Preparation And Properties Of Polymer Gel Particles Based On Underground In Situ Gelation

Polymer gel particles have been widely used in oilfields for water plugging,and profile control due to their simple synthesis process,convenient construction,good water-swelling performance,and good viscoelasticity.However,the current polymer gel particle dispersion systems are hard to form gel and their viscosities are rather low after injecting underground.Therefore,acrylamide（AM）,temperature-resistant monomer 2-acrylamide-2-methylpropanesulfonic acid（AMPS）and organic metal cross-linking agents were used to synthesize series of target polymer gel particles through solution copolymerization initiated by potassium persulfate-sodium bisulfite redox system.The effects of initiator dosage,main agent dosage,crosslinking agent dosage and pH on solution copolymerization were investigated in detail,and the synthesis conditions of polymer gel particles were determined accordingly.The synthesized polymer gel particles were characterized by infrared spectroscopy,carbon nuclear magnetic resonance spectroscopy,scanning electron microscopy and energy dispersive spectroscopy measurements.The influencing factors of water swelling ratio were explored,and the effects of crosslinking agent dosage,main agent ratio,temperature and polymer concentration on the viscosity of polymer gel particle dispersion system were also studied.The influencing factors of its plugging performance were explored through core plugging experiments.Polymer gel particles were successfully synthesized by using 23 wt%main agent,0～2wt%cross-linking agent,and 0.0125 wt%initiator under low temperature（<15℃）and pH=7.When the content of cross-linking agent was 0.5 wt%and the ratio of main agent was AM/AMPS=80/20,the water-swelling ratio of polymer gel particles reached the largest,up to820 times.The higher the proportion of AMPS in the monomer,the higher the concentration of the polymer gel particle dispersion system and higher aging temperature,the better the viscosity enhancement of the dispersion system.Specifically,when the ratio of AM and AMPS was 80:20,and the amount of crosslinking agent was 0.5 wt%,the viscosity was the highest（2400 mPa·s）.When the aging temperature was 90℃,the viscosity-increasing performance of the system was the best,up to 360 mPa·s,which was about 14 times of the viscosity at 50℃.The core flooding experiment found that when the injection volume was1.0 PV,the system concentration was 3000 mg/L,and the core permeability was 5000×10^-3μm²,the polymer gel particle dispersion system had the best plugging performance and the highest water plugging rate was up to 99.4%.