E-mail: edward.bolton@yale.edu

Dissolution and precipitation via forced flux injection in a porous medium with spatially variable permeability: Kinetic control in two dimensions

by Edward W. Bolton, Antonio C. Lasaga, and Danny M. Rye

accepted by Journal of Geophysical Research - Solid Earth Section, February 1997

We model kinetically controlled dissolution and precipitation of quartz in a porous medium. Our specific focus is on the spatial pattern of flow velocities and of changes in solute concentration and porosity introduced by heterogeneities in the initial permeability field. Upon a background permeability field, we impose isolated "crack-like" zones of high permeability and low surface area to fluid volume ratios. Our two-dimensional modeling of forced flux injection of over-- and under--saturated fluid reveals features inaccessible to previous homogeneous permeability studies. Although realistic velocities give rise to narrow boundary layers in the solute concentration, disequilibrium is favored in the high permeability zones yielding plume--like structures of solute concentration. Aside from the rapid changes in porosity near the injection level, the other regions of rapid porosity change occur just downstream from the cracklike zones, where fluid more out of equilibrium encounters regions of higher surface area. Flow rates are significantly enhanced even between isolated high permeability zones, an effect which is even more dramatic for both closer "crack" spacing and higher permeability contrasts. Undersaturated injection leads toward permeability homogenization along the flow direction, whereas oversaturated injection tends to increase permeability heterogeneities along the flow direction.