Construction of a High-Temperature and High-Salinity Resistant Hydrogel for Profile Control in Underground Reservoirs

Hydrogels have been widely applied as plugging agents for profile control in oilfields due to their favorable swelling behavior, deformability, and pore-throat plugging ability. However, many hydrogels suffer from poor plugging performance due to hydrolysis and hardening under high-temperature and high-salinity conditions. In this study, a novel hydrogel designated as ADSI (A: acrylamide; D: divinylbenzene; S: vinyltrimethoxysilane; I: 1-vinylimidazole) is developed for high-temperature and high-salinity conditions. In this gel, polyacrylamide (PAAm) acts as the backbone, incorporating divinylbenzene (DVB), vinyltrimethoxysilane (VTMS), and 1-vinylimidazole (VIM). Characterization results indicate that this hydrogel shows good high-temperature and high-salinity stability, mechanical properties, and plugging ability in high-permeability layers. After aging in 20 × 104 ppm brine at 120 °C for 14 days, this gel still maintains good structural stability, with a swelling ratio of 706.98% and a relatively uniform particle size distribution. Thermal Gravimetric Analysis (TGA) shows that the onset decomposition temperature is 236.8 °C, higher than that of pure PAAm gel. Mechanical tests show that the fracture stress is 24 kPa with a maximum strain of 315%, enabling migration and plugging in porous media. Core flooding experiments demonstrate that the AD6S7I10 formulation (60 μL DVB, 70 μL VTMS, and 100 μL VIM) achieves a plugging efficiency of 92.41%. This hydrogel may serve as a candidate for profile control in complex reservoirs.