Effect of Boundaries and Injection Rate History on Thermal Signature at Monitoring Wells during CO2 Storage in Saline Aquifers

Carbon dioxide geologic storage (CGS) is identified as technically feasible and economically cost-effective technique to reduce greenhouse gas emissions into the atmosphere. One of the major concerns in relation to CGS projects is CO2 leakage from the subsurface. To assure the containment of the injected CO2, monitoring is essential during and after CO2 injection to track CO2 plume migration. Recently, temperature monitoring has been studied as an alternative to track CO2 plume. Different thermophysical processes associate CO2 flow in subsurface which result in a warming front that moves adjointly with the hydraulic front. In this work, we study the effect of outer reservoir boundary conditions, reservoir size, and injection history on the thermal signature at the warming front, and how this is related to pressure and saturation behavior. A fully coupled wellbore-reservoir model is used to model pressure, temperature, and saturation behavior in the storage reservoir, and within the monitoring wells using two different outer boundary conditions, namely infinite-acting (open) and no-flow (closed). The numerical simulations are done using T2Well-ECO2N simulation tool. Temperature, pressure, and CO2 saturation behaviors are analyzed within the monitoring wells at different levels, and different behavior is obtained compared with the infinite-acting reservoir model. In the closed reservoir model, excessive increase of the temperature is observed due to the adiabatic compression and the increase of the mutual solubility of reservoir fluids which enhances the thermal signature at the plume front. On the other hand, the excessive increase of pressure in closed reservoir increases CO2 density and consequently mitigates the buoyancy effect and decreases the occupied volume of CO2 plume which in turn results in different CO2 distribution and delayed CO2 arrival time at shallow layers compared with the infinite-acting model. Pressure and temperature evolutions as CO2 moves from formation to wellbore are considered in our study. The impact of the injection history on the temperature signal has also been studied. The temperature signal obtained after CO2 arrival is only slightly sensitive to the injection rate history, while the temperature characteristic behavior remains the same regardless of the rate history.