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, ζ potential, and three-phase
rheological property. The average droplet size of the optimum SE O/W
emulsion is about 0.2 μm, which is smaller than the average
diameter of the low-permeability throats (0.2–4.0 μm).
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.
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