CHEMICAL DISSOLUTION OF A POROUS-MEDIUM BY A REACTIVE FLUID .1. MODEL FOR THE WORMHOLING PHENOMENON

A quantitative model describing the flow properties of dissolution patterns, called ''wormholes'', is described. These patterns are created when a reactive fluid is injected into a soluble porous medium and when dissolution kinetics is mass transport-limited. The flow properties of the whole wormhole pattern can be described by a single parameter, its ''equivalent size'', deduced simply from Darcy's law. The dependence of equivalent size on all physical parameters is studied experimentally in various porous medium-reactive fluid systems. We use physical arguments to interpret experimental results which allow derivation of a simple dimensionless equation relating equivalent size to physical parameters. This equation describes both linear geometries for which patterns are nonfractal, and the cylindrical case yielding patterns of fractal geometry, with good accuracy and without any adjustable parameters.