# Study on Explosive Fracturing Mechanism of Qianjiang Shale Oil
## 3 Results and Discussion
### Simulation of Different OB Explosives Explosion  
During the process of explosive fracturing, the formation stress induced by fractures significantly increases. This is attributed to the substantial energy released by the explosion, which subjects the formation rocks to intense impact and compression, leading to the redistribution and escalation of formation stress. Additionally, pore pressure undergoes considerable alteration. The explosive fracturing disrupts the original structure of the formation rock, creating new fractures and pores that serve as migration pathways for fluids (such as oil, gas, and water), thereby modifying the original pore pressure distribution. Moreover, an excessive amount of explosives can lead to the generation of new fractures, potentially causing microseismic events. This occurs because crack expansion and formation deformation during explosive fracturing induce friction and shear sliding between rock layers, which may result in minor seismic activity when this sliding reaches a critical level. Although these microseismic events are of small magnitude, they can influence formation stability and well integrity. When selecting explosives, a comprehensive evaluation must be conducted based on the specific blasting objectives, geological conditions, and safety requirements. To accurately assess the dynamic response of reservoir rocks under explosive loading, simulations of blasting damage using different types of OB explosives are performed under identical charging radii while maintaining consistent boundary conditions and constraints. The explosion effects, energy release, and damage distribution to the reservoir rocks are then analyzed. The distribution of rock damage caused by different OB explosives at charge radii of 8 cm, 7 cm, and 6 cm is illustrated in Figure 10. As shown in the figure, both the type of explosive and the charge radius have a direct impact on the reservoir damage zone, resulting in variations in the size and shape of the formed crushing and fracture zones. As the charge radius decreases, the number of cracks and the extent of crack propagation gradually diminish. Under varying charge radii, the damage area of NTNMT can extend throughout the entire reservoir rock, forming multiple main fractures interspersed with branch fractures and micro-fractures. The fracture coverage exceeds 18.2%. Notably, when the charge radius is 7 cm, the fracture coverage reaches its peak at 18.8%. In contrast, the damage areas caused by DEGDN and TNT exhibit greater activity in the horizontal direction compared to the vertical direction. Except for a charge radius of 6 cm, where only crushing zones are observed within the reservoir, the crack percentage for DEGDN and TNT exceeds 10% under other charge radii. The volume of the void formed post-explosion varies depending on both the explosive type and charge radius. For a given explosive type, the cavity volume decreases as the charge radius decreases. When the charge radius is constant, NTNMT produces the largest cavity volume, while DEGDN yields the smallest, with a maximum difference of 0.62%. Following explosive initiation, the energy released by the explosion propagates through the reservoir rocks in the form of kinetic and internal energy [45], as illustrated in Figure 11. The kinetic and internal energies generated vary with different charging radii and types of OB explosives. During the stress wave impact phase, the kinetic energy rapidly increases to a peak pressure before quickly decreasing and transitioning to a secondary peak value. Compared to the first peak, the second peak attenuates by approximately 23-37%, eventually stabilizing. As the charge radius increases, a higher kinetic energy peak will be generated. The initial internal energy is derived from the explosive itself, which is rapidly released upon detonation and subsequently reduced to its minimum value.