Influence of pre-existing discontinuities and bedding planes on hydraulic fracturing initiation

Pressure-driven fracturing, also known as hydraulic fracturing, is a process widely used for developing geothermal resources, extracting hydrocarbons from unconventional reservoirs such as tight sandstone and shale formations, as well as for preconditioning the rock-mass during deep mining operations. While the overall process of pressure-driven fracturing is well understood, a quantitative description of the process is difficult due to both geologic and mechanistic uncertainties. Among them, the simulation of fractures growing in a complex heterogeneous medium is associated with computational difficulties. Experimental evidence based on micro-seismic monitoring clearly demonstrates the important influence of rock mass fabric on hydraulic fracture development, and the interaction between fluid-driven fractures and pre-existing discontinuities. However, these components are not well accounted for by standard numerical approaches. Thus, the design of hydraulic fracturing operations continues to be based on simplified models whereby the rock mass is treated as a homogeneous continuum. The purpose of this paper is to present the preliminary results obtained using the combined finite-discrete element technology to study the interaction between fluid driven fractures and natural rock mass discontinuities.