win德赢

Abstract: The low porosity and low permeability of shale remain the primary challenges in shale gas exploitation. Traditional single permeability enhancement techniques have shown limited efficacy, failing to effectively address these technical bottlenecks. This study investigates the synergistic effects of perforation-induced permeability enhancement and acidizing operations on the mechanical properties and micro-pore structure of shale. The improved Split Hopkinson Pressure Bar (SHPB) technique was employed to simulate dynamic impact damage under triaxial stress conditions. Damaged and undamaged rock specimens were immersed in a 15% hydrochloric acid solution to fabricate combined-damage specimens and acid-etched specimens with varying damage states. Uniaxial compression tests, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) were conducted on these specimens. SEM images were binarized, and combined with low-temperature nitrogen adsorption tests, the effects of different damage states on the mechanical behavior, energy dissipation, micro-morphology, and pore characteristics of shale were systematically evaluated. Results demonstrate that the peak stress and elastic modulus of shale exhibit a negative correlation with acid-etching duration. The mechanical properties of combined-damage specimens are inferior to those of pure acid-etched specimens, with the minimum peak stress reaching 147.10 MPa—a 43.53% reduction compared to untreated specimens. The energy dissipation ratio significantly increases, with a maximum value of 34.74%. XRD analysis reveals that prolonged acid immersion effectively reduces the carbonate content in specimens, while composite treatment accelerates the reaction between rock matrix and acid solution. Microstructural characterization indicates that acid etching enhances the porosity of shale, particularly the area of mesopores and macropores, with more pronounced pore development and a fragmented interface structure. These findings deepen the understanding of physical mechanisms during shale gas extraction and provide critical theoretical support for optimizing integrated permeability enhancement technologies.