Surfactant flooding: The influence of the physical properties on the recovery efficiency

Enhanced Oil Recovery (EOR) processes aim at increasing the performance and operative life of oilfields while newer, greener and more efficient energy sources are developed. Among the chemical EOR techniques, surfactant flooding is one of the most well-known methods, applied mainly in low- and medium-viscosity oilfields. Surfactants diminish the interfacial energy between the oleous and aqueous phases, reducing the forces responsible of the capillary trapping phenomenon and mobilizing the remaining oil. This paper presents the study of a novel two-dimensional surfactant flooding simulator for a four-component (water, petroleum, chemical, salt), two-phase (aqueous, oleous) system in porous media. It is aimed mainly at discussing the influence of the physical phenomena present in the reservoir during the recovery, namely: rock compressibility, diffusion, capillary pressure and adsorption. The system is numerically solved using a second-order finite difference method using the IMPEC (IMplicit Pressure and Explicit Concentration) scheme. The oil recovery factor was negatively affected when these phenomena were considered, being strongly sensitive to the adsorption. The other phenomena decreased the efficiency of the process to a lesser extent, whilst the capillary pressure did not affect significantly the flooding performance. The presence of salt in the reservoir rendered the adsorption process more relevant, with water-in-oil emulsions being more sensitive to the presence of this fourth component. This paper shows the importance of the design and optimization of chemical agents to be used in EOR before its field application.