Study on CO2 Energized Fracturing in Shale Reservoirs

Supercritical CO₂ (SC-CO₂) shows great potential for application in the development of unconventional oil and gas reservoirs. It not only reduces breakdown pressure but also activates complex fracture networks, thereby enhancing reservoir permeability and effective fracture volume. However, significant differences in fracture morphology are observed under varying injection parameter conditions. This study investigates the mechanisms of SC-CO₂ pre-pad fracturing in shale reservoirs through quasi-triaxial fracturing experiments, focusing on the effects of different fracturing methods on reservoir stimulation. CO₂ fracturing forms a highly complex fracture network with a high fractal dimension, whereas supercritical CO₂ followed by slickwater as the fracturing fluid creates wider and more continuous primary fractures, resulting in larger fracture volumes but lower fracture complexity. The study elucidated the mechanisms of various fracturing fluids by delineating the fracture morphology under different parameters, thereby establishing a theoretical foundation for the parameter design of on-site SC-CO₂ pre-pad fracturing operations.