Parameter Optimization of Pre-stage CO₂ Fracturing

As a core technology for the efficient and green stimulation of unconventional oil and gas reservoirs, pre-stage carbon dioxide (CO₂) fracturing relies on the unique properties of CO₂ including low viscosity, high diffusivity, easy phase transition, and energy enhancement for flowback improvement. It can effectively reduce reservoir breakdown pressure, activate natural fractures, mitigate water-sensitive formation damage, and facilitate carbon sequestration. However, current field applications are constrained by several critical issues, such as poor matching of injection parameters, insufficient accuracy in fracture network regulation, difficult wellbore phase-state control, and an imbalance between cost and benefit, which severely restrict its stimulation potential. Based on the fundamental mechanisms of pre-stage CO₂ fracturing, this paper systematically analyzes the key influencing factors for process optimization. Combined with the petrophysical properties of shale oil reservoirs in Sichuan, the CO₂ injection volume and rate are optimized, providing theoretical support for the efficient development of this block.