Abstract:

Water-in-heavy oil（heavy W/O）emulsions widely exist in the petroleum exploration and petrochemical processing. Due to their high viscosity, high density, and strong interface stability, the separation of heavy W/O emulsions is fairly difficult, inevitably leading to an increasing cost in production. To enhance the separation efficiency of heavy W/O emulsions, in this study, the influence of temperature and toluene addition on the viscosity of heavy oil was systematically investigated. On this basis, the synergistic mechanism between viscosity reduction and dehydration ratio was discussed. A proposed TJU-3 demulsifier was used to break the heavy W/O emulsions. The optimal process conditions were obtained by varying the demulsifier concentration and the demulsification temperature. The molecular simulation method was used to build the heavy oil average molecular model and calculate the diffusion coefficient of SARA in the heavy oil with different content of toluene. The effect of toluene on the interaction of SARA in heavy oil was analyzed and the transport process of asphaltenes and TJU-3 demulsifier molecules at oil-water interface was studied. The results showed that a complete demulsification could be achieved within 1h when the viscosity of the heavy oil was reduced to 1500mPa·s. When the viscosity was reduced to 50mPa·s, the demulsification could be completed within 20min. When the concentration of demulsifier in the emulsions was 400mg/L, the dehydration ratio of the emulsions was the highest. When demulsification temperature was 60℃, demulsification rate was the highest. The diffusion coefficient of resins increased most significantly in SARA components, which was the main reason that the viscosity of heavy oil could be rapidly reduced by toluene. The TJU-3 demulsifier could break the asphaltene interface film, which achieved the demulsification of heavy W/O emulsions. The synergistic mechanism and technological conditions can provide reference for rapid demulsification of heavy W/O emulsion at low temperature in petroleum industry.

Key words: water-in-heavy oil emulsions, demulsification, toluene, viscosity reduction, molecular simulation, asphaltenes

摘要：

重质油包水（W/O）乳液普遍存在于石油开采与加工过程中，因其高黏度、高密度、强界面稳定特性，导致重质油包水乳液分离困难，生产成本增加。为了提高重质W/O乳液的分离效率，本文探究了温度与甲苯加入量对重质油黏度的影响规律。在此基础上，研究了上述降黏过程与脱水率之间的协同机制。采用自制的TJU-3破乳剂对重质W/O乳液进行破乳，通过调整破乳剂在乳液中的浓度和破乳温度得到了最佳工艺条件。利用分子模拟的方法构建了重质油平均分子模型并计算了SARA四组分在不同甲苯含量的重质油中的扩散系数，分析了甲苯添加量对重质油中SARA四组分相互作用的影响规律，研究了沥青质分子和TJU-3破乳剂分子在油水界面的运移过程。结果表明：重质油的黏度降低到1500mPa·s时，可实现在1h内完全破乳；黏度降低到50mPa·s时可实现在20min内完全破乳。当破乳剂在乳液中的浓度为400mg/L时，乳液的脱水率最高；破乳温度为60℃时，破乳速度最快。SARA四组分中胶质的扩散系数增大最显著，是重质油的黏度能被甲苯迅速降低的主要原因。TJU-3分子能够破坏沥青质界面膜，进而实现破乳。该协同机制和工艺条件可为石油工业中重质W/O乳液的低温快速破乳工艺提供参考。

关键词: 重质油包水乳液, 破乳, 甲苯, 降黏, 分子模拟, 沥青质