Experimental observations of fracture dissolution: The role of Peclet number on evolving aperture variability

[1] Dissolution of the surfaces of rock fractures can cause significant alteration of the fracture void space (aperture) and fracture permeability (k). Both surface reaction rates and transport of reactants within the fracture can limit local dissolution. We investigated the role of Peclet number (Pe), a measure of the relative importance of advective and diffusive transport of reactants, on fracture dissolution in two identical transparent analog fractures with different initial values of Pe (Peo). High-resolution light-transmission techniques provided direct measurements of the evolving aperture field during each experiment. For Peo = 54 distinct dissolution channels formed, while for Peo = 216 we measured minimal channeling and a reduction in short wavelength aperture variability. The nature of the dissolution patterns strongly influenced the relative increase in k. A 110% increase in the mean aperture due to dissolution resulted in estimated permeability increases of 440% and 640% for the Peo = 54 and Peo = 216 experiments, respectively.