The Synergy of Surfactant and Nanoparticles: Towards Enhancing Foam Stability

Abstract

Gas injection has been widely used for enhancing oil recovery in petroleum reservoirs. One of the major challenges facing this technique is the high mobility of gas caused by its lower viscosity compared to reservoir fluids. Injecting the gas in a foam phase can solve the mobility challenge by increasing the gas apparent viscosity. Surface active agents such as surfactants are usually used to generate foams. However, the long-term stability of the surfactants is challenging. The synergistic effect of surfactants and nanoparticles may offer a novel technique to solve the foam stability issue and generate stronger foams. This study evaluates the role of nanoparticles on stabilizing surfactant foams in porous media. Anionic surfactant and surface modified silica nanoparticles were used in this assessment. Dynamic foam tests were conducted to study the foam stability and strength in porous media. The major parameter used to evaluate the foam strength in this study is the mobility reduction factor (MRF). The experiments were conducted using nitrogen gas at elevated pressure. The influence of nanoparticles on surfactant foam strength was conducted at different nanoparticles concentrations and fixed surfactant concentration. The results demonstrated that the presence of nanoparticles in surfactant solution resulted in a more stable foam compared to surfactant alone. The nanoparticles used in this study seem to enhance the foam stability by either one or two mechanisms: particle arrangement during film drainage or increasing the capillary pressure of coalescence. Based on the dynamic foam tests, higher pressure drops were reported for the mixtures of nanoparticles and surfactant compared to surfactant alone. This clearly indicated the higher resistance to gas flow caused by the foam generated using the mixture. The results also showed that as the nanoparticles concentration increased, MRF increased, too. The MRF for the sample contains only surfactant was 72. However, the addition of 0.50 and 1.00 wt% of nanoparticles to the surfactant solution resulted in higher MRF: 75 and 85, respectively. The need for generating strong foam is very important to ensure the long term stability of foam and, consequently, reducing the gas mobility in porous media. The addition of solid nanoparticles to surfactant solutions might strengthen the aqueous film between gas bubbles and, eventually, enhancing the foam stability.