基于ScCO2-水耦合作用的页岩微观力学特性分析OA

Supercritical carbon dioxide(ScCO2)technology has emerged as an advantageous solution for the green and efficient development of shale gas due to its significant advantages,such as effective frac-turing for production enhancement and effective protection of reservoirs.To investigate the influence of ScCO2-water coupling on the micromechanical properties of shale,outcrop samples from the Longmaxi Formation in the Sichuan Basin were subjected to drying,water-wet,and ScCO2-water coupling condi-tions.The elastic modulus and hardness were obtained through nanoindentation continuous stiffness measurement tests,and the fracture toughness was determined based on energy analysis and scanning e-lectron microscopy observations.The correlations among various micromechanical parameters were ana-lyzed.Combining X-ray diffraction and scanning electron microscopy,the influence patterns of mineral composition on mechanical properties were revealed.The results indicate that both water-wet and Sc-CO2-water coupling cause significant elastic deterioration to shale.The reductions in elastic modulus,hardness,and fracture toughness are more pronounced under ScCO2-water coupling,with decreases of 14.01％,20.99％,and 16.30％,respectively.Both theoretical derivation and experimental fitting dem-onstrate a consistent linear positive correlation among elastic modulus,hardness,and fracture tough-ness.The Longmaxi Formation shale exhibits a high proportion of brittle minerals.ScCO2-water cou-pling induces dissolution and precipitation of calcareous and siliceous minerals,leading to intensified ma-trix damage,decreased elasticity index,and increased brittleness index.These findings provide a refer-ence for characterizing the micromechanical properties of shale and designing CO2 enhanced recovery measures.