Snap-off Time for Continuous Nonwetting Liquids in Sinusoidally Constricted Pores
Thursday, 18 December 2014
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.