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

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 Peclet 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. Published under an exclusive license by AIP Publishing