Nanotechnology has potential applications in different industrial areas, and it is often considered as one of the most promising technological breakthroughs of the last few decades. Nanoparticles are extensively used in the form of water based nanofluids with or without other chemicals to enhance oil recovery. However, displacing oil-based nanofluids by water under oil-wet conditions has been inconclusive due to an unstable oil-based nanoparticle dispersion. The aim of this dissertation was to investigate the potential of utilizing oil based nanofluids for sweep efficiency and oil recovery under oil-wet conditions. Oil soluble silica nanoparticles with amphiphilic interface affinity were firstly synthesized and characterized. The primary evaluation was conducted by waterflooding of oil-based nanofluids in an oil-wet sandpack embedded in a CT scanner. Although sweep efficiency improvement was observed in the presence of oil-based nanofluids due to the in-situ emulsion formation at the water invading front, the presence of an oil-based nanofluid naturally in porous media does not have applications in the oil industry. This led to the question of where can oil-based nanofluids be used as an EOR agent? A possible answer was through solvent flooding of heavy oils. In this regard, solvent based nanofluid flooding followed by waterflooding was developed as a novel heavy oil recovery technique to improve recovery of a moderate viscous crude oil under oil-wet conditions. In addition to the oil viscosity reduction due to the presence of solvent, the presence of partially hydrophobic nanoparticles and a surfactant in the solvent based nanofluid was found to potentially generate in-situ emulsions with the chase water, stabilizing the chase water front in turn. It was demonstrated that appropriate delivery of solvent based nanofluid by water alternating solvent based nanofluid injection significantly improved sweep efficiency and oil recovery using less amount of solvent. Since thermal techniques are not applicable in non-water-wet heavy oil carbonates due to the reservoir heterogeneity, this novel solvent based nanofluid injection can be an alternative non-thermal oil recovery technique. It can be applied for heavy oil recovery from oil-wet carbonates such as those in the North Central Alberta or conventional oil-wet carbonate formations in the Middle East. This process can be further evaluated for different types of heavy oil, solvent, and nanoparticles to assess its technical applicability.