Phenomenological study of the micro- and macroscopic mechanisms during polymer flooding with SiO2 nanoparticles

The incorporation of SiO2 nanoparticles in polymer solutions for oil recovery has generated considerable interest in recent research. Although this approach improves the polymer performance, little evidence is available about the recovery mechanisms that intervene in the polymeric nanofluid suspension or polymer nanofluid. Therefore, the purpose of this study is to describe the microscopic and macroscopic mechanisms involved during oil recovery with polymeric nanofluid flooding. Changes in the rheology and capillary forces (contact angle and interfacial tension) in the polymeric solution due to the incorporation of SiO2 nanoparticles were evaluated. Coreflooding tests were made to evaluate the retention, apparent viscosity, and impact on the relative permeability. Finally, macroscopic oil recovery was measured by displacement tests in a quarter 5-spot system, and microscopic displacement was evaluated by a microfluidic test. Results indicated that the conservation of a favorable mobility ratio in polymeric nanofluids along the porous medium is the phenomenon that most impacts macroscopic oil recovery. This behavior was associated with a reduction in loss retention and the conservation of the apparent viscosity in the porous medium. A direct relationship was observed between the concentration of SiO2 nanoparticles and the viscoelastic behavior of the polymer and the water-wet condition on the surface exposed to the nanofluid. Moreover, residual oil distribution in microscopic displacement revealed that the reduction in residual oil mainly originated from the decrease in the size of the oil clusters. Consequently, the evidence suggests that microscopic oil displacement in polymeric nanofluid is attributed to the reduction in the capillary forces and increases in the viscoelastic nature of the polymer. Results in this work indicated that the additional oil recovery obtained by polymeric nanofluid flooding is generated by the improvement of macroscopic recovery mechanisms and the activation of microscopic mechanisms.

Automated summary

The research indicates that maintaining a favorable mobility ratio is the key macroscopic factor in oil recovery with polymeric nanofluids, while the concentration of SiO2 nanoparticles directly relates to the viscoelastic behavior of the polymer and the water-wet condition. Microscopic displacement results show that residual oil mainly originates from the decrease in the size of the oil clusters.