Hydraulic Fracture Propagation Across Pre-existing Discontinuities in an Anisotropic Rock: Experimental Evidence and Insights from Scaling Relations

Laboratory experiments have been conducted on anisotropic slate specimens to study the behavior of hydraulic fractures (HFs) when encountering discontinuities. The experiments target specific propagation regimes, including toughness-dominated, lag-viscosity-dominated, and transitional regimes, to examine the influence of rock discontinuities on HF growth paths. Our experimental observations reveal that planar HF propagation is favored in the transitional and lag-viscosity-dominated regimes, where HFs exhibit a greater tendency to cross rock discontinuities. In contrast, a significant influence of discontinuity planes is observed in the toughness-dominated experiments, leading to HF diversion or arrest of the HF. The complexity of fracture paths is found to be closely tied to a dimensionless toughness parameter derived from scaling relations. This study highlights the pivotal role of hydromechanical characteristics in shaping complex HF patterns in anisotropic rocks with pre-existing discontinuities.