Linking continuum-scale state of wetting to pore-scale contact angles in porous media

Abstract

Hypothesis:Wetting phenomena play a key role in flows through porous media. Relative permeabilityand capillary pressure-saturation functions show a high sensitivity to wettability, which has differentdefinitions at the continuum- and pore-scale. We hypothesize that the wetting state of a porous mediumcan be described in terms of topological arguments that constrain the morphological state of immisciblefluids, which provides a direct link between the continuum-scale metrics of wettability and pore-scalecontact angles.Experiments:We perform primary drainage and imbibition experiments on Bentheimer sandstone usingair and brine. Topological properties, such as Euler characteristic and interfacial curvature are measuredutilizing X-ray micro-computed tomography at irreducible air saturation. We also present measurementsfor the United States Bureau of Mines (USBM) index, capillary pressure and pore-scale contact angles.Additional studies are performed using two-phase Lattice Boltzmann simulations to test a wider rangeof wetting conditions.Findings:We demonstrate that contact angle distributions for a porous multiphase system can be pre-dicted within a few percent difference of directly measured pore-scale contact angles using the presentedmethod. This provides a general framework on how continuum-scale data can be used to describe thegeometrical state of fluids within porous media. Show more