Fully Hydro-Mechanically Coupled Experiments and Simulations on Rough Fractures Subjected to High-Pressure Fluid Injection

This work presents fully hydro-mechanically coupled experiments and simulations in heterogeneous fractures. Cylindrical specimens with an artificial fracture normal to the cylinder axis were axially loaded to evaluate: (i) fracture normal closure; (ii) fracture contact stress evolution; and (iii) fracture normal closure and fluid injection pressure response. The laboratory experiments were simulated with the GEOS framework, which captures the non-linear behavior of fracture normal closure and fluid pressure response. To apply the developed model on the field scale, a heterogeneous fracture aperture field is created from aperture data recorded under zero-stress on natural tensile fractures from the Grimsel Test Site (GTS), Switzerland. The field stresses measured in the GTS are applied on the model domain, yielding the unique aperture distribution and stress perturbations in the rock mass associated with the applied stress state. Next, fluid is injected into the fracture center and tortuous flow channeling is observed. Increasing fluid injection pressures result in localized fracture opening, which leads to an increasingly non-linear relationship between fluid injection flow rate and pressure.