Optical characterization of reservoir interfaces and study of microemulsion phase transition behavior using the OIRD technique

The intermolecular interactions between microemulsions and rock interfaces are key to regulating the properties of reservoir interfaces. Therefore, the focus of research on reservoir interface properties lies in the coupling mechanism between hydrogen bonding networks and interfacial electric potentials, which macroscopically manifests as the relationship between interfacial layer thickness and dielectric properties. In this study, the oblique-incidence reflectivity difference (OIRD) technique—highly sensitive to variations in interfacial thickness and permittivity—is employed for the optical characterization of reservoir rocks and the study of microemulsion phase transition behavior. The two-dimensional OIRD imaging experiment achieves the physical characterization of mineral and organic component distribution on oil shale surfaces. Diffusion kinetics experiments reveal that individual microemulsion components exhibit significantly different diffusion behaviors on the oil shale surface. These differences are influenced by factors such as fluid polarity, interfacial tension, mineral composition, and pore structure. Phase transition experiments demonstrate that microemulsions undergo phase transitions from water-in-oil (W/O) to bicontinuous and eventually to oil-in-water (O/W) with increasing water content. This work contributes to the study of reservoir interfacial properties and microemulsion enhanced oil recovery.