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<p>During chemical flooding, crude oil readily forms emulsions upon contact with injected fluids. The associated phase transition, interfacial microstructural evolution, and stability variation can significantly affect oil–water interfacial behavior and flow characteristics. To clarify the underlying mechanisms under different chemical conditions, this study investigated emulsions formed between dehydrated crude oil and produced wastewater, salt solutions, alkali solutions, polymer solutions, surfactant systems, alkali–surfactant systems, and alcohol solutions. Confocal laser scanning microscopy, droplet size analysis, and rotational rheological measurements were used to systematically evaluate the effects of chemical type, concentration, water cut, and crude-oil SARA fractions on emulsion properties. The results show that water cut is the dominant factor controlling emulsion phase behavior, while chemical type further affects the phase inversion point and microstructural evolution. Resins and asphaltenes, as the main natural surface-active components, participate in interfacial-film formation and influence emulsion stability. Overall, salt systems more readily promote emulsion destabilization; alkali systems inhibit droplet coarsening to some extent; polymer systems show relatively limited effects; alkali–surfactant systems exhibit pronounced concentration dependence; and alcohol systems contribute to emulsion stability. The rheological results mainly reflect the bulk rheological behavior of emulsions, and all systems exhibit shear-thinning characteristics. These findings provide a theoretical basis for phase-state regulation and stability evaluation of crude oil emulsions during chemical flooding.</p>

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Chemical regulation of phase inversion, interfacial microstructure, and rheological behavior in crude oil emulsions

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • Yuchen Wang,
  • Qiansong Guo,
  • Xianda Sun,
  • Chunjing Lu,
  • Limin Suo,
  • Wenjun Ma

摘要

During chemical flooding, crude oil readily forms emulsions upon contact with injected fluids. The associated phase transition, interfacial microstructural evolution, and stability variation can significantly affect oil–water interfacial behavior and flow characteristics. To clarify the underlying mechanisms under different chemical conditions, this study investigated emulsions formed between dehydrated crude oil and produced wastewater, salt solutions, alkali solutions, polymer solutions, surfactant systems, alkali–surfactant systems, and alcohol solutions. Confocal laser scanning microscopy, droplet size analysis, and rotational rheological measurements were used to systematically evaluate the effects of chemical type, concentration, water cut, and crude-oil SARA fractions on emulsion properties. The results show that water cut is the dominant factor controlling emulsion phase behavior, while chemical type further affects the phase inversion point and microstructural evolution. Resins and asphaltenes, as the main natural surface-active components, participate in interfacial-film formation and influence emulsion stability. Overall, salt systems more readily promote emulsion destabilization; alkali systems inhibit droplet coarsening to some extent; polymer systems show relatively limited effects; alkali–surfactant systems exhibit pronounced concentration dependence; and alcohol systems contribute to emulsion stability. The rheological results mainly reflect the bulk rheological behavior of emulsions, and all systems exhibit shear-thinning characteristics. These findings provide a theoretical basis for phase-state regulation and stability evaluation of crude oil emulsions during chemical flooding.