Detecting CO2 leakage around the wellbore by monitoring temperature profiles: A scoping analysis

Leakage through abandoned wells represents one of the greatest risks to secure storage of CO2 in geologic formations. In this work, we evaluate the feasibility of using temperature as an indicator for detecting leakage in and around wellbores. Numerical simulation tools are used to simulate temperature propagation both along and around the wellbore when leakage occurs. Typical overall heat transfer coefficient of formation rock is applied to quantify heat dissipation from the fluids leaked in well. We have tested the cases of CO2 phase only and the mixture of CO2 and brine. Thermodynamic phase change of CO2 throughout the wellbore depth is accounted by an equation-of-state. Both vertical and slant (off-shore) wells are examined. Our results indicate that strong temperature variation is observed within 100 m from borehole and then virtual hot layers circulating the fluid column within 3 m radius are formed. However, differences from the ambient temperatures are not significant. The hot CO2 column loses heat in 70 m of well depth from reservoir compared to 50 m height in the case of CO2/brine mixture.