Low-energy formation of in-situ nanoemulsion at constant temperature for oil removal

Nanoemulsions have great potential in oil clingage removal. However, the stability and rheological properties of nanoemulsions is difficult to control, which limits their application. In this paper, the performance of in-situ nanoemulsions formation when surfactant solution contact with oil was investigated, leading to a novel idea of oil removal using nanoemulsions. It is found that the reduction of interfacial tension due to surfactant migration from the initial phase to the interface is the critical step for the formation of nanoemulsions. Therefore, on the basis of proper adjustment of the affinity between surfactant and oil/water phase, the nanoemulsion was formed by dropping oil into the surfactant solutions, which is similar to the case where the surfactant solution contact with the oil clingage. The affinity is greatly affected by the hydrophilic-lipophilic balance of surfactant and the polarity of oil and water phase. Moreover, the formation of nanoemulsion by this method also depends on the oil-water ratio and energy input. The nanoemulsions formed have high stability and good fluidity, which is beneficial for the flowback of flushing liquid. It is hoped that this research can provide supplement for the low-energy preparation of nanoemulsions and provide theoretical basis for broadening the application scope of nanoemulsions.