A simplified approach to hydraulic fracturing of rocks based on Finite Fracture Mechanics

This work presents a coupled approach, based on Finite Fracture Mechanics (FFM), to preliminarily investigate hydraulic fracturing of rocks. The novelty of the criterion relies on the assumption of a finite crack extension and on the simultaneous fulfillment of a stress requirement and the energy balance. Two material constants are involved, namely, the tensile strength and the fracture toughness. The FFM unknowns are represented by the critical crack advance, which results a structural parameter and not a simple material one, and the breakdown pressure. The study investigates the longitudinal failure behavior of both impermeable and permeable rocks by supposing that growing cracks are loaded by a pressure proportional to that acting on the borehole wall. The stability growth of hydraulic fractures is discussed case by case. The approach is validated against experimental data available in the literature by considering the effect of rock permeability, fluid viscosity and flow rate.

Automated summary

This study presents a new approach, based on Finite Fracture Mechanics (FFM), to preliminarily investigate hydraulic fracturing of rocks. The approach considers a finite crack extension and the fulfillment of both a stress requirement and an energy balance. The unknowns in FFM are represented by the critical crack advance, a structural parameter, and the breakdown pressure. The study investigates the failure behavior of impermeable and permeable rocks under longitudinal loading conditions. The approach is validated against experimental data by considering the effect of rock permeability, fluid viscosity, and flow rate.