In Situ Polymer Gel for High‐Salinity Water Control in Sandstone: Formation, Rheology, and Thermal Stability

Abstract Gels generated in situ within porous media, despite serving as non‐selective blockers, constitute valuable options for managing water in oil‐producing wells while minimizing the risk of formation damage. Accordingly, this study involved the preparation of gel formulations employing an ionic terpolymer and cross‐linkers such as hexamethylenetetramine and resorcinol. The gels formed in the presence of brine with salinity of 250,000 ppm were classified as rigid according to the Sydansk scale. They were identified as chemical gels through rheological analysis. Furthermore, these gels demonstrated thermal stability at 160 °C, over up to four months. The in situ‐formed gels within porous media exhibited fluid control efficiencies exceeding 96% in both homogeneous and fractured rocks, as exemplified by sandstone cores, following secondary oil recovery processes. This was achieved using brine with salinity of 250,000 ppm (comprising 150,000 ppm NaCl and 100,000 ppm CaCl 2 ) as the displacement fluid at 130 °C.