Nanotechnology could be used to develop new methods for improved/enhanced oil recovery (IOR/EOR). In the present research work we have applied nanoparticles of silica (SiO2) which offers several benefits; inorganic, easily produced, one of the most abundant materials, non-toxic, existing as several minerals and produced synthetically. In addition, the surface properties of silica nanoparticles are easily treated. Another important thing is that the size of the nanoparticles is much smaller than the common reservoir pore throat, giving them the ability to propagate in reservoir rock. Laboratory experiments were prepared to unlock the potential of nanoparticles for enhanced oil recovery. Various types and sizes of nanoparticles, crude oil, nanofluids dispersed in various types of synthetic sea water, glass micromodel and core samples were characterized. Relevant reservoir aspects and parameters such as nanoparticle aspects (size, concentration, and type), the presence of a stabilizer, permeability variation, initial rock wettability, temperature, salinity, salt ionic composition, the injection rate and its strategy are discussed. Fluid-fluid and fluid-rock interactions are also investigated to reveal a possible displacement mechanism using nanoparticles such as interfacial tension, pH, surface conductivity and wettability alterations. We select inorganic nanoparticles that are long time stable at a high temperature and in a high-salinity water/oil environment, are easily prepared in a large-scale production with a relatively low cost and are environmentally friendly. When nanoparticles are exposed to fluid and injected into a reservoir the interaction of nanoparticles with their surroundings determines their transport behavior and functionality. On nanoscale, the interfacial properties between nanoparticles and water/oil/rock were characterized by a particle analyzer and in-situ scanning electron microscope. The results link the nanoparticle interaction and nanofluid rheology to the applied nanoparticle type, size, concentration, and surface properties. Transportability is a pre-requisite for nanoparticles to be useful in reservoir application, and particle retention was observed and measured. The overall investigations from this research show that hydrophilic nanoparticles have great potential for EOR and offer benefits in challenging reservoir conditions such as high salinity, high temperature, different initial rock wettability, and low permeability. The type and size of nanoparticles affects nano-EOR performance. It was also observed that Nano-EOR performance could be maximized by optimizing the nanofluid concentration and adding a stabilizer. By evaluating the contact angle, pH, surface conductivity and interfacial tension as the proposed displacement mechanisms in Nano-EOR, it was observed that wettability alteration played an important role.