Geological Sequestration of CO2 in Mature Hydrocarbon Fields. Basin and Reservoir Numerical Modelling of the Forties Field, North Sea

Abstract : Numerical modelling is likely the only available tool to evaluate and predict the fate of CO2 injected in deep geological reservoirs, and particularly in depleted hydrocarbon fields. Here we present a methodology which aims at evaluating the geological leaking risk of an underground storage using a depleted oil field as the host reservoir. The methodology combines basin and reservoir scale simulations to determine the efficiency of the storage. The approach was designed for the study of the reservoir after the injection of CO2 and then does not take into account any CO2 injection period. The approach was applied to the Forties field (North Sea) for which CO2 behaviour was simulated for a 1000 y time period. Our findings suggest that local geological conditions are quite favourable for CO2 sequestration. Possible residence time of CO2 will be in the order of thousands of years and, thus such geological depleted hydrocarbon fields storage is probably a good alternative for a long term CO2 sequestration. Additionally, results of this work can help to establish criteria to identify other mature hydrocarbon fields aimed for CO2 sequestration.