Phase diagram of stable miscible displacements in layered porous media

We study miscible fluid displacement in heterogeneous porous media, in the presence of gravity, where the heterogeneity consists of multiple layers. Miscible fluids of different density and viscosity contrasts are used, such that the displacement is hydrodynamically stable. Depending on the values of the control parameters, the overall fluid displacement exhibits either an enhancement of the effect of heterogeneity or a damping. For a sufficiently large viscosity and/or density contrast, the effect of heterogeneity is overcome and the multi-layer system behaves as a single homogeneous layer. We determine experimentally an associated phase diagram and compare our data to a theoretical model valid for systems of large aspect ratio.