Capillary Pressure-saturation Relationship Research Articles

Effects of Organic Base Chemistry on Interfacial Tension, Wettability, and Capillary Pressure in Multiphase Subsurface Waste Systems

The presence of surfactants may have profound effects on the transport of organic contaminants in multiphase systems. It is a common practice, however, to model the subsurface migration of liquids independently of the aqueous phase composition. As such, transport in these systems may not be adequately characterized. This study investigates the impact of pH on interfacial tension, wettability, and the drainage capillary pressure–saturation relationship in air–water–quartz and o‐xylene–water–quartz systems containing dodecylamine, an organic base. In these systems, three mechanisms, speciation, partitioning, and sorption, are important in determining the interfacial tension and contact angle, and consequently, important in determining the capillary pressure. By adjusting the pH above and below, the pKa of the base, the relative importance of these mechanisms was altered. Below dodecylamine's pKa of 10.6, the base was primarily in a cationic form resulting in minimal partitioning into the nonaqueous liquid and greater sorption at the quartz surface. Above the pKa, the base was primarily in a neutral form which did not sorb to the quartz, and, furthermore, partitioned into the organic liquid phase where its surface activity was minimized. The combination of these processes caused the capillary pressure to change in a manner consistent with pore‐scale theory of capillarity. The utility in this approach lies in the possibility of predicting transport properties in multiphase systems while incorporating the direct effects of solution chemistry.

Node-centered finite volume discretizations for the numerical simulation of multiphase flow in heterogeneous porous media

Three node-centered finite volume discretizations for multiphase porous media flow are presented and compared. By combination of these methods two additional discretization methods are generated. The ability of these schemes to describe flows at textural interfaces of different geologic formations is investigated. It was found that models with nonzero-entry pressures for the capillary pressure-saturation relationship in conjunction with the Box discretization may give rise to spurious oscillations for flows around low permeable lenses. Furthermore, the applicability and sensitivity of the discretization methods with regard to the used computational grids is discussed. The schemes are used for the numerical study of two-phase flow in porous media with zones of different material properties.

Pressure Cell for Measuring Capillary Pressure Relationships of Contaminated Sands

A conventional pressure cell may be inadequate for making the multiple capillary pressure–saturation relationships necessary to characterize waste sites because of its materials of construction and poor dynamic response. This paper outlines the design of a pressure cell apparatus that is constructed of chemically resistant materials and is capable of generating drainage and imbibition capillary relationships at both positive and negative capillary pressures for sandy porous media containing organic liquids and surface-active solutes over a range of pH values. Its rapid response is caused primarily by a highly conductive capillary barrier and the continuous visual display of degree of saturation. Because of the high conductivity of the capillary barrier, bubbles form under it, limiting the cell to 40 h of use at a capillary pressure head of 150 cm H2O or 10 h at 200 cm H2O. This range is sufficient, however, to allow the generation of the five capillary pressure relationships necessary to characterize wett...

