Study on Fracture Propagation Patterns of Supercritical CO₂ Fracturing in Perforated Wells Based on Displacement Discontinuity Method

A thermo-hydro-mechanical coupled fracture propagation model was developed by incorporating the temperature- and pressure-dependent physical properties of CO₂ and a tensile-shear mixed-mode fracture propagation criterion. The model equations were solved numerically using the displacement discontinuity method. Comparisons with the traditional two-dimensional Khristianovic-Geertsma-Deklerk(KGD) analytical model and conventional hydraulic fracturing were conducted to investigate the effects of perforation angle, in-situ stress difference, injection flow rate, and formation temperature on fracture propagation behavior. The results demonstrate good agreement between the proposed model and KGD analytical solutions. Compared to conventional hydraulic fracturing, supercritical CO₂ fracturing generates fractures with greater length but narrower width. Increasing the perforation angle results in significant compression of fractures near the wellbore, reduced fracture width, and notable fracture deflection; fracture deflection angles of 12.71° and 71.34° were observed at perforation angles of 15° and 90°, respectively. As the horizontal stress difference increases, fracture deflection angles also increase; with a maximum horizontal principal stress of 30 MPa and minimum horizontal principal stresses of 10 MPa and 25 MPa, fracture deflection angles reached 90.00° and 77.74°, respectively, accompanied by reduced fracture apertures. Higher injection flow rates increase net fracture pressure, enhancing the compressive effect of supercritical CO₂ on fractures and promoting the formation of high-quality fracture networks with longer lengths and larger apertures. Elevated formation temperatures result in decreased fracture inlet widths and increased fracture lengths. These findings contribute to advancing supercritical CO₂ fracturing technology development.