3rd TAGRA

The unique physicochemical properties of hybrid hydrogels create broad opportunities for their application in oil and gas engineering. In particular, these systems can be effectively utilized for formation water shut-off, selective plugging of high-permeability channels, profile control, and reservoir permeability restoration. The present study focuses on the swelling mechanisms of a xanthan/polyacrylamide-based hydrogel in various aqueous mediums, including buffer and saline solutions. The well-defined three-dimensional network was obtained in alkaline medium at a xanthan:PAAm mass ratio of 1:3 when the crosslinker concentration was in the range of 0.15–0.4 wt%. The swelling of the hydrogel increased with temperature, shows enhanced polymer chain mobility and accelerated water diffusion, and was systematically investigated in DW and physiological saline at 293-343 K. At all temperatures, the swelling degree increased with time, indicating a diffusion-controlled water uptake process followed by network relaxation. This behavior suggests that higher temperatures promote polymer chain mobility, reduce hydrogen bonding, and enhance solvent diffusion into the hydrogel network. In 0.9% NaCl solution also exhibited a clear temperature dependence; however, the overall swelling degree was lower than that observed in DW. The reduced swelling in saline medium can be attributed to the ionic strength effect, where Na⁺ ions partially screen the negatively charged functional groups of xanthan, thereby decreasing electrostatic repulsion and osmotic pressure within the network. The equilibrium swelling of the Xanthan/PAA hydrogel exhibited a temperature dependence in both DW and NaCl solution. In DW, the swelling capacity increased with temperature, indicating an endothermic and entropy-driven process due to enhanced chain mobility of the polymer network. The slight deviation observed at intermediate temperatures may be attributed to structural rearrangements and hydrogen-bond reorganization within the hydrogel matrix. In NaCl medium demonstrated more complex, non-monotonic behavior due to the competition between thermo activation and ionic screening effects.