Drainage in a model stratified porous medium
Department of Physics, Harvard University - Cambridge, MA 02138, USA
Received: 31 October 2012
Accepted: 11 December 2012
We show that when a non-wetting fluid drains a stratified porous medium at sufficiently small capillary numbers Ca, it flows only through the coarsest stratum of the medium; by contrast, above a threshold Ca, the non-wetting fluid is also forced laterally, into part of the adjacent, finer strata. The spatial extent of this partial invasion increases with Ca. We quantitatively understand this behavior by balancing the stratum-scale viscous pressure driving the flow with the capillary pressure required to invade individual pores. Because geological formations are frequently stratified, we anticipate that our results will be relevant to a number of important applications, including understanding oil migration, preventing groundwater contamination, and sub-surface CO2 storage.
PACS: 47.56.+r – Flows through porous media / 47.61.Jd – Multiphase flows / 47.80.Jk – Flow visualization and imaging
© EPLA, 2013