Preparation And Properties Of Crosslinked Polyacrylamide Microspheres

Polyacrylamide gels are the main polymeric additives in water plugging and profile control process.But the heterogeneity of each oilfield reservoir is becoming wider and wider,the traditional polyacrylamide gel has been unable to meet the requirements of oilfield development,with the deepening of oil exploitation in China.Researching a proper plugging-agent to meet the requirement of depth profile control and water plugging is particularly urgent.In this paper,by means of acrylamide and 2-acrylamido-2-methyl propane sulfonic acid(AMPS)as monomers,compounding labile crosslinker with stable crosslinker,acrylamide composite microspheres with different particles size were synthesized,by inverse miniemulsion and inverse suspension polymerization.And the delayedswelling characteristic,control methods and hydrogel microspheres toughening methods were explored.Above all,three kinds of quaternary ammonium salt crosslinking agent were prepared,respectively for N,N'-ethylene glycol diacetate bis[(3-acrylamido)propyl dimethylammonium bromide](BEBC),(N,N'-butyl bis[(2-acryloyloxy)ethyl dimethylammonium bromide](BQAEC),(N,N'-butyl bis[(3-acrylamido)propyl dimethylammonium bromide](QAAC),by quaternization reaction of tertiary amine and halides.In order to compare the hydrolysis rate of crosslinkers,the change of swelling degree with time was determined.The results showed that the hydrolysis rate order: BEBC > BQAEC > TEGDA >> QAAC ? Bis.Submicron polyacrylamide crosslinked microspheres PAMSMM was prepared by inverse miniemulsion polymerization,with BQAEC/Bis as crosslinker.The particle size of the microspheres was 300 nm~ 500 nm.The swelling kinetics of microspheres were characterized by viscosity,transmittance and swelling degree.PAMSMM with BQAEC as crosslinker had obvious delay-swelling characteristics,and the swelling rate of the microspheres was determined by the dosage of BQAEC,the dosage of Bis,pH and temperature.The hydrolysis rate of BQAEC decreased with the decrease of pH,and the hydrolysis rate was the slowest under weak acid condition.By means of BQAEC/QAAC as crosslinking agent and introducing polyvinyl alcohol(PVA),PAM/PVA composite crosslinked SIPN microspheres were prepared by inverse suspension polymerization.The average particles size of microspheres is between 10 ?m and 150 ?m.The size of microspheres can be adjusted by the compound dispersing agent ratio,the dosage of emulsifier and the dosage of PVA.The crosslinked microspheres showed delay-swelling characteristic.The swelling rate of microspheres can be adjusted by the dosage of BQAEC,and the equilibrium swelling degree can be adjusted by the dosage of QAAC and PVA.Semi-interpenetrating network can improve the mechanical properties of the microspheres.Young's modulus increased 3 times,the fracture strain was 0.88 and fracture strength for 400 kPa.The branching gels were preapareed by copolymerization of AM and AMPS,by N-(3-dimethylaminopropyl)acrylamide as branching agent,and potassium persulfate(KPS)as initiator.The swelling degree of the branching gels up to 1000 g/g.The branching gels has good flexibility.After many times cyclic compressing test,gels were not broken.And to improve the mechanical properties of gels,the semi-interpenetrating network technology was introduced.