Spontaneous imbibition in porous media: comparisons between a dynamic
pore-network model and a VOF direct numerical simulation model
Abstract
The dynamic pore-network modeling, as an efficient pore-scale tool, has
been used to understand spontaneous imbibition in porous media, which
plays an important role in many subsurface applications. In this work,
we aim to compare a dynamic pore-network model of spontaneous imbibition
with the VOF (volume of fluid) model. The µCT scanning of a porous
medium of sintered glass beads is selected as our study domain. We
extract its pore network by using an open-source software of PoreSpy,
and further project the extracted information of individual watersheds
into multiform idealized pore elements. A number of case studies of
primary spontaneous imbibition have been conducted by using both the
pore-network and the VOF models under different wettability values and
viscosity ratios. We compare those model predictions in terms of
imbibition rates and temporal saturation profiles along the flow
direction. We show that the pore-network model can reproduce the VOF
model results for an air-water system, in which water is the wetting
phase. For a more viscous nonwetting phase such as oil, however, the
pore-network model predicts a slower imbibition process and a rougher
wetting front, in comparison to the predictions by the VOF model.