Treatment with preformed particle gels (PPGs) is one of the most promising solutions to improve the Conformance Control of mature water-flooded oil reservoirs. It is very important to be able to evaluate and predict the performance of PPGs in porous material. In this paper, we first present a new class of advanced nanosized PPGs designed for harsh reservoirs (high salinity and temperature) and then present experimental laboratory results investigating the viscosity of nanosized PPGs (NS-PPGs) during injection and flow in porous media. The functionality of the NS-PPG rheological behavior was fully evaluated under different fracture flow conditions. The effects of three variables, including tube internal radius, injection rate, and NS-PPG size, on the viscosity of the NS-PPGs were investigated. The results showed that NS-PPG viscosity mainly depends on the injection rate, tube inner radius, and PPG size. The rheological properties of these NS-PPGs were examined, and a mathematical model was developed to predict the storage modulus until the transition from the elastic to viscous phase. The findings from this study provide valuable insights into the selection of suitable materials for effective conformance control in heterogeneous reservoirs.