Immiscible foam displacement in low-permeability formations: A numerical study for screening potential reservoirs

Understanding immiscible displacement in low-permeability porous media such as tight oil reservoirs, requires further studies. In this work, we explore the governing mechanisms during immiscible displacement of oil phase by an aqueous foam in low-permeability formations. An implicit pressure explicit composition numerical model coupled with a local equilibrium foam model (IMPEC-LE) is developed to study the performance of both immiscible CO2 and CO2-foam injection into low-permeability oil formations. Results show that at very low permeability the injectivity of an aqueous surfactant is very poor and therefore the displacement efficiency with foam is low. We found this permeability limit is approximately 0.1 mD and permeabilities below this can be quickly screened as unfavourable to foam injection. For permeabilities greater than 0.1 mD, foam injection always yields higher oil displacement efficiency than immiscible gas injection. It was shown that lower foam quality, has the tendency to increase the displacement efficiency by ensuring foam stability in the formation resulting in later gas breakthrough. The outcome of this study can be used to screen the applicability of foam in a foam-assisted displacement process to maximise the displacement efficiency and reduce the cost and environmental footprints associated with oil recovery processes.