We show experimentally that surface treated silica nanoparticles greatly enhance the thermodynamic stability of CO2-foam compared to other foam stabilizers at elevated temperatures and salinities in the presence of oil. The aqueous nanofluid mixes with CO2 in the porous media to generate CO2-foam for enhanced oil recovery by improved sweep efficiency, resulting in reduced carbon footprint from oil production. Our results show that surface modified nanoparticles are able to stabilize CO2-foam at elevated temperatures and extreme brine salinities, and demonstrate that nanoparticle injection for improved CO2-foam mobility is an upcoming CCUS technology for mature fields. New experimental results show that 1) nanofluids remain stable at extreme salinities (up to 25 wt% TDS) with the presence of both monovalent and divalent ions; 2) both pressure gradient and incremental oil recovery during tertiary CO2-foam injections were 2 - 4 times higher with nanoparticles compared to no foaming agent; 3) CO2 stored during CCUS with nanoparticle stabilized CO2-foam increased by over 300% compared to co-injections without nanoparticles.

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