Laboratory-to-Field Scale Numerical Investigation of Enhanced Oil Recovery Mechanism for Supercritical CO 2 -Energized Fracturing

This study systematically performs multi-scale numerical investigation of supercritical CO 2 -energized fracturing, widely employed for enhanced oil recovery (EOR) in tight oil and gas reservoirs. Two distinct models, spanning from core scale to field scale, are designed to explore the diffusion patterns of CO 2 into the matrix and its impact on crude oil production at varying scales. The core-scale model employs discrete grid regions to simulate the interaction between fractures and the core, facilitating a comprehensive understanding of CO 2 diffusion and its interaction with crude oil. Based on the core-scale numerical model, the wellbore treatment process is simulated, investigating CO 2 distribution within the core and its influence on crude oil during the well treatment phase. The field-scale model employs a series of grids to simulate fractures, the matrix, and the treatment zone. Additionally, a dilation model is employed to simulate fracture initiation and closure during CO 2 fracturing and production processes. The model explores CO 2 diffusion and its interaction with crude oil at different shut-in times and various injection rates, analyzing their impact on cumulative oil production within a year. The study concludes that during shut-in, CO 2 continues to diffuse deeper into the matrix until CO 2 concentration reaches an equilibrium within a certain range. At the core scale, CO 2 penetrates approximately 4 cm into the core after a 15-day shut-in, effectively reducing the viscosity within a range of about 3.5 cm. At the field scale, CO 2 diffusion extends up to approximately 4 m, with an effective viscosity reduction zone of about 3 m. Results suggest that, theoretically, higher injection rates and longer shut-in times yield better EOR results. However, considering economic factors, a 20-day shut-in period is preferred. Different injection rates indicate varying fracture conduction capabilities upon gas injection completion.