AbstractIn recent years, several experiments of various nanoparticles have been conducted for Improved/Enhanced Oil Recovery (IOR/EOR) by worldwide petroleum researchers. Most of them gave potential result to apply in full field case. In this paper, exp erimental study has been performed to evaluate oil recovery improvement using nanofluids injection onto several sandstone Berea cores. A hydrophilic silica nanoparticle with averages primary particle size 7 nm was used in this study. The synthetic brine 3 wt.% was made from sodium chloride (NaCl) and deionized water. This synthetic brine also used as diluents for nanoparticles.This study also investigated the effect of nanofluids concentration to permeability and porosity impairment. Hence, nanoparticles retention was extensively studied to explain that impairment includes analyses of pressure log-jamming, dynamic light scattering (DLS), Energy Dispersive X-ray Spectroscopy (EDS) and visualization under Scanning electron microscope (SEM). As a result, na nofluids concentration 0.01 wt.% was chosen in our experiment to minimize impairment and make it applicable in full field scale.Compare with brine flooding as secondary recovery, nanofluids flooding has up to 7.85% higher oil recovery onto Berea cores. T he nanofluids flooding also reduced residual oil saturation from 2 to 13% of pore volume at the core scale. Once brine flooding is performed after nanofluids, it only gives 0.53% additional oil recovery. As tertiary recovery, nanofluids flooding only give s up to 1.6% additional oil recovery following brine flooding. The essential result from our experiments showed that nanofluids flooding have more potential in improving oil recovery as secondary recovery rather than tertiary recovery.