稠油组分油水界面zeta电势及其影响因素研究

测定了辽河油田杜 84稠油化学官能团四组分 (酸性分、碱性分、两性分、中性分 )与极性四组分 (饱和分、芳香分、胶质和沥青质 )的zeta(ζ)电势 ,考察了水相pH值、盐度等因素对 ζ电势的影响。结果表明 ,官能团各组分间 ζ电势绝对值的差别较明显 ,其中酸性分最高 ,两性分最低、碱性分和中性分居中。酸性分在 pH =11时 ζ电势绝对值达到最高 ,其他组分的 ζ电势在 pH =12时达到最高。极性四组分 ζ电势绝对值差别不大 ,各组分 ζ电势绝对值都随着pH值升高而升高。在盐度为 1g/L左右时 ,各组分的 ζ电势绝对值都有一个极大值 ,总趋势是 ,各组分 ζ电势绝对值基本上随着盐浓度的增加而减小。碱性条件下 (pH =11～ 12 )水包稠油乳状液中起稳定作用的官能团组分主要是酸性分和极性四组分中的沥青质。水相的碱性条件有利于水包稠油乳状液的稳定 ,盐在特定浓度下具有一定的稳定水包稠油乳状液的作用。但从总体趋势看 ,盐含量的增加会破坏乳状液的稳定性。用离子交换色谱分离得到的官能团组分更能揭示稠油中界面活性组分的内在本质。

Zeta potential for heavy crude components and oil-water system

The oil-water zeta-potentials of heavy crude components from Liaohe and Shengli Gudao oilfields were investigated. The functional fractions including acid, basic, amphoteric fraction and neutral fraction were isolated from the heavy crude oils using ion-exchange chromatography. The conventional fractions including saturates, aromatics, resins and asphaltenes were extracted from the heavy crude oils. The influences of pH value and brine in water system on zeta-potential were discussed. It was verified that the oil-water zeta-potential difference among the conventional fractions could be neglected, but the contribution of acid fraction to the oil-water zeta-potential was predominated among the functional fractions. The zeta-potential of each fraction increased when the pH value rose, while it decreased when the salinity rose. The oil-water zeta-potential (-80mV)of acid fraction is the largest under the basic condition that pH value is in the range of 11 to 12. The interfacial activity of acid fraction is superior to that of the other fractions, and the basic condition for water phase is favorable to the stability of oil-in-water emulsion. Certain salinity concentration has some contribution to the stability of oil-in-water emulsion.