The capillary pressure-saturation curve is widely used to characterize hydraulic
properties of porous media.  It is often assumed that curves measured under
equilibrium or steady-state flow conditions can be applied to transient flow
conditions, and vice versa.  Yet, substantial experimental evidence suggests that
capillary pressure-saturation curves obtained during transient conditions differ from
those obtained under equilibrium or steady-state conditions.  It has been shown that
the capillary pressure-saturation curve shows signs of dynamic behavior depending on
the inflow and outflow rate applied to the porous system. The exact cause of the
observed shift is not yet fully understood.  It is hypothesized that the mechanisms
responsible for dynamic behavior include: (1) the geometry of the pore space, (2)
interfacial phenomena at the pore scale, and (3) the interplay of inertial and
viscous forces.

In this investigation, air/water and oil/water imbibition and drainage experiments
were conducted on a column of packed glass beads.  Various inflow and outflow rates
were applied to each multi-phase system, which resulted in capillary
pressure-saturation curves that exhibit varying degrees of dynamic behavior.  The
dynamic behavior observed in preliminary oil/water experiments was less pronounced
than the behavior observed in past air/water experiments.  This suggests that the
viscous and inertial forces may only be a major factor when the density and viscosity
ratios are large, as is the case for the air/water system. 

The dynamic behavior was examined using conceptual 2D and 3D lattice-Boltzmann (LB)
simulations. We used the multi-phase, multi-component model developed by Shan and
Chen for these simulations. The conceptual LB simulations can provide insights into
pore-scale interfacial phenomena and help explain the dynamic behavior observed in
the experiments.  Scaling of time and space from LB parameters to physical parameters
was performed to make comparisons between simulation and experimental results possible.

Ingeniørhuset, Kalvebod Brygge 31-33, 1780 Cph. V