Data Reduction In Centrifuge Capillary Pressure Experiments

Abstract The centrifuge method is commonly used to determine the capillary pressure of a core. The data obtained from such an experiment is the average saturation of the core at different centrifugal speeds. It is necessary to back out the capillary pressure saturation relation based on our understanding of the equilibrium distribution of two fluids in porous media. The governing set of equations was first presented by Hassler and Brunner in 1945, and was accepted by the industry in general. With the use of ultra centrifugation in recent years, the possibility of water de-saturation at the exit end became a concern. While there was experimental evidence that de-saturatation can occur, some theoretical calculations indicated that this could only happen at much higher speed. The motivation to do the present study was to address this concern. While going over the original formulation it was noted that the radial dependence of capillary pressure was given by the authors without any discussion. According to their formulation, capillary pressure, which was the difference in pressure of two fluids, was taken to be defined even in a single fluid region. There was no reason given for taking this physically unrealistic definition. The pressure drop across the interface at the exit end was also taken to be zero, this was contrary to our expectation of interfacial behaviour in a capillary system. A re-formulation of the problem indicated that the error due to a wrong definition of capillary pressure was usually small, but that due to neglecting pressure drop at the exit end, must be evaluated by a separate experiment. This re-formulation also allowed us to derive a simple formula to estimate the centrifugal speed at which de-saturation of water at the exit end might occur. Introduction The measurement of capillary pressure saturation relation of a core by the centrifuge was proposed by Hassler and Brunner(1). They formulated the governing set of equations for the equilibrium distribution of two fluids under constant centrifugal acceleration and presented two approximation methods to calculate capillary pressure saturation relation from measured data. Since then there have been a large number of attempts to improve on these approximate solutions. Only four of these works(1–4) will be discussed in this study. Interested readers are referred to Ruth and Chen's(5) review article. The underlying theory as derived by Hassler and Brunner was accepted by all these authors. With the use of higher powered centrifuges some authors(6–10) started to be concerned with the possibility of de-saturation of water at the exit end. If this happened then the assumptions used by Hassler and Brunner might not be valid. In particular according to the original formulation the capillary pressure should be zero at the exit end, and it was interpreted(6–10) as equivalent to water saturation being 100% there. When Wunderlich(6) found that it could be less than 100 at high centrifuge speeds, he considered it as an indication that the boundary condition was being violated there.

Comparison of Galerkin-type discretization techniques for two-phase flow in heterogeneous porous media

A comparison of Standard Galerkin, Petrov-Galerkin, and Fully-Upwind Galerkin methods for the simulation of two-phase flow in heterogeneous porous media is presented. On the basis of the coupled pressure-saturation equations, a generalized formulation for all three finite element methods is derived and analysed. For flow in homogeneous media, the Petrov-Galerkin method gives excellent results. But this method fails miserably for problems with heterogeneous media. This is because it is not able to capture correctly processes that take place at interfaces when, for instance, the capillary pressure-saturation relationship after Brooks and Corey is assumed. The Fully-Upwind Galerkin method is superior to the Petrov-Galerkin approach because it is able to give correct results for flow in homogeneous and heterogeneous media for the two models of van Genuchten and Brooks-Corey. The widely used dp c dS w grad S w formulation which is correct for the homogeneous case cannot be used for heterogeneous media. Instead the straightforward approach of grad p c in combination with a chord-slope technique must be utilized.

Wave Propagation in Poroelastic Media Saturated by Two Fluids

A theory of wave propagation in isotropic poroelastic media saturated by two immiscible Newtonian fluids is presented. The macroscopic constitutive relations, and mass and momentum balance equations are obtained by volume averaging the microscale balance and constitutive equations and assuming small deformations. Momentum transfer terms are expressed in terms of intrinsic and relative permeabilities assuming the validity of Darcy’s law. The coefficients of macroscopic constitutive relations are expressed in terms of measurable quantities in a novel way. The theory demonstrates the existence of three compressional and one rotational wave. The third compressional wave is associated with the pressure difference between the fluid phase and dependent on the slope of the capillary pressure-saturation relation.

Residual gasoline saturation in unsaturated soil with and without organic matter

The goal of this study was to investigate the influence of one variable, natural organic matter, on residual gasoline saturation in sandy soils. Capillary pressure-saturation ( P c − S) relationships (air-gasoline) were determined for three physically-similar sandy soils, with different organic carbon contents (0.086%, 0.89% and 1.65%) and residual gasoline saturations were compared. Two initial moisture conditions, residual water saturation and air-dry, were evaluated. One soil type was packed to two different bulk densities. Visualization of the soils using cryo-scanning electron microscopy was performed to aid in better understanding the role of the organic matter in the soil. The results showed that soils with higher organic contents had higher residual gasoline saturations when starting with an initially air-dry soil. Increasing the bulk density of the same air-dried soil resulted in an increase in residual gasoline saturation. In the presence of a residual water saturation, however, residual gasoline saturations were virtually identical for the three soils and independent of bulk density; approximately 5–10 times lower than in soil that was initially air-dry. The presence of the residual water effectively coated the surface of the soil thereby reducing or eliminating gasoline/soil interactions. Some residual water may also be occupying very small pore spaces, making these locations inaccessible to the gasoline.

