Thermal Signature of Free-Phase CO2 in Porous Rocks: Detectability of CO2 by Temperature Logging

This study examines the suitability of thermal methods, especially DTS (Distributed Temperature Sensing) cables (in the annulus or behind casing) to monitor the fate of injected CO2 for emissions reduction purposes. The static temperature signal of CO2 stored in pores of sandstone and claystone examples is calculated as a function of porosity, CO2 saturation, and CO2-filled reservoir thickness. The dynamic temperature signal associated with the movement of CO2 in the well and the porous rock is discussed and results of numerical simulations are presented. The detectability of these temperature signals is assessed and found to be useful in detecting leakage over short time intervals and saturation changes in the storage reservoir over the longer term.