Abstract: The tight sandstone reservoirs in the Ordos Basin have a series of problems, such as poor physical properties, large burial depth, high clay mineral content, and great difficulty in post-pressure drainage. CO₂ fracturing has advantages such as reducing rock breakage, reducing fluid loss and promoting backflow. It is targeted for reservoirs with poor physical properties, high clay content and low pressure coefficient. Therefore, based on the true triaxial simulation of the fracturing modification problem of tight sandstone under three different injection methods: CO₂ pre-injection, CO₂ foam injection, and CO₂ companion injection. The variation law of core fracture pressure and fracture distribution characteristics of tight sandstone reservoirs under different injection methods were analyzed through the similarity criterion, and the difference analysis of core fracturing results under different conditions was compared. And based on the Petrel geological fracturing integrated platform, the numerical simulation study of reservoir fracture propagation under different CO₂ fracturing modes was simulated. It can be known through quantitative experimental analysis that hydraulic fracturing pressure breaking > CO₂ foam > CO₂ injection > CO₂ preinjection. Compared with hydraulic pressure cracks, the CO₂ pre-pressure crack network is the most complex, followed by CO₂ foam, and finally CO₂ injection. The numerical simulation results match it. The variation law of reservoir fracture network parameters with fracturing operation parameters under different injection methods has been clarified. Its understanding provides operational guidance and suggestions for the efficient development of tight sandstone.

Key words: True triaxial；CO₂ pre-injection, CO₂ foam, CO₂ injection