Deformation dynamics of rear concave droplet enclosed by nanoparticle surfactants in a capillary

In oil reservoirs with high water-cut, residual oil droplets are dominant and noticeable rear concave deformed when mobilizing in capillaries. The “solid-like” interface was exhibited by nanoparticle surfactants (NPSs) adsorbed in nanoparticles flooding. Related specific interfaces (i.e., phospholipid bilayer and nanoparticles adsorbed interface) have demonstrated their influences on droplet dynamics, e.g., elastic modulus related breathing, and Marangoni stress induced deformation. However, the constitutive mechanical characteristics of the NPSs adsorbed interface still differ from them, resulting in that the deformation dynamics of rear concave droplets enclosed by NPSs is not fully understood. A Neo-Hookean model was employed to simulate the elastic interface adsorbed by NPSs. The effects of the elastic interface on the droplet deformation dynamics were examined on three typical rear concave droplets. The results indicate that the elastic interface exerts a great inhibitory effect on the rear concave droplet deformation: for droplets with rear jet penetration, the inhibitory effect is only significant at droplet tail; for droplets with shear-induced tail breakup, the inhibitory effect appears both at droplet tail and head; and for droplets with steady rear concave, only droplet head deformation is inhibited. As viscosity ratio increased, the inhibitory effect of elastic interface on droplet deformation shifts from droplets tail to head. These findings significantly contribute to our understanding of droplet deformation dynamics within reservoir pores and hold great importance for optimizing nanoparticles flooding processes.