Nanoparticle Stabilized High Internal Phase CO2-in-Water Foams: Effects of Surfactants and Polymers

Chemical formulations of nanoparticles and surfactants are developed to stabilize high internal phase carbon dioxide-in-water (C/W) foams for low water hydraulic fracturing fluids. Silica nanoparticles and low concentrations of surfactants that weakly interact with nanoparticles were used to stabilize the C/W foams. The surfactants are adsorbed onto the nanoparticles to influence the contact angle of the nanoparticles to stabilize the dispersed CO₂ phase droplets against coalescence. Also, the free surfactants reduce the interfacial tension between the aqueous phase and CO₂ phase to facilitate the break-up of the CO₂ phase into bubbles. The ability to achieve stable high internal phase C/W foams with properly designed nanoparticles could offer an alternative to conventional surfactants to raise the foam stability to be adequate for hydraulic fracturing operations. Further, water-soluble polymers were demonstrated to greatly improve the viscosities of the C/W foams. The ability to generate viscous fluids with low amounts of water for fracturing of shale reservoirs is of great interest for both reducing global water utilization and mitigation of post-processing of contaminated fracturing fluids.