Effects of Injection Temperature and Well Connectivity on Reservoir Stability and Storage Efficiency in Shale Formations.

The deployment of CO2 injection in shale reservoirs for simultaneous carbon sequestration is constrained by complex thermo-hydromechanical (THM) coupling effects. This study establishes a fully coupled two-dimensional numerical model to systematically investigate the multifield evolution and system stability under varying CO2 injection temperatures and well connectivity configurations. Simulation results demonstrate that good connectivity fundamentally dictates the fluid migration path: while fracture connections significantly enhance the CO2 sweep efficiency by creating preferential flow paths, they concurrently induce stress corridors, amplifying stress concentrations and posing risks to wellbore integrity. Regarding thermal effects, lower injection temperatures accelerate plume propagation and improve immediate sequestration rates in connected fractures but induce severe thermal shocks that threaten the stability of monitoring wells. Conversely, higher injection temperatures mitigate thermal stress and enhance long-term structural stability, albeit with reduced diffusion efficiency. The study reveals a critical trade-off between sequestration efficiency and reservoir-wellbore stability, governed by the synergistic interaction of thermal gradients and hydraulic connectivity. These findings provide theoretical support for optimizing injection temperatures and well deployment strategies to ensure safe and efficient sequestration of CO2 in shale resources.