Influence of Organic Acid Solution Chemistry on Subsurface Transport Properties. 2. Capillary Pressure−Saturation

Abstract

Two-phase flow models of subsurface transport often require the constitutive relationship of capillary pressure as a function of saturation as part of the data input. This part of the study correlates the solution chemistry findings from the previous paper with observed changes in the primary drainage capillary pressure−saturation relationship for a fine- to medium-grained quartz porous medium. The results showed that the solution chemistry was directly reflected in the capillary pressure−saturation relationship. The major factor determining the degree of reduction in capillary pressure was the concentration and speciation of octanoic acid dissolved in the aqueous phase, the same variables reported in part 1 as critical in determining the surface and interfacial tension. Because measurements of the contact angle showed that the system stayed strongly hydrophilic under all conditions, the capillary pressure relationships could be scaled adequately using the appropriate values of surface or interfacial tension only. Since organic acid speciation had opposite effects on capillary pressure in the air−water and o-xylene−water systems, the impact of pH on the movement of a contaminant front will depend on whether the contamination occurs in the vadose zone (air−aqueous phase system) or saturated zone (organic liquid−aqueous phase system).

Interfacial Properties and Partitioning of 4-Heptylbenzoic Acid between Decane and Water

“…It should be noted that the ISG model is limited to considering changes in IFT with pH as a purely electrostatic effect. As has been shown by Rudin and Wasan (20) such a model will not be able to describe the occurrence of a minima in IFT which has been reported by several authors (14,17,18). However, within its limitations it is likely to give a better description of the changes in the degree of ionization at the interface than other models based on the same assumption (19,25,26), because it gives a better description of the ion distribution near an oil/water interface with a given density of charged sites.…”

Preferential flow systems amended with biogeochemical components: imaging of a two-dimensional study

“…where P C is for the capillary pressure, γ and θ are the surface tension and contact angle of a solution, respectively, and r is the radius of the pore size of the medium (Lord et al, 1997). Modeling approaches have been developed to assess the relationships between particle sizes and pore size distributions in porous media constituted by multicomponent particles (Assouline and Rouault, 1997).…”

On Capillary Slowdown of Viscous Fingering in Immiscible Displacement in Porous Media

“…Two-phase flow models of subsurface transport often require constitutive relationship of capillary pressure as a function of saturation (Lord et al 1997). Leverett defined a reduced capillary function containing parameters such as permeability, porosity, contact angle, surface tension, and used for correlating capillary pressure data (Dullien 1992).…”

“…Instead, governing equations admit a uniformly moving smooth traveling wave as a solution whose structure depends crucially on the relation between capillary pressure and saturation. Capillary pressure is a non-linear function of saturation (see Lord et al 1997) which makes the governing parabolic equations highly non-linear. This complicates even the linear stability analysis of such simple basic solutions.…”