An Integrated Model for Cold CO2 Injection: Non-Isothermal Compositional Fluid Flow, Geomechanics, with Fracture Propagation

This study develops an integrated thermo-poro-elastic hydraulic fracturing and multiphase compositional flow simulator to evaluate cold CO2 injection. The model captures CO2 phase transitions, thermal stress effects, and fracture propagation dynamics, offering critical insights into injectivity, caprock integrity, and storage efficiency for stable subsurface carbon sequestration. The simulator integrates hydraulic flow and geomechanics with an equation-of-state (EOS)-based energy balance to capture temperature variations. It simultaneously computes thermo-poro-elastic stress, deformation, and fracture propagation. The model is validated against an analytical solution for 1D advection-conduction heat exchange, which was previously validated for the black oil model. While the compositional model captures the expected trend, it is much more accurate than the analytical solution due to EOS-based variations in fluid heat capacity and density, highlighting the importance of dynamic numerical evaluation of these fluid properties. A case study examines cold CO2 injection into shale to assess thermal-induced fracturing risks and seal integrity. The model successfully captures thermal stress evolution and fracture propagation trends, demonstrating the influence of fluid temperature variations on reservoir behavior. In the shale case, high bottom-hole pressure (BHP) initially dominated fracture growth, but cold CO2 injection reduced stress over time, affecting fracture development. The results underscore the need for numerical modeling to capture complex thermo-mechanical interactions beyond analytical approximations. This study presents a first-of-its-kind simulator that integrates temperature-sensitive CO2 phase transitions, thermal stresses, and fracture propagation at a field scale. The insights inform optimized injection strategies that balance injectivity and storage security, contributing to the development of safe, high-efficiency CO2 sequestration technologies.