Optimizing Middle-Phase Microemulsions for Enhanced Oil Recovery: An HLD-NAC Theoretical Framework and Experimental
Wenjie Tang1,2, Patiguli Maimaiti1,2, Hongzhi Shao1,2
1Research Institute of Exploration and Development, Xinjiang Oilfield Company, PetroChina, Karamay 834000, Xinjiang, China.
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Middle-phase microemulsions (Winsor III) are critical for enhanced oil recovery (EOR) due to their ultralow interfacial tension (IFT) and high oil solubilization capacity. In this study, hydrophilic-lipophilic deviation (HLD) and net average curvature (NAC) theories were employed to design a salinity-optimized microemulsion system using coconut oil diethanolamide (6501) for a specific crude oil. Emulsification tests confirmed that increasing salinity expanded the middle-phase volume, while low salinity favored Winsor I (O/W) microemulsions. Polymer destabilized middle-phase formation but improved recovery by 40-45% due to enhanced sweep efficiency. Core flooding revealed that traditional surfactant-polymer (SP) flooding outperformed salinity-tuned microemulsions, likely due to insufficient oil-surfactant mixing after water flooding. Results of this work provide a framework for optimizing microemulsion-based EOR processes through integrated theoretical and experimental approaches and offer potential optimization strategies for field-scale application.
