Mixture of Anionic Surfactant and Surface-Modified Silica Nanoparticles for Enhancing Foam Stability

Foam is one of the most promising techniques to reduce gas mobility in subsurface formations. Foamed-gas injection can reduce the mobility of gas by increasing the volume of trapped gas in the liquid phase, thereby increasing its apparent viscosity to reduce the relative permeability. However, the poor stability of foam generated by surfactants at reservoir conditions is a challenge that hinders the effectiveness of the foam flooding. The mixture of surfactant and nanoparticles can offer a potential solution to enhance foam stability. The objective of this study is to evaluate how such new mixtures formulated in this work enhances the foam stability. Foam analysis using foam analyzer equipment and nanoparticle size measurements, were conducted to capture the foam stability and strength for an anionic surfactant and the mixture of an anionic surfactant and surface modified silica nanoparticles. Also, transmission electron microscopy (TEM) was used to assess and visualize the surfactant-nanoparticles interactions using different concentrations of the nanoparticles. The results from the experiments demonstrated that the use of surfactant combined with nanoparticles enhances the stability and strength of the generated foam when compared to the use of surfactant alone. Comparative images of bubble count and structure of the foams generated showed higher bubble count with smaller bubble sizes when the surfactant is mixed with the nanoparticles. The higher bubble count and smaller bubble sizes are indicative of better, stronger and more stable foams. TEM images showed that the nanoparticles have a tendency to form layered structures in the solutions. This formed layer enhances the film stability by delaying the liquid film rupture. The combination of nanoparticles and surfactant serves as a new technique for generating stronger and stable foams in gas mobility control applications. This study also provides an important learning point that the selection of the right surfactant and nanoparticle combination are the keys to generate more stable foams.