Monitoring CO2 injection and retention in steam-assisted gravity drainage (SAGD) operations

Abstract

CO2 co-injection can be used to lower the energy requirements for heavy oil recovery in thermal oil operations. Technologies, including steam-assisted gravity drainage (SAGD) for the extraction of bitumen from oil sands, have the potential to improve the energy efficiency and economics of heavy oil production as well as provide an opportunity for carbon retention in the reservoir to offset CO2 return to the atmosphere and reduce greenhouse gas (GHG) emissions. Here, we report a geochemical approach that was developed to monitor the fate and transport of CO2 in the subsurface for a SAGD CO2 co-injection pilot program. Using δ13C–CO2 values from the injection well and other monitoring wells, a Bayesian state space model was used to evaluate the dynamic relationship between co-injection and reservoir CO2 rebound to baseline. The model provides simultaneous estimates of the isotopic changes in CO2 during co-injection, between injections, as well as between sampling events. The results suggest CO2 co-injection could be a viable step towards GHG reduction on a path to net zero emissions.