use dynamic synchrotron-based X-ray microtomography to capture flow dynamics during an oil emulsification process, whereby brine salinity influences the predominate molecular-level forces. We measure oil recovery, phase viscosities, phase morphologies, contact angles and water relative permeability to elucidate the underlying oil recovery mechanisms. Optimum salinity formed a stable emulsion phase with ultra-low interfacial tension, viscosity high enough to reduce the mobility of the injected solution and a reduced adhesive force that resulted in less contact between oil and solid grains. These mechanisms are attributed to favorable flow dynamics that lead to improved oil recovery that can be tuned by brine salinity.

Yara A. Alzahid, Hussain Aborshaid, Mohanad Asali, James McClure, Cheng Chen, Peyman Mostaghimi, Ying Da Wang, Chenhao Sun, Ryan T. Armstrong, Real-time synchrotron-based X-ray computed microtomography during in situ emulsification, Journal of Petroleum Science and Engineering, Volume 195, 2020, 107885, abstract

Lenormand phase diagram that characterizes our experimental system based on Capillary number (Ca) and viscosity number (υ), which will be explained in the next section. The grey boundaries are system-dependant and only illustrative. The points refer to surfactant at optimum salinity (green), surfactant at under-optimum salinity (yellow) and water flood (blue). The oil/brine diagrams highlight the different emulsion systems created at optimum and under-optimum conditions. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)