Enhancing N2 and CO2 foam stability by surfactants and nanoparticles at high temperature and various salinities

To keep up with the ever-growing global energy demand, the petroleum industry has shifted its attention to enhanced oil recovery (EOR) methods, which ensure 30%-60% of residual oil recovery following primary and secondary recovery processes. Foam injection is one of these methods. Due to their low sensitivity to gravity and permeability heterogeneities which improve sweep efficiency, foams are preferable injection fluids than water or gas. However, this recovery technique is not widely used due to the thermodynamic instability of foams. This work aims to take advantage of recent breakthroughs in nanoparticles engineering to build long-lasting nanoparticle-stabilized foams, as nanoparticles can withstand high temperatures and reservoir conditions for a prolonged time. Therefore, to achieve this goal, a comprehensive set of screening experiments was conducted, which included an investigation of the influence of ionic surfactants on foam stability with and without silica nanoparticles at room and elevated temperatures, as well as bulk foam tests with air, nitrogen, and CO2, characterization of foaming suspensions, and analysis of foam texture and morphology. The half-life duration, foam quality, and foam composite index were used to determine the stability of the generated foams. The findings demonstrated that the addition of 0.05% silica nanoparticles could improve the half-life of nitrogen and CO2 foam up to 13% and 40%, respectively. However, the extent of this depends on temperature, salinity and optimal concentration of nanoparticles. Furthermore, the results showed that optimal concentrations of nanoparticles and surfactants should be carefully determined in order to achieve a positive synergistic effect. Results illustrated that selected nanoparticles-surfactant formulations appear very promising for EOR as they show high stability at elevated temperatures and tolerance to different mineralization.