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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.

Capillary effects can be important in immiscible flow in heterogeneous media, particularly at low capillary numbers. Experiments are performed to study steady-state saturation profiles during drainage in 3D porous media with sharp changes in permeability. It is found that the saturation response is closely linked to the permeability variation. The results are in good agreement with numerical simulations based on a macroscopic description.