Nanofluids, which are dispersed nanoparticles (NPs) in aqueous or organic fluids, are effective in enhanced oil recovery. In this paper, different hydrophobic and hydrophilic silica NPs were dispersed in water to prepare nanofluids with the help of surfactants (CTAB, AOT, and TX-100). The contact angle of the model oil on the solid surface increased obviously when using the oil drop on a quartz plate immersed in nanofluids. Core flooding experiments showed that nanofluids displaced more oil from the core than the surfactant solution without NPs. Finally, we investigated the nanofluid effect mechanism on the separation of model oil from the solid surface by an adhesion work evaluation and the force-distance curve measurement with an atomic force microscope. We found that hydrophobic NPs were more easily adsorbed on the solid surface than hydrophilic NPs. Hydrophilic NPs were more easily adsorbed on the model oil surface than hydrophobic NPs. These results may provide a better understanding of the complex phenomena involved in the enhanced spreading of nanofluids on solid surfaces.