Flow behavior in a radial Hele-Shaw cell with wettability heterogeneities

Fingering instabilities develop when a low-viscous fluid displaces a high-viscous fluid in porous media; they are unfavored in various natural and industrial processes. Classical Hele-Shaw studies of viscous fingering have not addressed the role of surface wettability heterogeneity, a common property of many natural and engineered solid surfaces. We describe an experimental investigation of the effect of wettability heterogeneity on flow behavior in radial Hele-Shaw cells. The density, distribution, and orientation of wettability defects are considered in the analysis. Results show that uniformly/randomly distributed wettability defects can roughen finger boundaries, broaden growth regions, and increase displacement efficiency. However, the distribution and orientation of wettability heterogeneities also determine whether viscous fingering is suppressed or enhanced. Lower flow rates enhance capillary and wetting phenomena and magnify wettability effects on the displacement pattern. Displacement efficiencies ranging from 0.936 to 0.508 are observed when viscous fingering is suppressed and enhanced, respectively. Our study provides insights into the interpretation of flow phenomena and potential manipulation of fingering instabilities in heterogeneous porous media.