Permeability enhancement through reactive transport

Reactive transport processes are fundamental in various geological settings, driving ore deposit formation, rock alteration, and deep geothermal energy systems. These processes fundamentally depend on interactions between fluids and the surrounding rock, resulting in dynamic changes in permeability structures and mineral composition over time. In low-porosity systems, creating interconnected porosity is essential for efficient fluid transport. This is particularly critical for deep geothermal energy systems, where mechanically induced permeability enhancements are often viewed as societally sensitive.

To investigate the coupling of fluid-driven mineral replacement reactions and porosity formation, we conducted hydrothermal batch experiments across different reaction durations, analyzing fluid-rock interactions in granitoid systems with varying lithologies and concentrations of F-bearing aqueous fluids under acidic conditions. Using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), and fluid chemical analyses, we characterized and quantified mineralogical and chemical changes while assessing the microstructural evolution of rock samples exposed to reactive fluids.

Our results show that fluid-rock interactions significantly enhance porosity, driven by mineral dissolution and the formation of denser phases that pseudomorphically replace the original mineral assemblages. In some cases, pores were partially filled with newly precipitated amorphous silica and F-bearing minerals, preferentially replacing feldspar and mica within the granitoid. Key findings underscore the potential of reactive transport processes to enhance permeability in granitoid rocks, emphasizing the critical influence of initial fluid composition on both permeability formation and the overall chemical evolution of the rock system.