Enhancing CO2-Foam Stability and Rheology Using Surfactants Mixture

Abstract

AbstractGenerating in-situ foam is regarded as one of the most promising techniques to overcome gas mobility challenges and, accordingly, improve sweep and sequestration efficiency in CO2 injection processes. Foam generation and stabilization at harsh reservoir conditions as well as surfactant-rock interactions are the major limiting factors that can impair the efficiency of foam flood. Surfactants mixtures offer the solutions necessary for the generation and stabilization of foams at harsh reservoir conditions.In this study, mixtures of anionic and amphoteric surfactants have been evaluated in comparison to using each surfactant individually to determine the overall effect on producing stable foams. Using bottle foam tests, dynamic foam analyzer, and foam rheology apparatus, the foam stabilization factors were analyzed and quantified. The bulk foams for each surfactant and the mixture of the two surfactants at different mixing ratio were analyzed by measuring the foam-life over time, the foam bubble sizes, and the foam rheological properties at high pressure, high temperature (HPHT) and using high salinity water.The experimental results clearly demonstrated that the use of surfactant mixtures improved the stability of produced foam. The results revealed that the mixing ratio of each surfactant significantly impacts the foam stabilization. The surfactant mixture solutions produced more stable foams as evidenced by a longer foam-life. The foam-life increased by almost 1.5-2 times depending on the mixing ratio. The results also revealed that there are ranges of concentrations at which the most stable foams can be produced. The foam rheology results showed that the produced foams using the surfactant mixtures are of higher apparent viscosity when compared to those obtained with the anionic surfactant. The addition of the amphoteric surfactant to the anionic surfactant solution enhanced the foam stability, and accordingly, the foam rheological properties. The measured foam apparent viscosity increased as the concentration of the amphoteric surfactant increased. Longer foam-life and greater apparent viscosity are indicative of better, stronger and more stable foams.