Effects of supercritical CO₂/water imbibition under dynamic pressures on shale mechanics and acoustic emission characteristics

•The effects of supercritical CO2 and water immersion on the mechanical properties of shale under different dynamic pressures are investigated.•The strength and Young's modulus of shale are decreased more significantly after water immersion compared to supercritical CO2 immersion.•Compared with the constant pressure imbibition, the dynamic pressure imbibition changes the microstructure of shale and weakens its mechanical properties more significantly.