In this paper, we describe the synthesis, characterization and evaluation of nanocomposite preformed particle gels (PPGs) for use as conformance control agents in high-temperature and high-salinity oil reservoirs. The chemical stability of conventional acrylamide (AM)-homopolymer-based PPGs was improved by incorporating an optimized ratio of new functional groups into their structure to withstand harsh reservoir conditions. The modified PPGs were synthesized via free radical crosslinking polymerization at room temperature using AM, vinylpyrrolidone (VP) and 2-acrylamido-2-methylpropane sulfonic sodium salt (AMPSNa) monomers and an N,N-methylenebis (acrylamide) (MBA) crosslinker. The mechanical properties of the PPGs were enhanced by adding a dispersion of modified bentonite (MB) to the formulation. The chemical and mechanical stabilities of the synthesized PPGs were evaluated at a high temperature (130 °C) and under high-salinity conditions using production water (with a TDS of 83 942.63 p.p.m.) and connate water (with a TDS of 254 873.09 p.p.m.), both of which were collected from an oil reservoir. The experimental results showed that PPGs prepared with 30 wt.% of a 1:1:1 molar mass ratio of AM, VP and AMPS monomers with 0.5 wt.% MBA and 2 wt.% MB exhibited the highest stability of the investigated PPGs under oil reservoir conditions.