Dynamic Effects in Oil/Water and Air/Water Capillary ...

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XVI International Conference on Computational Methods in Water Resources (CMWR-XVI) Ingeniørhuset

Dynamic Effects in Oil/Water and Air/Water Capillary Pressure-Saturation Curves: Experiments and Lattice-Boltzmann Simulations
Author:Mark Porter <porterm@geo.oregonstate.edu> (Oregon State University)
Marcel Schaap <mschaap@ussl.ars.usda.gov> (GEBJ Salinity Laboratory)
Dorthe Wildenschild <wildend@geo.oregonstate.edu> (Oregon State University)
Presenter:Mark Porter <porterm@geo.oregonstate.edu> (Oregon State University)
Date: 2006-06-18     Track: Special Sessions     Session: Pore-Scale Modelling: New Developments And Applications

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.