Supporting Information for "Solute mixing regulates heterogeneity of mineral precipitation in porous media"

Cil, M. B., M., Xie, A. I., Packman, and G., Buscarnera (2017), Solute Mixing Regulates Heterogeneity of Mineral Precipitation in Porous Media, Geophys. Res. Lett., 44, doi:10.1002/2017GL073999.

Abstract

Synchrotron X-ray microtomography was used to track the spatiotemporal evolution of mineral precipitation and the consequent alteration of the pore structure. Column experiments were conducted by injecting CaCl₂ and NaHCO₃ solutions into granular porous media either as a premixed supersaturated solution (external mixing) or as separate solutions that mixed within the specimen (internal mixing). The two mixing modes produced distinct mineral growth patterns. While internal mixing promoted transverse heterogeneity with precipitation at the mixing zone, external mixing favored relatively homogeneous precipitation along the flow direction. The impact of precipitation on porewater flow and permeability was assessed via 3D flow simulations, which indicated anisotropic permeability evolution for both mixing modes. Under both mixing modes, precipitation decreased the median pore size and increased the skewness of the pore size distribution. Such similar pore-scale evolution patterns suggest that the clogging of individual pores depends primarily on local supersaturation state and pore geometry