Effects of Reversibility of Surfactant Adsorption on Surfactant Flooding

The application of surfactant flooding is aimed to reduce interfacial tension (IFT) between aqueous and oil phases to achieve ultra-low condition. By this ultra-low condition, oil can be liberated and consecutively oil recovery is increased. However, surfactant adsorption in porous media as surfactant solution is in contact with reservoir rock surface results in a considerable economical ineffectiveness. This study is proposed to investigate adsorption and desorption mechanisms together with reversibility of surfactant adsorption in static and dynamic tests between Sodium Dodecyl Benzene Sulfonate (SDBS) and Berea sandstone. After that, study of operational parameters including surfactant slug size, surfactant concentration, and surfactant adsorption value is performed in STAR® commercial simulator. Furthermore, degrees of reversibility of surfactant adsorption on operational parameters are evaluated to investigate the effectiveness of this behavior on surfactant flooding. Laboratory experiment results of static tests revealed that adsorption of SDBS onto Berea sandstone obeys Langmuir adsorption isotherm, and the maximum adsorption and desorption values are 90 mg/100g and 27 mg/100g respectively at surfactant concentration of 1.0 %wt. However, different adsorption-desorption values are observed in dynamic tests on 1.0 %wt. concentration, which are 57.65 mg/100g and 47.86 mg/100g respectively. Study of the effects of reversibility of surfactant adsorption on interested operational parameters revealed that the best additional oil recovery is obtained from bigger injection slug with concentrations other than the maximum adsorption concentration. In case of fixed injection mass, larger slug size with less concentration for small surfactant amount, and smaller slug with higher concentration for large surfactant amount are preferred. Implementation of surfactant flooding with consideration on effects of reversibility should be performed at concentrations other than the maximum surfactant adsorption concentration with bigger slug size. Moreover, small slug size is suitable for high adsorption reservoir, while larger slug is preferred in case of low adsorption rock surface.