Modulation of syneresis rate and gel strength of PAM-PEI gels by nanosheets and their mechanisms

To address the issue of traditional gels being prone to dewatering and failure under reservoir conditions, this study prepared a new type of magnetic smart gel by 'chelating' PEI@Fe 3 O 4 @PEI nanosheets within the PAM-PEI gel network. The nanosheets possess a 'sandwich' structure formed through self-assembly driven by electrostatic forces, with a density of 2.719 g/cm 3 . Under 90 °C and with a NaCl concentration of 25 g/L, the control PAM-PEI gel had a syneresis rate of 5.96 % and a gel strength of 17.13 Pa·s. In comparison, the magnetic smart gel had a syneresis rate of 0 % and a gel strength of 27.38 Pa·s, indicating that the magnetic smart gel outperformed the control significantly. Possible mechanisms by which nanosheets enhance the performance of magnetic smart gels include: enhancing the hydrophilicity of the molecular chains, inhibiting the breakage of C-N bonds in the polymer chains, increasing the gel's resistance to water loss at high temperatures, and hindering the pyrolysis of PAM groups. Lastly, the work explores the advantages of magnetic smart gels in effective plugging, rapid unplugging post-lifespan, and simplified produced water treatment through its controlled operational capabilities. To implement these applications effectively, field devices need to be equipped with innovative designs.