Development and Application of a Long-Lasting Composite Gel Plugging Agent with Temperature-Gradient Regulation

After multiple cycles of steam stimulation in heavy oil reservoirs, exacerbated reservoir heterogeneity leads to severe steam channeling, rapid water cut increase, and significant residual oil accumulation in interwell zones. To address these challenges, a high-strength, long-lasting plugging agent is urgently needed to effectively seal steam channeling pathways. Based on the formulation consists of “acrylamide copolymer + phenolic resin crosslinker”, this study developed a temperature-gradient-regulated composite gel plugging agent by incorporating an organic boron retarder and nano-silica. The rheological properties, migration capacity, and thermal stability of gel were evaluated through rheometry and core flooding experiments. Field trials were conducted in the Shengli Oilfield. Through experimental optimization, the optimal formulation of the gel plugging agent consists of “0.5% polymer + 0.5% phenolic resin + 0.3% retarder + 4% nano-silica.” At 60−80 ℃, the gel initiated crosslinking within 3–7 days, forming a weak gel structure. In 18-m core experiments, this gel achieved a migration distance twice that of conventional gels, demonstrating potential for deep reservoir penetration. At 160 ℃, it achieved secondary crosslinking within 2 h, developing a high-strength gel with a plugging strength of 7.2 MPa/m. After 30 days of aging at 160 ℃, the gel exhibited no syneresism while maintaining a plugging strength of 5.1 MPa/m, demonstrating excellent long-term stability. The gel plugging agent has been applied in over 50 wells in potential blocks such as Gudao and Binnan in the Shengli Oilfield, increasing the cycle oil-steam ratio by 0.14. This technology provided a reliable solution for cost-effective development and sustained production of heavy oil reservoirs.