Wettability effects on scaling two-and three-fluid capillary pressure-saturation relations

Wettability effects on scaling two-and three-fluid capillary pressure-saturation relations

THE EFFECTIVE STRESS PRINCIPLE: INCREMENTAL OR FINITE FORM?

Different expressions of the effective stress principle can be found in the literature, in particular some are written in finite form and others in incremental form. For the purpose of the paper we take for granted that stress–strain relationships exist or can be obtained for the effective stress coming from both formulations. We investigate the consequences of the choice of particular finite or differential forms when they are introduced in a weak form of the linear momentum balance equation of two- of three-phase porous media for its numerical solution. For partially saturated geomaterials the importance of the capillary pressure–saturation relationship is pointed out.

Capillary pressure-saturation relations in porous media including the effect of wettability

In this work a functional relationship between capillary pressure and wetting phase saturation has been developed. Both the imbibition and drainage of a wetting phase liquid into a porous medium consisting of clean unconsolidated silica particles have been considered. In all, two bead packings, with average particle diameters of 120 μm and 360 μm, and three liquids—water, ethanol, and refrigerant-113—were studied. It was found that the Leverett function worked very well in describing the relation between capillary pressure and saturation for each liquid using both packings; however, it did not provide adequate correlation for all three liquids. The functional relationship presented here considers the dependence of capillary pressure upon the contact angle of the fluid-solid interface, and also conveys how this dependence varies with saturation. The inclusion of the contact angle dependence provides extension of the correlation to any wetting phase liquid of uniform properties.

Fractional wettability effects on two-and three-fluid capillary pressure-saturation relations

Studies of the relation between capillary pressure ( P c) and fluid saturation ( S) for porous media containing oil-water or air-oil-water, often assume that the medium is strongly water-wet. Natural porous media, however, are composed of a variety of mineral constituents; such media are typically composed of water- and oil-wet fractions. This study reports on two- and three-fluid P c- S data for media of different fractions of water- and oil-west sands. The oil-water capillary pressure, defined as the oil minus the water pressure, was measured during drainage (primary and main curves) as well as inhibition (main curve only) of water. A decrease in oil-water pressure was observed as the oil-wet fraction increased in two-fluid media. The pressure became negative during imbibition of water for relatively oil-wet media. The P c- S data could be adequately described by modifying the van Genuchten model for water retention. The observed differences between primary and main drainage curves were partly attributed to the effect of initial saturation. In three-fluid systems with fractional wettability, the observed dependency of capillary pressures on fluid saturations suggested that there was no continuous intermediate phase — even for a relatively low oil-wet fraction (25%). The oil-water and air-water capillary pressures decreased, at a particular water saturation, as the fraction of oil-wet sand increased. The water pressure is greater when water acts as the intermediate fluid than when it is the wetting fluid. The oil pressure, and hence the air-oil capillary pressure, was relatively insensitive to whether oil acted as wetting or intermediate fluid. There is a need to model three-fluid P c- S curves that account for different wetting and intermediate fluids.

Wettability Effects on Scaling Two- and Three-Fluid Capillary Pressure-Saturation Relations

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTWettability Effects on Scaling Two- and Three-Fluid Capillary Pressure-Saturation RelationsScott A. Bradford and Feike J. LeijCite this: Environ. Sci. Technol. 1995, 29, 6, 1446–1455Publication Date (Print):June 1, 1995Publication History Published online1 May 2002Published inissue 1 June 1995https://doi.org/10.1021/es00006a004RIGHTS & PERMISSIONSArticle Views241Altmetric-Citations38LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (3 MB) Get e-Alerts Get e-Alerts

Laboratory and model simulations of a LNAPL spill in a variably-saturated sand, 1. Laboratory experiment and image analysis techniques

