Advancements in nanoparticle-based stabilization of CO₂ Foam: Current trends, challenges, and future prospects

Modern technology must meet the urgent need for net-zero global carbon emissions to mitigate the deleterious effects of fossil fuel consumption. CO2 utilization in fields such as oil extraction not only prevents global warming, but also has universal benefits. CO2 flooding is a well-established and promising technology for enhancing residual oil recovery. Enhanced oil recovery (EOR) from fractured reservoirs is difficult because the injected fluids cannot displace crude oil from the matrix. This may be attributed to the (i) lighter weight and lower viscosity of CO2 than those of the crude oil in the reservoir and (ii) highly permeable layers in the res-ervoirs, which provide a "path of least resistance" for CO2 flow. The injection of large amounts of foam into the matrix can be achieved using a strong and stable foam, which generates high pressure in the fractures by blocking the highly permeable layers and directing the CO2 towards less permeable zones. Extensive efforts have been devoted to improving the long-term stability of CO2 foams. Such approaches include the use of surfactants (cationic, anionic, non-ionic, and zwitterionic), viscoelastic surfactants (VES), polymers, and nanoparticles (NPs). This article provides a brief overview of the basic principles underlying CO2 foam stabilization, selection of surfactants, choice of NPs, the role of surface functionalization of the particles, and various factors affecting CO2 foam stabilization, reported during 2016-2023. Furthermore, this review highlights the need for experi-mental protocols to investigate NP-stabilized CO2 foams.