Fingering pattern induced by spinodal decomposition in hydrodynamically stable displacement in a partially miscible system

Abstract

The dynamics of the displacement of one fluid by another in porous media or Hele–Shaw cells depends on the viscosity contrast due to the Saffman–Taylor instability. If the less viscous fluid is displaced by the more viscous fluid, the interface is hydrodynamically stable and, thus, fingering does not occur. Herein, we show experimentally the occurrence of fingering for hydrodynamically stable displacement in a partially miscible system using an aqueous two-phase system. Quantitative correlation between the interfacial deformation and a proposed dimensionless number demonstrates that body force driven by spinodal decomposition induces the fingering instability. Moreover, the fingering observed in this study is completely different from previously reported fingering phenomena in hydrodynamically stable displacement in immiscible and fully miscible systems.