| Abstrakt: |
Nanoparticles (NPs) have been applied in enhanced oil recovery (EOR) successfully over the last couple of decades, due to their unique property inherited by the small size (most of the studies focused on sizes smaller than 50 nm) and abundant surface functional groups. The important mechanism of EOR using a NP-based nanofluid is the change of interfacial properties. However, the effect of the nanoparticle size on the same type of oil recovery has not been systematically studied, especially the larger size. Therefore, in this research, SiO2NPs of different sizes, namely, ∼60, ∼100, ∼200, and ∼300 nm, were synthesized using the Stőber method and the properties of the NP-based nanofluids were investigated, including interfacial tension (IFT), contact angle, viscosity, capillary pressure, and the ability to extract oil. The experimental results showed that as the SiO2NP size decreased, there was a little increase in the IFT, oil contact angle, viscosity, and capillary pressure. With a NP concentration of 0.3 wt % in 3 wt % NaCl brine, the ∼60 nm SiO2NP-based nanofluid was the most efficient oil-displacing agent to recover oil from the medium-permeability core sample of Daqing Oilfield. Therefore, according to the discussion of the selective preference for SiO2NP sizes, the developed nanofluid is a promising new material in medium-permeability reservoirs for enhanced oil recovery. |
