Fracture mechanics approximation to predict the breakdown pressure using the theory of critical distances

The breakdown pressure is an important parameter that influences the hydraulic fracturing process of the rock. This paper presents a new approach for the prediction of the breakdown pressure in hydraulic fracturing based on the theory of critical distances. The proposed method of analysis assumes that a pressurized crack is formed at a critical distance into the material prior to the unstable propagation. The breakdown pressure is calculated using an analytical approximation of the mode I stress intensity factor for this pressurized crack. A series of hydraulic fracturing experiments were conducted and the test results were compared with those predicted from the proposed method of analysis. The approximation aligns with these test results as well as with published results from independent hydraulic fracturing experiments.