Nanoparticles for Inhibition of Asphaltenes Deposition during CO2 Flooding

The deposition of asphaltenes in porous media is one of the most difficult problems during CO2 flooding. In this paper, the adsorption of asphaltenes onto Al2O3 nanoparticles was studied through two methods: (i) by adding a certain mass of nanoparticles in a fixed volume of solution with different initial concentrations of asphaltenes and (ii) by exposing-a certain amount of asphaltenes in a fixed volume of solution to different nanoparticles additions. Then, the impact of Al2O3 nanoparticles on the asphaltene precipitation was investigated using the IFT behavior of the oil-CO2 system. Coreflood tests were conducted to study the potential Of nanoparticles for inhibition of asphaltenes damage during CO2 flooding, and the effect of injection parameters of nairofluid. It is found that the solid-liquid equilibrium (SLE) can well describe the, isotherms of asphaltene adsorption. The trend of the IFT-pressure curve is affected by asphaltene accumulation at the oil-CO2 interface. The slopes in the high pressure region can be used to examine the intensity of asphaltene precipitation. As the addition of nanoparticles increases, the IFT slope in the high pressure range decreases. This is because the asphaltenes are absorbed at the surface of nanoparticles. As a result, the nanoparticles prevent asphaltene precipitation from accumulating at the CO2-oil interface, hence causing asphaltene to remain within the bulk of oil. The higher the mass fraction of Al2O3 nanoparticles is, the lower the intensity of the asphaltene precipitation would be. The coreflood results show that the injection of Al2O3 nanofluid can lessen the oil permeability reduction because the nanoparticles can inhibit the deposition of asphaltenes onto the sand surfaces in the porous media. The 0.5 wt % nanoparticles and the 0.1 nanofluid/CO2 slug volume ratio are considered as the optimum for inhibiting asphaltenes damage during CO2 flooding. Continuous CO2 and nanofluid injection could be more effective compared with the cyclic injection pattern.