Mechanistic Modeling of Foam Flow Through Porous Media in the Presence of Oil: Review of Foam-Oil Interactions and an Improved Bubble Population-Balance Model

Abstract

Modeling foam flow through porous media in the presence of oil is essential for various foam-assisted enhanced oil recovery (EOR) processes. We performed an in-depth literature review of foam-oil interactions and related foam modeling techniques, and demonstrated the feasibility of an improved bubble population-balance model in this paper. We reviewed both theoretical and experimental aspects of foam-oil interactions and identified the key parameters that control the stability of foam lamellae with oil in porous media. Upon reviewing existing modeling methods for foam flow in the presence of oil, we proposed a unified population-balance model that can simulate foam flow both with and without oil in standard finite-difference reservoir simulators. Steady-state foam apparent viscosity as a function of foam quality was used to evaluate the model performance and sensitivity at various oil saturations and fluid velocities. Our literature review suggests that, among various potential foam-oil interaction mechanisms, the pseudo-emulsion-film (gas/aqueous/oil asymmetric film) stability has a major impact on the foam-film stability when oil is present. Based on the pseudo-emulsion-film mechanism, we therefore developed a new foam-coalescence function in the population-balance model using the gas-water capillary pressure (Pcgw) in oil-free cases and the pseudo-emulsion capillary pressure (Pcpf) when oil was present. The respective critical values Pcgw * and Pcpf * can be estimated through disjoining pressure measurements. A smooth transition, from no foam destabilization at zero or substantially low oil saturations to no foam beyond a critical oil saturation, was considered for this purpose. The new model was able to handle the extent of the detrimental effect of oil on foam with one adjustable parameter k-2. This work consolidated various findings of foam-oil interactions based on pseudo-emulsion films in the past through a comprehensive literature survey. We have developed a unified model to simulate foam flow in porous media with and without oil using the mechanistic population-balance approach for the first time. This model can therefore be used in foam EOR simulations both in the oil-bearing zones as well as zones with no oil or residual oil present.