New insight into foam stability enhancement mechanism, using polyvinyl alcohol (PVA) and nanoparticles

Foam stability is critical when using foams to reduce the gas mobility and to increase the oil sweep efficiency, under harsh reservoir conditions. In this paper, we formulated foam stabilizer including a polymer, two different surfactants, and six different nanoparticles. Static foam stability tests were conducted using alpha olefin sulfonate (AOS) and cetyltrimethylammonium bromide (CTAB) as anionic and cationic surfactants, respectively; polyvinyl alcohol (PVA) polymer; and six acidic and amphoteric nanoparticles. We also tested the effect of oil on the foam stability, using a light and a heavy crude oil where NaCl brine was the aqueous phase. The effects of different stabilizer formulations, experimental variables, and their interactions were also evaluated. To assess the effectiveness of foam stabilizers, supplementary measurements were measured, including the dynamic interfacial tension, the viscosity of the aqueous solutions, the foam comprehensive index (FCI), and the diffusivity of the nanoparticles in liquids. The results indicated a significant effect of the polymer on the foam stability; when the PVA polymer was added to the foam solution containing an anionic surfactant and acidic nanoparticles, a third protective layer was formed, stabilizing the lamella. The most stable foam was obtained by using moderate concentration of Al2O3 nanoparticles in a solution with low concentration polymer and NaCl brine. This foaming solution featured over 16 times higher half-life time, t(1/2), compared to the nanoparticle-surfactant system alone. It was found that the heavy oil destabilizes the foam more than the light oil; also, an increase in the salinity of the aqueous phase increased the foam stability, when other factors were fixed. This research work provides useful tips to create stable foams through using nanoparticles and polymer that can have various applications in energy and environment processes. (C) 2020 Published by Elsevier B.V.