Spontaneous Emulsification via Once Bottom-Up Cycle for the Crude Oil in Low-Permeability Reservoirs

The formulation and mechanism of a hybrid ultralow interfacial tension spontaneous emulsification (SE) system consisting of alkyl polyglucoside surfactant and low-concentration alkali were investigated to enhance oil recovery for low permeability reservoirs. Multiple-light scattering was used to characterize the stability and demulsification process of oil-in-water (O/W) emulsions. The emulsions were evaluated in terms of droplet size distribution, zeta potential, and three-phase rheological property. The average droplet size of the optimum SE O/W emulsion is about 0.2 mu m, which is smaller than the average diameter of the low-permeability throats (0.2-4.0 mu m). The coalescence and floatation of emulsion droplets are well-deferred. The oscillation-shear-oscillation rheological property could be further improved with the presence of the optimum system. This can be attributed to the synergistic effect of surfactants and alkali, which enables the formation of a more tight arrangement film of surfactants at the oil-water interface. Subsequently, diffusion of the surfactant from the interface to the bulk phase is inhibited by enhancing the interfacial viscosity. Moreover, the flooding results from the visual micromodel experiments demonstrate that the small residual oil droplets could be displaced easily in the porous media. The newly formulated SE system can be applied to enhance oil recovery for low-permeability reservoirs.