Pore-Scale Study of the Effect of the Saturation History on Fluid Saturation and Relative Permeability of Three-Fluid Flow in Porous Media

Abstract:

The flow of three immiscible fluids - water, NAPL, air - in porous media is important in many subsurface processes. To model the three-fluid flow, the relation of relative permeability-saturation-capillary pressure (k-S-P) of three fluids is of central importance. In this experimental study, we directly measure the k-S-P of the water (wetting phase) when three fluids are coexist in a micromodel during the water drainage and imbibition.

The results show that the sequence of the non-wetting fluids (air and NAPL) entering into the micromodel affects the fluid distributions as well as the relative permeability of water. During the drainage process, the relative permeability of water dropped drastically when the pathway of water from inlet to outlet of the micromodel was visually blocked by the non-wetting fluids. At this stage, the relative permeability of water was low but not down to zero. The water was still able to move via corner flows or thin-film flows. During the imbibition process, the water displaced two non-wetting liquids via both "snap-off" and "piston-type" motions. The relative permeability of water jumped when the water pathway was formed again. In addition, we found that the well-known scaling format proposed by Parker et al. [1] might fail when the interfaces between the most non-wetting (air) and the most wetting (water) fluids occurs in the three-fluids system.

References
[1] J. C. Parker, R. J. Lenhard, and T. Kuppusamy, Water Resources Research, 23, 4, 618-624 (1987)