Degradable PAM hydrogel mediated by hydroxy acids for temporary plugging

In this study, the degradation time of gel plugs was regulated by introducing hydroxy acids to adjust the crosslink density, effectively addressing the challenge of controllable degradation time in existing gel plugs. The degradation time of the self-degradable gel plug (SDGP) was extended from 53 h without acid to 235 h with the addition of tartaric acid. Notably, the introduction of hydroxy acids not only regulated the degradation time of the SDGP but also enhanced its properties. The breakthrough pressure of the SDGP without acid was 0.53 MPa, while that of the SDGP with citric acid was 0.74 MPa. Additionally, self-degradation of the SDGP could be achieved after maintaining high strength for a period, ultimately degrading to a liquid with a viscosity of less than 200 mPa⋅s. The introduction of hydroxy acids increased the crosslinking density between polymer chains and reduced the internal free water content, thereby slowing the hydrolysis of ester groups to achieve controlled degradation of the SDGP. Furthermore, when the crosslinker poly(ethylene glycol) diacrylate was hydrolyzed, the hydroxy acids acted as a crosslinker to re-crosslink the polymer chains, with both the hydroxyl and carboxyl groups in the hydroxy acids participating simultaneously. This study provides a novel approach to adjusting crosslink density to regulate the degradation time of temporary plugging polymer gels, which avoids subsequent gel-breaking operations, reduces costs, and simplifies the operation process.