Research on Damage Characteristics and Fracturing Mechanism of Deep Bedded Shale Penetrated by Shaped Charge Jet

Shale gas, as an important unconventional clean energy resource, plays a significant role in ensuring energy security and promoting low-carbon energy transition. Perforation is a key preliminary process for shale reservoir stimulation, and the quality of the perforation channel and the associated damage characteristics directly affect subsequent fracturing performance. To clarify the influence of bedding angle on shaped-charge jet penetration and fracture response in deep shale, a three-dimensional coupled numerical model consisting of a perforating charge, air domain, and shale target was established using ANSYS/LS-DYNA. A DP46HMX42-Y perforating charge was adopted, and numerical cases with non-bedded shale and bedded shale at angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° were considered. The ALE fluid-structure coupling algorithm was used to simulate the dynamic penetration process of the shaped-charge jet into shale. The jet velocity and morphology evolution, perforation-channel formation, damage distribution, and crack-inducing behavior were systematically analyzed. The results show that the bedding angle has a significant effect on jet penetration. At the same moment, the jet-head velocity generally increases with increasing bedding angle, and the 90° bedded shale exhibits the greatest penetration depth, approximately 10% higher than that of the non-bedded shale. The channel-volume results indicate that bedding structures promote the formation of larger perforation channels, with the most pronounced improvement observed in the 0° and 90° bedding cases. The damage-evolution results show that the total damage volume of bedded shale is generally smaller than that of non-bedded shale, and decreases with increasing bedding angle. Bedding planes exert a clear guiding effect on damage propagation, causing the damage zone to extend along the bedding direction and inducing secondary cracks near bedding interfaces. Further cross-sectional damage analysis indicates that the radius of the compression-shear damage zone is negatively correlated with penetration depth, while the maximum crack length decreases in a fluctuating manner as penetration depth increases. The cross-sectional damage area and fractal dimension also generally decrease with increasing penetration depth. These findings provide numerical guidance for optimizing perforation parameters and improving subsequent fracturing stimulation in deep shale reservoirs.