Comparison of Average and Point Capillary Pressure–Saturation Functions Determined by Steady‐State Centrifugation

Abstract

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Comparison of Average and Point Capillary Pressure-Saturation Functions Determined by Steady-State Centrifugation Soil Physics T he capillary pressure-saturation function is an important hydraulic property of variably saturated rocks and soils. Th is function is needed for simulating multiphase fl uid fl ow and chemical transport in porous media in applications such as agricultural crop production, enhanced oil recovery, subsurface C sequestration, and remediation of contaminated soils. In soil physics, the capillary pressure-saturation function is traditionally determined in the laboratory using a hanging water column (Dane and Hopmans, 2002a) or pressure plates (Dane and Hopmans, 2002b). In these methods, a series of capillary pressures, ψ, are imposed at a particular point and the corresponding volumetric water contents for the entire porous medium, 〈θ〉, are determined gravimetrically or manometrically. If the densities of the nonwetting and wetting fl uids are diff erent, ψ will vary with height within the porous medium (Dane et al., 1992; Liu and Dane, 1995a). As a result, the volumetric water content at the point where ψ is controlled, θ, can deviate signifi cantly from the measured 〈θ〉. Th us, use of the capillary pressure-average saturation function, 〈θ〉(ψ), instead of the point capillary pressure-saturation function, θ(ψ), in fl ow and transport models can produce erroneous predictions of important hydraulic properties such as the relative permeability function (Peters and Durner, 2006). Because point measurements of θ are rarely available in hanging water column and pressure plate experiments, computational procedures have been developed to extract the θ(ψ) function from the measured 〈θ〉(ψ) function. Liu and Dane

A new method to estimate location and slip of simulated rock failure events

“…Phase permeability varies between 0 and 1. It can be linked to the saturation S using van Genuchten relationships, which show very good agreement with experimental data for water and air mixture (Cropper et al, 2011;van Genuchten, 1980).…”

Comparison of the predictions of universal scaling of the saturation dependence of the air permeability with experiment

“…It is known that finite size and accessibility effects [ Larson and Morrow , 1981; Ewing and Gupta , 1993; Cropper et al , 2011], both treatable within the framework of percolation theory (first two references), confound the attempts to interpret the SWRC at high moisture contents in terms of a distribution of pore sizes that is independent of system size. Hunt and Gee [2003], however, did show that a water fraction closely related to ϕ − θ i , but extracted by identifying a deviation from fractal scaling of the SWRC, was typically slightly smaller than the water content at which solute diffusion vanished [ Moldrup et al , 2001].…”

Sensitivity of injection costs to input petrophysical parameters in numerical geologic carbon sequestration models

“…Of the capillary pressure-saturation parameters, the m exponent has been shown to be the most sensitive to the estimation method employed (Cropper et al, 2011). Furthermore, only a few capillary pressure versus saturation data sets are currently available for CO 2 gas or supercritical CO 2 displacing water or brine in porous media (e.g., Chalbaud et al, 2007;Plug and Bruining, 2007).…”

“…The range of porosity values tested was based on the simulation studies conducted by Doughty (2010) and Han et al (2011). The van Genuchten m values came from the study by Cropper et al (2011) and represent both different porous media and measurement methods. The other parameters were simply varied stepwise over reasonable ranges suggested by the literature (Gragg, 2012).…”