How do metal oxide nanoparticles influence on interfacial tension of asphaltic oil-Supercritical CO2 systems?

Often, supercritical CO2 is injected into oil reservoirs as a miscible gas. CO2 injection might force asphaltene particles to precipitate. To reduce asphaltene precipitation, it might be a good solution to use asphaltene adsorbents like metal oxide nanoparticles. Diffusion of supercritical CO2, containing suspended nanoparticles, into oil slugs would decrease asphaltene precipitation as a result of nanoparticles high adsorption capacity. In this research, IFT values between the supercritical CO2 and different crude oil types, which are saturated with NiO, Co3O4, and Fe3O4 nanoparticles, have been measured. Furthermore, effects of different crude oil properties such as API gravity, asphaltene content, and sulfur content on the nanoparticles performance are also investigated. Accordingly, nanoparticles performances order is NiO > Co3O4 > Fe3O4. In addition, it is found that oil properties effects on IFT reduction are not synergistic; so, the overall effect must be evaluated quantitatively to understand IFT reduction of the system.