Permeability evolution in open fractures during precipitation and dissolution - A phase-field study

Abstract

In dilated fractures in the Earth’s crust fluid flow in combination with precipitation or dissolution processes can occur, which in turn influences the mechanical and transport properties of the rock system. We use a phase-field modeling framework to investigate these processes of epitaxial crystal growth and dissolution on the fracture walls of crystalline rock systems on microscale. Fluid flow simulations are performed and analyzed during intermediate crystallization and dissolution stages and the obtained hydraulic properties of the partly open fractures are compared to existing literature. The systematic simulation studies show how the rock properties are affected by factors as mineral type with different crystal morphologies, fracture type (inter- vs. transgranular), aperture of the open fracture, and presence of accessory minerals. The results indicate that within the considered parameter space the flow paths remain open until late stages of fracture sealing. Moreover, the long-term permeability and porosity evolution is strongly affected by fracture surface heterogeneities and initial fracture apertures. The simulations enable insights into the evolution of microstructural and fluid flow characteristics and can lay the basis for applications in fractured porous media as groundwater protection, geothermal and hydrocarbon reservoir prediction, water recovery, or storing H2 or CO2 in the subsurface.