New phase diagram of miscible viscous fingering instabilities in porous media with dead-end pores

Abstract

Classical miscible viscous fingering (VF) instability occurs when a less viscous fluid displaces a more viscous one in porous media with pores that are all well connected. Here, we investigate numerically how non-negligible dead-end pores, together with a limited mass transfer rate Da between the two pore types, affect fingering dynamics. We identify a new stabilizing mechanism induced by a reduction of effective viscosity contrast at an intermediate Da, which leads to a new phase diagram for VF instabilities in a Péclet number— Pe– Da parameter space and an elimination of fingers and tip-splitting at low and large values of Pe, respectively. A scaling analysis, along with an analysis of interfacial lengths, accurately predicts the boundary of the flow regimes and explains the origin of the new stabilizing mechanism.