Stabilization of CO2 foam using by-product fly ash and recyclable iron oxide nanoparticles to improve carbon utilization in EOR processes
Fly ash nanoparticles (NPs), a by-product of coal combustion power plants, and recyclable iron oxide NPs are used to stabilize CO2 foam for use in enhanced oil recovery (EOR) processes as part of carbon capture, utilization and storage. The mean size of fly ash NPs is reduced to the nano-scale (40–80 nm) by a two stage grinding process. Iron oxide (IO) NPs are synthesized through Fe2+ and Fe3+ co-precipitation. The size and uniformity of the dispersion of NPs are characterized via dynamic light scattering and transmission electron microscopy. The stability and formability of NP-stabilized foam are investigated via a modified bulk foam test. The resulting improvement in oil recovery is investigated using flow experiments using a microfluidic device fabricated based on a two-dimensional representation of a Berea sandstone. The effects of the type of NP (fly ash and IO) on CO2 foam stability and the resulting incremental oil recovery are investigated and discussed. The results show that fly ash NPs with an Alpha-Olefin Sulfonate (AOS)–Lauramidopropyl betaine (LAPB) surfactant mixture provide excellent formability and stability (half-life 280 min) and resulted in over 90% recovery of the incremental oil after a waterflood in microfluidic experiments. Moreover, the material cost of fly ash NPs is significantly less than commonly used silica NPs. IO NP stabilized foam has an inferior foam stability and formability compared to fly ash stabilized foam; IO NPs can, however, be recycled using a magnetic field – the average recovery from the outflow of the microfluidic experiments was approximately 76%.