The characterization and enhanced oil recovery mechanisms of a nanosized polymeric cross-linked gel are presented herein.A negatively charged nanogel was synthesized using a typical free radical suspension polymerization process by employing 2-acrylamido 2-methyl propane sulfonic acid monomer.The synthesized nanogel showed a narrow size distribution with one peak pointing to a predominant homogeneous droplet size.The charged nanogels were also able to adsorb at the oil-water interfaces to reduce interfacial tension and stabilize oil-in-water emulsions,which ultimately improved the recovered oil from hydrocarbon reservoirs.In addition,a fixed concentration of negatively charged surfactant (sodium dodecyl sulfate or SDS) was combined with different concentrations of the nanogel.The effect of the nanogels combined with surfactant on sandstone core plugs was examined by running a series of core flooding experiments using multiple flow patterns.The results show that combining nanogel and SDS was able to reduce the interfacial tension to a value of 6 Nm/m.The core flooding experiments suggest the ability of the nanogel,both alone and combined with SDS,to improve the oil recovery by a factor of 15％ after initial seawater flooding.