CHEMICAL DISSOLUTION OF A POROUS-MEDIUM BY A REACTIVE FLUID .2. CONVECTION VS REACTION, BEHAVIOR DIAGRAM

We study the type of dissolution patterns produced by the flow of reactive fluids in porous media when forced convection, molecular diffusion and surface reaction are the only phenomena occurring. We show that the behavior of a given experiment can be situated on a two-dimensional ''phase'' diagram, where a dimensionless kinetic number is plotted vs a Peclet number. This representation clearly displays the transitions that can be expected between the three different reactive-flow regimes. Although the diagram has been established for the simple geometry of a straight capillary, we show that it can be extended to flow through porous media, as confirmed experimentally. At the macroscopic scale, a specific type of dissolution pattern corresponds to each one of the three regimes. The various models describing the growth of these dissolution patterns are briefly reviewed, and their limits of validity are logically deduced from the diagram.