High demand in the reduction of viscosity of heavy oil from reservoir sandstone has been a great interest with the applications of electromagnetic (EM) assisted for the enhanced oil recovery. Therefore, the conversion of EM waves properties into the reservoir region must be taken into consideration and the interaction between the reservoir fluids and the solid phases. In this study, the rheological and adsorption effect of Fe3O4, ZnO, Al2O3, SiO2, and CuO at high temperature and pressure on reservoir sandstone have been simulated using Biovia material studio and experimentally investigated with the effect of electromagnetic waves. The measurement of the viscosity are at a different shear rate for dielectric and magnetic nanofluids. The viscosity of the crude oil varies over a range of shear rates (100�2000 s�1) and temperatures (25�120 °C), the crude oil exhibited extremely high viscosity at a low shear rate and low temperature, and gradually drifts to lower viscosity at the reservoir conditions (2000 s�1 - 119 °C). It was revealed from the result that Fe3O4 Nanofluid exhibits better performance compares to ZnO, and Al2O3 at a high shear rate (2000, 1500, and 1000 s�1) at reservoir condition. Nanofluid shows Newtonian behavior with an increase in shear rate and the viscosity of the oil decrease with an increase in temperature. As the dispersion of the particles increases, the interactions between the components of sandstone crude Oil and nanoparticles also increased, that favors viscosity reduction which in turn increase the fluid mobility. © 2021 Elsevier B.V.