Numerical Study on the Rock-Breaking Mechanism and Stress Superposition Effect of Double-Hole Delayed Blasting in Deep Reservoirs

Abstract

With the application of electronic detonators, delayed blasting is considered a very effective method to improve rock fragmentation, and this technique is widely used in practical engineering. Therefore, it is necessary to study the rock-breaking mechanism of double-hole delayed blasting. In this paper, based on the finite difference method, the influence of double-hole delayed blasting on the reservoir permeability was quantitatively analyzed by adopting the adjacent hole spacing, delay time, and decoupling coefficient (K) as variables and the permeability increment as an evaluation index. Based on the parameters studied in this paper, it was found that the effect of the delay time on the reservoir permeability depends on the hole spacing. When the hole spacing is less than 20ra (ra is the borehole radius), a reasonable delay time could significantly increase the reservoir permeability, but when the hole spacing is greater than 20ra, the delay time does not affect reservoir permeability enhancement. The decoupling coefficient could control the attenuation speed of shock wave energy. For K = 2, energy attenuation occurred the slowest, and the reservoir permeability increase effect was the best. Based on site-scale numerical simulations, the mechanism of stress superposition between boreholes was revealed, and the position of stress superposition was controlled by adjusting the delay time to break hard reservoir rock so that the cracks between two holes were connected, i.e., accurate reservoir reconstruction was achieved. This work provides a certain guiding basis for actual engineering applications.