Injecting high-pressure fluid into a reservoir rock mass will change the mechanical properties of the rock; the strength and safety of a shale well wall are also extremely critical. In order to investigate the law of variation in water-sensitive shale strength during fracturing, an experimental study on the mechanical properties of shale under high confining pressure and water–rock coupling was carried out. Taking water-sensitive shale rock as the research object, the effects of high confining pressure and water content on the mechanical properties, residual strength, and macroscopic and microscopic failure modes of shale were analyzed. The test results show that the stress–strain curve of the shale gradually shortened with the decrease in the water content in the stage of void compaction and plastic yield, and the peak of the stress–strain curve was continuously enhanced. The water content and the peak intensity exhibited a negative linear correlation. The elastic modulus and water content showed an exponentially decreasing distribution. However, as the water content increased, the decreasing rate became slower, the softening coefficient increased, and the plastic deformation increased. The research results provide basic load parameters for the strength and safety of the casing of an oil layer under fracturing conditions.

As the drilling depth continues to increase, the degree of compaction, strength, and formation pressure of the reservoir rock is also increasing. It is necessary to use super perforating bombs to penetrate the pollution zone, and the combination of super bombs-super target-high confining pressure will increase the difficulty of penetration analysis. In this paper, using LS-DYNA software, combined with the ALE algorithm, taking an oilfield downhole perforation as an example, the HS46 super-strong bullet-gun-liquid-casing-sandstone three-dimensional model is established without confining pressure and 50 MPa confining pressure. By establishing non-reflective boundary conditions, the interference of detonation waves on jet shaping and effects is eliminated; by adjusting the mesh density of key parts and optimizing the mesh coordination between different contact surfaces, numerical distortion is reduced, analysis accuracy is improved, and machine time is reduced. Studies have shown that at 13 μs, the jet energy peak reaches 60 kJ, accounting for 23% of the total energy, and then it decays sharply, and the attenuation is zero at 850 μs; at 16 μs, the jet velocity peaks at 6300 m/s; the penetration depth under 50 MPa confining pressure is 560 mm, which is more It is reduced by 20% without confining pressure. The research in this paper can provide a reference method for the simulation analysis of the downhole super projectile penetrating the high confining pressure super target.

Perforation and fracturing parameters critically influence fracturing effectiveness, yet accurately predicting initiation pressure and fracture width remains challenging. This study establishes a comprehensive rock initiation criterion by integrating the Mohr-Coulomb and tensile truncation criteria, providing key technical support for optimizing perforation design and enhancing hydrocarbon recovery. Using advanced numerical modeling techniques, including ABAQUS Cohesive FEM and the extended finite element method (XFEM), a detailed 3D model of perforated reservoir rock was developed. Based on a case study from Southwest China, the model simulates the entire fracturing process, encompassing fluid injection, fracture initiation, propagation, and in-situ stress redistribution. Key findings demonstrate significant parameter effects. Perforation azimuth (θ) nonlinearly influences fracture propagation, with deflection increasing from 0°to 45°, decreasing from 45° to 90°, and proceeding straight at 90°. A critical perforation depth threshold was identified at 1.4m; beyond this, initiation pressure stabilizes and effectiveness becomes depth-independent. Increasing pump pressure from 80MPa to 95MPa drastically reduced initiation time from 17s to 5s, enhancing fracture efficiency. These results offer practical, quantitative guidelines for optimizing perforation parameters and fracture control, thereby contributing to improved recovery in similar reservoirs.