​Direct observations of oil-water-rock contacts at resolutions high enough to resolve the details of wetting contacts are key for improving our understanding of multiphase flow phenomena in mixed-wet reservoir rocks. I present results of a study where we imaged pore-scale fluid-fluid-solid contacts with nanometer resolution using cryogenic broad ion-beam polishing in combination with scanning electron microscopy and phase identification by energy-dispersive X-ray analysis. In sandstones, the non-wetting oil phase separated from quartz surfaces by a thin brine film, but also had direct contacts between oil and rock at asperities and clay aggregates, which act as pinning points and cause discontinuous motion of the oil-water-solid contact line.

We used the same technique of (Cryo-BIB-SEM) to study mineral/oil/brine contacts in reservoir carbonates. We compare two types of carbonate reservoirs: a fine-grained and a coarse-grained limestone. We first quantify the porosity with BIB-SEM and high resolution virtual optical microscropy (ViP) and derive the spatially resolved pore connectivity of the rock from BIB-SEM on Wood's Metal (WM) injected subsamples. Following this, subsamples were saturated with an oil analog, and then flooded with brine and brine and imaged by Cryo-BIB-SEM and EDS followed by automated image analysis. Our results interface length, contact angles, effect of asperities on the scale of a few tens of nanometers

This study showed that the technique permits the testing of predictions on the morphology and dynamics of fluid-fluid-mineral contact at nanoscale which is not possible with other imaging methods, such as X-ray microCT.