Research on Oil Displaced Effect of Multi‐Component Pore‐Throat Emulsion System

Abstract

The core displacement experiment is designed to simulate the emulsification process of crude oil in reservoir, and a multi‐component pore‐throat emulsion system (0.8% hexadecane fluorinated betaine (CFN) + 0.4% sodium dodecylbenzenesulfonate (SDBS) + 1.2% monodisperse partially hydrophobic silanized SiO2 solution (particle diameter of 25 nm) + 0.9% sodium chloride (NaCl)), system 1, was developed. By comparing this system with the other emulsion systems, the stability and comprehensive performance of this system were evaluated. The results showed that the water evolution rate of emulsion system 1 was the smallest, 46.3%, which indicated that the stability of system 1 was the best, and the synergistic ability of emulsifiers CFN and SDBS was effective. After alkylation, nano‐sized SiO2 particles are turned into a special structure of hemispheric hydrophobic and hemispheric hydrophilic. They are closely adsorbed on oil‐water interface, which can inhibit the aggregation between emulsion drops and enhance the stability of emulsion. The micro particle size of emulsion was observed using inverted biological microscope, and it was found that the range of system 1 was the smallest. And microscopically or macroscopically, the properties such as the average diameter of the droplet, separation coefficient, effective share of the droplet, emulsion strength and stability comprehensive coefficient, were dominant. Therefore, the performance of system 1 was well. The displacement effect of emulsion flooding and change of fluid production in each layer under different permeability contrast were researched by three‐tube parallel core displacement experiment. It was found that oil displacement effect of system 1 was the best, the greater the coefficient of permeability variation, the greater decline of liquid production in the high permeability reservoir, and the greater increase of liquid production in the middle and low permeability reservoir. The new emulsion flooding system provides a new idea for the development of heterogeneous reservoirs.

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