Characterization of Anionic–Nonionic Surfactant Mixtures for Enhanced Oil Recovery

Enhanced oil recovery (EOR) has been one of the favorable methods in improving oil recovery and extending the production time. One of the techniques used in enhanced oil recovery (EOR) is gas flooding, because of the gases sweeping ability to displace the oil into the production well. Unfortunately, the gas injection method causes severe gas fingering because of the higher mobility and lower viscosity and density of the gas, compared to oil, which creates uneven fluid dispersion (fingering). Thus, a stabilized surfactant foam is introduced to control the injected gas mobility. This paper aims to characterize how the blends of non-anionic and anionic surfactants could act as foam stabilizing agents and to provide a brief exploration on their ability to improve the gas flooding process. The foamability and foam stability of single and mixed surfactant were tested at ambient and elevated temperature; additionally, a salt tolerance study was performed to identify the capability of the foam to withstand real reservoir conditions. Two anionic surfactants: sodium dodecyl sulphate (SDS) and alpha olefin sulfonate (AOS) and one non-ionic surfactant, octyl phenol ethoxylate (TX-100), were used in the study. Each single surfactant was tested for its viscosity and surface tension at the air/water interface under ambient conditions and compared with the mixed surfactants. Data has shown that blending of anionic and non-ionic surfactants has contributed to lower IFT compared to the individual surfactants and to increase viscosity, which is an early indicator of good foam stabilizer for foam flooding, which may lead to oil recovery improvement. The mixture of non-ionic and anionic surfactants, particularly TX-100 and AOS, showed better foamability and foam stability at elevated temperature than the individual pure surfactants.