Footprints of spontaneous fluid redistribution on capillary pressure in porous rock

Abstract

Pore‐scale imaging of two‐phase flow in porous media shows that pore filling occurs as cooperative events with accompanying spontaneous fluid redistribution in other parts of the pore space. We present a level set method that controls saturation quasi‐statically to model experiments controlled by low, constant flow rates and demonstrate that our method can describe the observed displacement mechanisms. The level set approach determines states of capillary equilibrium, which generally are different for displacement protocols constrained by saturation and pressure. Saturation‐controlled simulations of drainage in sandstone show spontaneous fluid redistributions with abrupt pressure jumps and cooperative behavior, including snap‐off and interface retraction events, consistent with experimental observations. Drainage capillary pressure curves are lower when saturation, rather than pressure, controls displacement. Remarkably, these effects are less significant for imbibition processes where the development of hydraulically connected wetting phase moderates the cooperative behavior and associated pressure jumps.

Adhesion-force micro-scale study of desiccating granular material

“…Thus, with a REV large enough (several hundred grains) and timescales long enough, as is the case in many geomechanics applications, Haines jumps are confined to a 'drying front' and become relatively inconspicuous saw-toothing of the averaged pressure, which appears to be a continuous and monotonic function of time; see also Måløy et al (1992) and Georgiadis et al (2013). Thus, it is expected that, upon homogenisation, an intergranular macro-scale force also becomes a continuous function of saturation, or water content (Lenormand et al, 1983;Berg et al, 2013;Helland et al, 2017).…”

“…This assumption is questionable, as there is wide evidence to the contrary on the micro-scale, for both evaporation of sessile drops, and for drying bridges (Deegan et al, 1997; see also Yang et al, 2018). (b) Second, it has been noted in a number of recent meso-scale tests that the pressure-saturation relationship of evaporating (or variable saturation) media (SWCC curve) substantially depends on the driving variable, and hence it is different for pressure-driven, and for saturation-driven tests (Toussaint et al, 2012;Armstrong & Berg, 2013;Armstrong et al, 2015;Cueto-Felgueroso & Juanes, 2016;Helland et al, 2017). The present authors' tests qualify as environment-controlled tests, as constant temperature and constant relative humidity are imposed in a test chamber.…”

Energy Conversion Reveals Regime Transition of Imbibition in a Rough Fracture

“…Since energy balance is independent of system size and flow geometry, it offers a rigorous way for identification of the transitions between the two regimes. Energy conversion and dissipation have been investigated by experiments (Morrow, 1970;Schlüter et al, 2017;Seth & Morrow, 2006) and simulations (Ferrari & Lunati, 2014;Helland et al, 2017;Zacharoudiou et al, 2017). In a pioneering experimental work, Morrow (1970) discussed the energy conversion between surface energy and external work, indicating that during capillary imbibition, only part of surface energy can be converted into external work and the rest is dissipated.…”

Intermittent Dynamics of Slow Drainage Experiments in Porous Media: Characterization Under Different Boundary Conditions

“…The topic of multiphase flow in porous media has received widespread attention by the scientific community in the past decades [1][2][3][4][5][6][7][8][9][10][11]. In addition to its inherent physical interest (pattern formation [12][13][14][15][16][17][18], intermittent dynamics [3,[19][20][21][22][23][24], collective phenomena [25][26][27][28][29], etc. ), the topic naturally receives focus due to its immediate industrial and environmental applications.…”