Abstract
In this study, electronegative silica nanofluid and electropositive alumina nanofluid were prepared to enhance oil recovery of ultra-low permeability cores. Transmission electron microscopy and dynamic light scattering were employed to characterize their morphology and size. Nanofluids with different concentrations, ranging from 0.001wt% to 0.2 wt%, were used for spontaneous imbibition tests of sandstone cores to evaluate the performance of these nanofluids for EOR. The wettability alteration experiment and zeta potential measurements were employed to investigate the mechanism of nanofluids for EOR. As the concentration of alumina nanofluid increases, the adsorption of alumina nanoparticles could cause pore blocking. On the contrary, electronegative silica nanofluid could improve displacement efficiency and oil recovery as the increase of concentration of silica nanofluid. Electronegative silica nanofluid has great potential for EOR in ultra-low permeability reservoir.
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