Abstract
<title>Abstract</title> <p>Gel treatment represents a significant technical method for addressing the issue of excessive water production in oilfields. The stability and plugging properties of the gel are pivotal factors in determining the effectiveness of the treatment. In this study, two acrylamide/2-acrylamide-2-methylpropanesulfonic acid (AM/AMPS) copolymers with different AMPS content were crosslinked with hydroquinone (HQ) and hexamethylenetetramine (HMTA) to prepare gels adapted for high-temperature and high-salinity reservoirs at 110 °C in brine with a salinity of 250 000 mg/L. The comparison of the performance of the two gels showed that with the same polymer and crosslinker concentrations in the gel, the gelation time of the AM/AMPS copolymer with 60% AMPS content (CP60) was longer than that of the copolymer with 30% AMPS content (CP30). The gel strength was also lower but the thermal stability was better. A water-flooding experiment was conducted to compare the plugging capabilities of the two gels in a porous medium. The results indicated that, under identical conditions, the plugging pressure difference of the CP30 gel in the porous medium was greater than that of the CP60 gel. However, when the cross-linking agent concentration was 0.4%, there was a significant difference in gel strength between the two gels, whilst their residual resistivity coefficients in the porous medium were relatively similar. Rheological analysis indicated that this phenomenon was attributable to differences in the rheological properties of the two gels. As gel strength increased, the CP30 gel became more brittle, whilst the CP60 gel became more ductile. Analysis of the gels’ rheological behavior elucidated the mechanism by which gel rheology influences plugging performance. Finally, Fourier transform infrared spectroscopy was employed to elucidate the stabilization mechanisms of the two gels. Based on the insights gained from this study into gel plugging and stabilization mechanisms, methods can be developed to modulate gel properties, thereby providing better guidance for the application of gels in water shutoff in oilfields.</p>