Abstract
Low permeability is a key geological factor constraining the development of shale gas, and reservoir modification to improve its permeability is a prerequisite. Controlled shock wave fracturing can induce the formation of complex fractures in reservoirs and is expected to become an important means of reservoir modification. However, the mechanism of controlled shock wave fracturing in shale and the geological engineering control factors are unclear. Therefore, this article reveals the mechanism and effect of shock wave modification through small-scale experiments and large-scale numerical simulations. Results show that as the impact number increases, a significant increase in large fractures and fracture connectivity within the shale samples is observed, while the correlation between the geometric parameters of the fractures and the number of impacts is weak. High-energy input in the model will cause a larger range of damage to the rock, accompanied by a smaller attenuation index, indicating that the speed of energy attenuation plays a decisive role in rock damage. The influence of crustal stress is greater than the speed of energy attenuation, and higher crustal stress will inhibit the formation of fractures. A moderate increase in the number of controllable shock waves is beneficial for the fracturing effect; however, further increasing the loading number of controllable shock waves will weaken the strengthening effect of the fracturing effect.