Here we present a comprehensive experimental investigation on the use of nanoparticles as foam stabilizers during co-injection of supercritical CO2 and brine at reservoir conditions. The performance of such particles to stabilize CO2-foam has ramifications on current implementation of oil recovery and CO2 storage for reduced carbon footprint during injection of CO2 in mature oil fields. Quantitative analysis of oil recovery efficiency, pressure gradients, and rate of oil recovery were used to study displacement mechanisms and to evaluate the feasibility of using nanoparticles as CO2 foaming agents. Two main observations were made: 1) silica nanoparticles stabilize CO2-foam in the presence of oil and remain stable during oil displacement: the pressure gradient measured during tertiary co-injections with nanoparticles was between 3 and 5 times higher than without foaming agent. 2) nanoparticle-stabilized CO2-foam increase oil recovery: the incremental oil recovery after waterflooding during tertiary co-injection increased by a factor of two with nanoparticles relative to co-injection with brine.