Study on Adaptability of Supercritical CO₂ Fracturing on Reservoir Permeability

To investigate the adaptability of supercritical CO₂ fracturing to reservoir permeability, this study conducted supercritical CO₂ fracturing experiments on tight sandstone samples with different permeabilities (0.08~1.0 mD). The characteristics of induced fractures were quantitatively analyzed using CT scanning, and the experimental results were validated and supplemented through field-scale numerical simulations. The results show that supercritical CO₂ can effectively fracture rock samples with permeabilities in the range of 0.08~0.3 mD. As permeability increases, the complexity of induced fractures decreases, and the fracture volume reduces. When the permeability exceeds 0.5 mD, supercritical CO₂ fails to fracture the rock, whereas hydraulic fracturing remains effective, primarily due to differences in fluid properties. Numerical simulations validated the experimental findings, indicating that supercritical CO₂ can successfully fracture reservoirs with different permeabilities under field conditions, but the fracturing effectiveness varies significantly. As reservoir permeability increases (0.01~100 mD), parameters such as fracture half-length, width, height, fractal dimension, and filtration area decrease, while fluid loss gradually increases, leading to a decline in fracturing effectiveness. The study demonstrates that supercritical CO₂ is more suitable for low-permeability reservoir stimulation, and parameter optimization is required during operations to adapt to reservoirs with different permeabilities. This research provides a theoretical foundation for the design of supercritical CO₂ fracturing operations in unconventional reservoirs.