Study on emulsification performance evaluation and oil displacement effect of different emulsion composite systems
The stability,viscosity,and micro-morphological changes of emulsions formed by different com-posite systems under core seepage and mechanical stirring were studied from macro and micro perspec-tives by using a universal infrared stability analyzer,optical microscope,and multifunctional rheometer.On this basis,the oil displacement effect of different emulsion composite systems was studied by core flooding experiments.The results show that the binary system of betaine surfactant can effectively generate emul-sion in the process of core porous media flooding,and the stability of different composite systems under mechanical stirring is significantly different.The mechanical stirring shear of binary,alkali-free A,and ter-nary systems have an inverse correlation with the TSI value of the emulsion formed by core seepage,while the two methods have a positive correlation in the viscosity of the emulsion.Compared with core shearing,the shear stress of mechanical stirring is larger,and the particle size of emulsion droplets generated by dif-ferent systems is smaller,which can more significantly distinguish the difference in emulsion phase state between different systems.In the process of the core flooding experiment,there is an inverse correlation between the overall seepage resistance and the enhanced oil recovery(EOR).The magnitude of enhanced oil recovery in different systems increases in turn and has significant gradient differences.The binary,ter-nary,and alkali-free A system can not only play a profile control role through emulsification and plugging but also expand the swept volume and improve the efficiency of oil washing.Notably,emulsified fluid can also enter the micro-pore area that is difficult to be affected by water flooding to wash oil and scrape oil,reduce residual oil saturation through emulsification and carrying,and improve the oil displacement effect.
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