Preparation of Ultra‐Salt‐Tolerant OEMA Hydrophobic Modified Viscoelastic Profile Control Gel and Study of Its Salt Thickening Characteristics and Plugging Performance

ABSTRACT To address the challenges of strong matrix heterogeneity, a limited flooding sweep range, and low oil displacement efficiency in high‐salinity and high‐water‐cut tight reservoirs, an amphiphilic monomer (OEMA) was introduced via aqueous dispersion polymerization to synthesize a profile control agent (SMAA‐n) with excellent water dispersibility, salt‐thickening properties, and viscoelasticity. The storage modulus of SMAA‐n exceeds the loss modulus, indicating that the profile control agent is an elastic fluid. In a salt ion environment (K + , Na + , Ca 2+ , and Mg 2+ ), viscosity increases with OEMA content, producing salt‐thickening characteristics alongside good thixotropic recovery. The hydrophobic association between the octadecyl long chains enable SMAA‐n to form a dynamic network structure capable of inversion, achieving plugging via salt thickening in matrix pores, particle adaptive pore matching, and shear deformation. Introducing OEMA into the synthetic profile control agent enhances the core plugging rate, with the average value exceeding 85.0%. The final oil recovery rate of SMAA‐5% is 47.32%, considerably higher than that of unmodified SMA (36.52%). The salt thickening and strong plugging of SMAA‐n provide a new approach for profile control and flooding to enhance oil recovery in high‐salinity, high‐water‐cut heterogeneous reservoirs.