Numerical modeling of the interaction between existing and hydraulically-created fractures using the Displacement Discontinuity Method

The displacement discontinuity method (DDM) code, FROCK, is used to model the interaction between existing and hydraulically-created fractures in granite specimens subjected to hydraulic pressure inside pre-fabricated flaws. A stress-based fracture initiation and propagation criterion implemented in FROCK was used to evaluate the fracture initiation stresses and the fracturing patterns. Subsequently, the numerical model was validated by comparing its results with experimental observations under similar loading conditions. It was concluded that the DDM code FROCK successfully simulated the hydraulic fracturing conditions and the macroscopic fracturing patterns observed experimentally. In addition, the fracture initiation pressures predicted numerically are approximately the same as the white patching (i.e. micro-cracking) initiation pressures observed experimentally, which indicates that the input strength parameters used in the crack initiation criterion represent the microscopic strength of the rock.