Gel treatment is one of the most promising technologies to improve conformance control in heterogeneous reservoirs. In this paper, new enhanced preformed particle gels (PPGs) are introduced for conformance control in highâtemperature and highâsalinity oil reservoirs. The thermoâchemical stability of this product is due to the incorporation of a new monomer, N,Nâdimethyl acrylamide (DA), to the structure of the last wellâknown nanoâcomposite PPGs. Four species, N,Nâdimethyl acrylamide, 2âacrylamidoâ2âmethylpropane sulphonic sodium salt (AMPSNa), acrylamide (AM), and Nâvinylpyrrolidone (NVP) monomers, were used to synthesize these PPGs via free radical crossâlinking polymerization at room temperature using N,Nâmethylenebis (acrylamide) as a crossâlinker. The mechanical properties of these new classes of PPGs were enhanced by adding the nanoâclay montmorillonite Na+. A temperature stability agent was also used to make these special PPGs compatible with high temperature and salinity reservoir conditions. A systematic study on PPGs preparation was conducted to improve PPGs stability for harsh reservoir conditions that exist in Persian Gulf oil reservoirs (a temperature of 145â°C and a water total dissolved solid of 225â000âmg/L). PPGs prepared with 0.30âg/g (30âwt%) of a 2:1:1:2 molar mass ratio of AM, DA, NVP, and AMPSNa could be completely stable for the mentioned conditions. Rheological behaviours of these PPGs were investigated and a mathematical model for prediction of storage modulus up to onset of elastic to viscous phase was presented. The results of this study reveal useful insights about the selection of appropriate material for successful conformance control in the heterogeneous reservoirs.