Improving the stability of nitrogen foams using silica nanoparticles coated with polyethylene glycol

Abstract To meet the growing global energy demand, it is necessary to use enhanced oil recovery (EOR) methods to produce fuel from unconventional oil fields. The injection of steam combined with foams as a divergent fluid is one of the techniques proposed as an alternative to improve the production efficiency of heavy and extra heavy oil reservoirs. To achieve this goal, it is necessary to optimize foam stability. This work proposes a technique to improve foam stability using polyethylene glycol (PEG)-coated silica nanoparticles as an additive, which in synergy with a surfactant provide a structural reinforcement of the bubbles to increase their half-life time and durability. For this purpose, four silica nanoparticles with different amounts of surface coating material (i.e. polyethylene glycol) were synthesized by the sol gel method in order to modify their chemical and physical properties. Then, the nanoparticles were characterized to determine properties such as size, point of zero charge, and chemical composition. Nanofluids were obtained by mixing of surfactant solution and nanoparticles. Their corresponding aggregate size and zeta potential were experimentally determined. Subsequently, nanofluids were tested and it was found an increase in the durability of the foam up to 67%. Additionally, adsorption tests were performed to analyze the interactions between nanoparticles and fluids. Moreover, apparent viscosity and the morphologies of the foams were analyzed through microscopic observation of the bubbles to determine changes in their structure. The results show that the diffusion of gas slows down in the presence of nanoparticles and the liquid films between bubbles also become thicker. In summary, the results show that the functionalized nanoparticles could increase the quality of nitrogen foam.