Abstract: Aiming at the insufficient understanding of the multiphase fluid microscopic seepage laws after crude oil emulsification in chemical flooding, the lattice Boltzmann method was used to describe the seepage behavior of the continuous phase fluid, combined with the immersed boundary method to describe the migration behavior of emulsion droplets. The mechanical equation for elastic deformation of emulsion droplets was introduced to establish a mathematical model for emulsion droplet seepage at the micro-pore scale. Through numerical simulation of heterogeneous pores, the transport and deformation characteristics of emulsion droplets with different particle sizes, viscosities and elasticities in pores were studied. The fluid diversion behavior after emulsion droplets form retention plugging in large pores was quantitatively analyzed and the influence of the interfacial rheological properties of emulsion droplets on fluid seepage in heterogeneous pores was clarified. The results indicate that the fluid diversion effect after plugging is obvious when the emulsion droplet size is close to or larger than the pore size; high viscosity and high elasticity droplets increase the fluctuation amplitude of the surrounding fluid seepage velocity, and significantly reduce the fluid seepage velocity and flow rate in the pore; the contribution rate of the emulsion droplet size factor (particle sizes of 3 and 8 μm) to expanding the sweep volume is 6.99%, the contribution rate of the emulsion droplet viscosity factor (viscosity ratio of droplet to external continuous phase of 1 and 5) is 3.46%, and the contribution rate of the emulsion droplet elasticity factor (elastic parameters of 200 and 70) is 6.75%. The research results are of great significance for clarifying the mechanism of emulsion profile control and flooding.

Key words: chemical flooding, emulsion, microfluidics, microscopic seepage, lattice Boltzmann