Liquids in porous media

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Abstract
The basic mechanisms which take place during the displacement of immiscible fluids in porous media have been observed in micromodels and have been modelled. At the pore level, in drainage, the invading fluid chooses the largest throat. In imbibition, the displacement depends on the local geometry. For a large pore-to-throat ratio (aspect ratio), the main mechanism is the collapse of the invading fluid in the smallest channel, without entering the pore. For a small aspect ratio, the wetting fluid invades the pore first, and then the adjacent channels. From observations at the pore level, the author has modelled the displacement on a large scale in some extreme cases by using statistical theories. The different behaviours are then displayed as domains in three phase diagrams: one for drainage and two for imbibition (large and small aspect ratios). At a high rate, when viscous forces are dominant, all the diagrams show a stable domain (described by anti-DLA) and a viscous fingering domain (DLA). In drainage, low capillary numbers lead to capillary fingering represented by invasion percolation. In imbibition, the capillary domain is described either by a compact cluster growth (small aspect ratio) or percolation theory (large aspect ratio). In addition the possibility of flow by film along the roughness of the walls leads to disconnected structures.