Snap-off Time for Continuous Nonwetting Liquids in Sinusoidally Constricted Pores

Abstract:

Snap-off is an important dynamic phenomenon for multiphase flow in porous media. It contributes to oil or CO₂ residual trapping and foam generation in foam flooding. Current applied and theoretical studies of snap-off have mostly focused on static criterion that determines if snap-off will occur. The dynamics of snap-off process has seldom been studied and thus poorly understood. While the snap-off criterion indicates the potential for nonwetting fluids to snap off, the competition between the time required for snap-off (snap-off time) and the discharge at local pores determines the eventual occurrence of snap-off. Here, snap-off time and shape are investigated with respect to pore throat to pore body aspect ratio, pore body distances, local discharge, wetting/nonwetting fluids viscosity ratio, and wetting film thickness. The analysis is conducted through a theoretical model that has been validated by computational fluid dynamics simulations. Predictive equations of snap-off time as functions of the above factors are developed. The predictive equations of snap-off time can be applied to current two-phase dynamic pore-network models to improve continuum models for relative permeability and residual saturation.