Experimental Study of Supercritical CO2 Dual-Well Fracturing under the Effects of High Temperatures and In Situ Stress Differentials

Abstract Supercritical CO2 (SC–CO2) dual-well fracturing is a key technology for the development of deep tight reservoirs, where fracture propagation is predominantly influenced by the coupled effects of high temperature and in situ stress. To address the lack of systematic experimental investigations under high-temperature conditions up to 200 °C and true triaxial stress states, this study conducts sequential dual-well fracturing experiments on artificial tight sandstone samples under combined high-temperature and differential horizontal stress conditions using a true triaxial loading system. Three-dimensional (3-D) fracture networks are quantitatively reconstructed, and injection pressure responses are analyzed through an integrated approach combining computed tomography scanning with U-Net-based intelligent image segmentation. The results show that elevated temperature significantly enhances interwell fracture synergy: at 200 °C, the fractal dimension of the fracture network increases by 37% and fracture volume by 60% compared to 25 °C, with markedly improved connectivity between the two fracturing stages. In contrast, increasing the horizontal stress differential inhibits fracture network complexity, reducing the fractal dimension by approximately 5% per unit increase in stress differential. A theoretical model of fracture propagation is developed, demonstrating that high temperature does not merely reduce wellbore interference passively but actively promotes fracture deflection and branching by inducing thermal gradients that substantially increase the ratio of Mode I to Mode II stress intensity factors, thereby facilitating efficient interstage connection of fracture networks. Moreover, SC–CO2 exhibits clear advantages over water-based fracturing fluids in generating complex fracture networks, achieving a 59% higher fracture volume under identical experimental conditions. This study provides essential experimental data and theoretical insights for optimizing fracturing parameters and engineering designs in SC–CO2 dual-well and multiwell applications within deep tight reservoirs.