盐、温度和pH值对纳米SiO_(2)/HPAM分散体系稳定性和流变性的影响

Effects of Salt Environments,Temperatures and pH Values on the Stability and Rheology of Nano SiO_(2)/HPAM Dispersed Systems

利用浊度法、纳米粒度及Zeta电位分析仪、流变仪研究了盐环境、温度和pH值对纳米SiO_(2)/部分水解聚丙烯酰胺(HPAM)分散体系稳定性及流变性的影响。结果表明,金属阳离子(特别是二价阳离子)使SiO_(2)/HPAM聚集体粒径减小,分散体系的Zeta电位绝对值降低,导致稳定性下降。对比HPAM溶液,加入纳米SiO_(2)后,SiO_(2)/HPAM去离子水分散体系的黏度和储能模量降低,其盐水(地层水)分散体系的黏度和储能模量升高。随着SiO_(2)加入量增加,SiO_(2)/HPAM氯化钠盐水分散体系的流变性先升高后降低,其地层水分散体系的流变性持续增加。对于SiO_(2)/HPAM地层水分散体系,当SiO_(2)质量分数为0.5%时,温度升高则分散体系黏弹性降低;SiO_(2)质量分数为1.5%时,温度升高则分散体系黏弹性急剧增加。当体系的pH值变小时,则其Zeta电位绝对值和黏度降低,SiO_(2)/HPAM去离子水分散体系稳定性变差,而地层水分散体系稳定性改善。

The effects of salt environments,temperatures and pH values on the stability and rheology of nano-SiO_(2)/partially hydrolyzed polyacrylamide dispersed systems were studied by the turbidity method together with Zetasizer and rheometer.The experimental results suggest that both the absolute value of zeta potential and SiO_(2)/HPAM aggregate size decrease with the presence of metal cations,especially divalent metal cations,resulting in the deterioration of the stability of dispersed systems.With the addition of nano-SiO_(2),the viscosity and storage modulus of HPAM in deionized water environment decrease.However,the viscosity and storage modulus of HPAM in salt environments are strengthened.With the increase of nano-SiO_(2) concentration,the rheology of dispersed systems increases first and then decreases in the NaCl solution environment,but the rheology increases continuously in formation water environment.For SiO_(2)/HPAM dispersion systems in formation water environment,the viscoelasticity of dispersed systems decreases with the increase of temperatures when the nano-SiO_(2) mass fraction is 0.5%,while an opposite phenomenon has been observed when the nano-SiO_(2) mass fraction is 1.5%.With the decrease of pH values,both the zeta potential and viscosity decrease,and the stability of dispersed systems in deionized water environment becomes worse,while the stability in formation water environment is improved.