难破乳采出液的乳化影响因素及量化分析

Emulsification Influencing Factors and Quantitative Analysis of More Hard-demulsifying Produced Liquid

聚合物驱采出液的乳化程度提高、破乳脱水难度增加。以胜利油田孤岛聚合物驱难破乳采出液和正常破乳时的采出液为研究对象,通过油水样性质参数对比分析、交叉乳化及破乳实验和乳状液微观形态变化分析导致聚合物驱采出液破乳难度增加的关键因素,同时借鉴胶体聚沉理论,量化了其内在因素对乳化的影响程度。研究结果表明:高价金属阳离子和烷基苯磺酸盐表面活性剂的相互作用是导致破乳困难的关键因素;降低高价金属阳离子浓度,原油乳状液的破乳脱水率大幅度提高;以十二烷基苯磺酸钠为乳化剂配制的O/W型乳状液,加入Fe^(3+)后O/W乳状液稳定性变差,出现向W/O型乳状液变化的趋势。参考胶体聚沉理论定义了金属阳离子影响参数M,孤岛原油乳状液M的临界阈值为214 mmol/kg,表面张力的临界阈值为45 mN/m,当M大于214 mmol/kg且表面张力小于45 mN/m时孤岛乳化体系难破乳。

The demulsification and dehydration was more difficulty with the increasing emulsification degree of polymer flooding produced liquid.Taking the produced fluid of polymer flooding of difficult-to-demulsify and normal demulsification in Shengli Oilfield as the research object,the key factors leading to the increase of demulsification difficulty were analyzed by comparing the properties of oil and water samples,cross emulsification and demulsification experiments and microscopic morphology changes of emulsion.At the same time,the influence of internal factors on emulsification was quantified by referring to the theory of colloidal coagulation.The results showed that the interaction between the high valence metal cations and alkylbenzene sulfonate surfactants was the key factor leading to the difficulty of demulsification.In the cross demulsification experiment,the concentration of high valence metal ions was reduced,and the demulsification dehydration rate of crude oil emulsion was greatly improved.The O/W emulsion was prepared with sodium dodecyl benzene sulfonate as emulsifier.After adding Fe^(3+),the stability of O/W emulsion became worse,and it showed a tendency to change to W/O emulsion.The critical threshold of M of Gudao crude oil emulsion was 214 mmol/kg,and the critical threshold of surface tension was 45 mN/m.