Oil Displacing Mechanism of Soft Microgel Particle Dispersion in Porous Media

The formation heterogeneity causes uneven sweeping of waterflooding. Different degrees of prevailing water flowing are generated due to different sizes of pores and throats. During the middle-late stage of water flooding, it is hard to move the remaining oil since it is scattered in the pores and throats. The EOR (enhanced oil recovery) study is mainly concerned with methods both to inhibit different sized prevailing flowing channels, and to keep oil flowing path free of plugging, which can ensure production efficiency of remaining oil. In this study, the pore-scale microscopic heterogeneous models with real pore structure were established, and different oil displacing mechanisms were compared between continuous phase viscous fluid, such as conventional polymer and crosslinked polymer gel, and micro-nano soft microgel particle dispersion. Results show that the traditional polymer flooding cannot differentiate between high and low permeability or big and small pore, because it relies on viscosity to increase the flowing resistance of all the swept area and it is hard to move the remaining oil when the viscosity is high to some extent. The soft microgel particle dispersion is a type of low viscosity dispersion fluid, and the particles have priority to access relatively big pore and throat, to temporarily inhibit the flowing, and at the same time, the water can be diverted into the relatively small pore and throat, to push the remaining oil out as a piston. The process is repeated continuously. The lab results were analyzed from the view of mobility adjustment in this paper, and it is concluded that the conventional continuous phase driving fluid modified mobility by increasing injection water viscosity, while the soft microgel particle dispersion achieved efficient mobility adjustment by decreasing the relative permeability of injection water and accordingly increased the oil permeable ability.