Cost-effective phenolic resin gels under high temperature and high salinity conditions: gelation performance, oilfield-ready formulations, and syneresis mechanisms

Abstract

This study explored the gelation characteristics of the partially hydrolyzed polyacrylamide (HPAM)/phenolic resin gel system in Bonan oilfield’s high temperature (130 °C) and high salinity (20,348 mg/L, 41,529 mg/L) conditions. Polymer (0.4–1.0 wt%) and crosslinker (0.1–0.4 wt%) dosages were varied, while thiourea and nano-SiO₂ loadings were both fixed at 0.3 wt%. At 20,348 mg/L salinity, gelation took 3–46 h, forming stable medium to strong gels. At 41,529 mg/L, gelation shortened to 3–17 h with medium to strong gels formed, but some gels dehydrated over time, especially for gels with low crosslinker content. Overall, higher salinity sped up gelation, increased short-term strength but decreased long-term stability. Polymer dosage ≥ 0.8 wt% and crosslinker dosage ≥ 0.3 wt% ensured stability under both salinities. The optimized formulation, with a yield stress of 60 Pa and breakthrough pressure gradient over 190 MPa/m under two salinity conditions, shows potential for formation plugging. Cryo-SEM, XPS, and FTIR analyses revealed three synergistic mechanisms governing the syneresis of high-salinity gels. Strategic optimization of crosslinker concentration can enhance gel stability. These findings can guide gel applications in profile control and water shutoff in Bonan oilfield and similar reservoirs.

Graphical Abstract

It represents the creep compliance, yield stress, and the pressure curves in the flooding experiment of the optimized formulation after aging at 130 °C aged for 3 days: a 20,348 mg/L and b 41,529 mg/L.