The design of nitrogen foams with longer lifetimes would enable more effective gas mobility control and raise the sweep efficiency in enhanced oil recovery (EOR). The objectives are to show that foams formed with functionalized nanoparticles (NPs) and surfactants are more stable than foams stabilized with surfactants alone in porous media, and to explain the behavior in terms of interfacial properties. The covalent surface modification of 20 nm silica NPs with low MW ligands provided: (1) colloidal stability in concentrated brine and elevated temperatures (up to 90°C) and (2) nanoparticle adsorption at the interface to enhance foam stabilization. In order to achieve these goals, surfactants were chosen strategically for the desired interactions with the nanoparticles.<br/>The nanoparticle surface chemistry and high salinity led to weakly attractive interactions between NPs resulting in weak elastic gels, as characterized by a high surface dilational elasticity. These properties were improved with surfactants to further reduce the interfacial tension and increase the surface dilational elasticity. With these properties foams could be generated with a small minimum pressure gradient. As a result, viscous foams were generated under 3000 psia up to 90 °C with superficial velocity below 10 ft/day in core flood experiments with beadpacks. A high dilational modulus indicated strong adsorption of nanoparticles/surfactant. These properties reduced lamellae drainage and enhanced foam stability against coalescence and coarsening with negligible changes in foam bubble size over 24 hours.<br/>The emerging understanding of how to design colloidally stable functionalized nanoparticles in concentrated divalent brines with strong adsorption at the gas-brine interfaces will advance the design of highly stable foams. The development of mechanistic insight from the NP surface chemistry to the interfacial properties to foam stability in porous media is of great interest for designing formulations to improve the sweep efficiency in EOR.

Ultra-stable nitrogen-in-brine foams with the surface-modified silica nanoparticles in presence of surfactants for enhanced oil recovery

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.