Experimental Investigation of Thermal Stress Effects from Supercritical CO₂ Injection on Rock Properties in Naturally Fractured Carbonate Reservoirs

Carbon dioxide (CO₂) injection into subsurface formations is a promising strategy for mitigating greenhouse gas emissions. However, thermal stress resulting from temperature differences between the injected fluid and the reservoir rock can significantly alter formation properties. This study presents a comprehensive experimental investigation into the effects of thermal stress induced by supercritical CO₂ injection on the petrophysical and geomechanical characteristics of carbonate rocks in naturally fractured reservoirs. Using core flooding, uniaxial compression tests, nuclear magnetic resonance (NMR), and porosity/permeability measurements, the impact of varying injection pressures (10–25 MPa) and temperatures (40–70°C) was evaluated. Results show that porosity increased by 13–61% and permeability by 20–384%, depending on the conditions. Thermal stress led to microfracturing, reduced uniaxial compressive strength, and altered pore size distribution. These findings underscore the importance of optimizing CO₂ injection parameters to enhance storage efficiency and maintain caprock integrity in deep geological formations.