Hydraulic fracturing simulation for heterogeneous granite by discrete element method

In this study, a heterogeneous discrete element model of granite was built considering different mineral contacts, different mineral grains, and the percentages of minerals which were obtained from analysis of the gray-scale values of the rock picture. First, the contacts and grains parameters were fixed by simulating triaxial compression and fracture toughness tests. Then, the permeability of the numerical model was calibrated on constant head tests. Finally, a coupled hydro-mechanical code was used to investigate the hydraulic fracturing under different conditions, considering the influences of permeability, fluid viscosity, fluid injection rate, boundary stress, pre-existing cracks, heterogeneity and weak layer.