Speaker
Description
Supercritical CO2 fracturing is expected to create more complex fracture networks than water-based counterparts, thereby improving the permeability and heat extraction in geothermal reservoirs. The underlying fracture mechanisms driven by this low-viscosity fluid may differ from conventional hydraulic fracturing. In this study, we develop a stabilized hydromechanical phase-field fracture model to simulate hydraulic fracturing in two- and three-dimensional polycrystalline microstructures. To address numerical instabilities caused by strong heterogeneity and operator splitting, we propose a novel spatial stabilization term for the monolithic solution of the coupled hydromechanical problem. We then conduct numerical simulations of hydraulic fracture evolution considering rock microstructure under water and supercritical CO2 injection. Our numerical results reproduce laboratory observations and demonstrate that the generation of complex fracture networks is controlled by both rock heterogeneity and fracturing fluid. Our findings further confirm that supercritical CO2 fracturing is more likely to trigger remote activation of heterogeneous interfaces, leading to more complex fracture morphologies.