Experimental Study on Fracture Propagation of Tight Sandstone Under the True Triaxial Fracturing with Supercritical CO2

Supercritical CO2 fracturing is a novel fracturing technology that boasts significant benefits, including the reduction of reservoir pollution and the achievement of thorough backflow following the fracturing process. Guided by the “dual carbon” goal, supercritical CO2 fracturing technology has broad application prospects. Due to the limited research on the fracture propagation law of tight sandstone in the Sichuan Basin by supercritical CO2, it cannot effectively guide the development of supercritical CO2 fracturing plans. Based on the true triaxial fracturing simulation experimental system, experimental research on supercritical CO2 fracturing of tight sandstone was conducted to study how fracturing fluid type, displacement, and horizontal stress difference affect the fracture propagation law. The research shows that: First, the fracture pressure of supercritical CO2 is 9.5 MPa lower than that of slick water, with an average decrease of 40.6%, and the rock fracture time increases by 274.1%. The fracture tortuosity and fracture surface roughness are larger, and the fracture network is more complex, which can provide more effective percolation channels for the formation fluids. Second When the injection rate of supercritical CO2 increases from 30 mL/min to 60 mL/min, the fracture pressure increases by 26.5%, the fracture time decreases by 43.3%, the number of branch fractures increases, and the angle between branch fractures and main fractures increases. Third, When the horizontal stress difference increases from 6 MPa to 10 MPa, the fracture pressure increases by 31.4%, and the fracture time decreases by 7.5%. The fracturing fracture (HF) mainly extends along the direction of the maximum horizontal principal stress, which is not conducive to multi-point fracture initiation and fracture turning. This study clarified the influence of different fluids, displacement, and stress differences on the propagation of tight sandstone fractures through a large-scale true triaxial fracturing experimental device, providing a strong theoretical basis and experimental support for CO2 fracturing and on-site CO2 storage in tight sandstone gas reservoirs.