A two-dimensional, multiphase flow experiment was conducted in the laboratory. The saturation distribution of a lighter than water non-aqueous-phase liquid (LNAPL) as it migrated through a variably-saturated sand medium was determined using image analysis techniques. The pressures in the water and LNAPL phases were measured using hydrophilic and hydrophobic porous cups connected to a series of pressure transducers and a data acquisition system. The LNAPL inflow and water outflow were also recorded. A series of capillary pressure-saturation experiments were conducted for each two-phase system. The capillary pressures recorded by the pressure transducers were used to calculate the pphase saturations based on a fully hysteretic capillary pressure-saturation algorithm. The static equilibrium capillary pressure-saturation relationships proved to be invalid immediately ahead of the LNAPL front. The capillary pressure-saturation relationship appeared to be dynamic for short periods of time as the LNAPL front arrived at each transducer location. The presence of an entrapped air phase as the LNAPL migrated through the unsaturated zone clearly affected the migration of the LNAPL and the maximum LNAPL saturation reached in the sand medium.

Laboratory measurement of capillary pressure-saturation relationships in a rock fracture : S. Reitsma & B.H. Kueper, Water Resources Research, 30(4), 1994, pp 865–878

Laboratory measurement of capillary pressure-saturation relationships in a rock fracture : S. Reitsma & B.H. Kueper, Water Resources Research, 30(4), 1994, pp 865–878

Effect of temperature and pore size on the hydraulic properties and flow of a hydrocarbon oil in the subsurface

Capillary pressure relationships in a porous medium determine the distribution of immiscible fluids under static conditions and can largely influence the movement of the fluids when the system is not at equilibrium. Theory predicts that for a given porous medium, the effect of different fluid properties or changes in temperature on capillary pressure are due to changes in interfacial tension and contact angle of the system. The capillary pressure-saturation curves measured here for hydrocarbon oil-water do not have a constant capillary pressure ratio with saturation when compared to the water-air system, and changes in ratio were found when comparing the water-air curves measured at different temperatures. Thus, the scaling theory based on interfacial tensions and contact angles does not adequately account for differences in capillary pressures due to different fluid pairs or temperatures. Also, the curves show the residual wetting and nonwetting phase saturations are greatly affected by temperature and sometimes by the fluid pair, which is not accounted for in the scaling theory and cannot be predicted. When the capillary pressure-saturation relationship is extended to the calculation of relative permeabilities and the prediction of fluid flow in the subsurface, the differences in measured and scaled capillary pressure curves lead to differences in the predicted flow rates and saturations of the immiscible fluids in the subsurface. Thus, care must be used when applying capillary pressure-saturation data from one fluid system to that of another, or when applying it to different conditions.

Micromodel studies of three-fluid porous media systems: pore scale processes relating to capillary pressure-saturation relationships : Soll, W E; Celia, M A; Wilson L J Water Resour ResV29, N9, Sept 1993, P2963–2974

Micromodel studies of three-fluid porous media systems: pore scale processes relating to capillary pressure-saturation relationships : Soll, W E; Celia, M A; Wilson L J Water Resour ResV29, N9, Sept 1993, P2963–2974

Effects of Depositional Facies and Diagenesis on Calculating Petrophysical Properties from Wireline Logs in Permian Carbonate Reservoirs of West Texas: ABSTRACT

The complex interplay between depositional facies and diagenesis in carbonate rocks presents numerous problems for calculating petrophysical properties from wireline logs. If carbonate reservoirs are divided into flow units of similar depositional and diagenetic textures, empirical equations that apply specifically to that geologically identified flow unit can be developed to accurately measure porosity and water saturation. In Guadalupian and Leonardian reservoirs, carbonate mudstones deposited in subtidal marine settings are predominantly dolomite, although they contain some shale. The shale in these rocks can be detected with gamma-ray logs and empirical equations for calculation of porosity from log must include a gamma-ray component to compensate for the presence of shale. Because porosity in these rocks is dominantly intercrystalline, capillary pressure characteristics are predictable and saturations can be calculated with the Archie equation. Subtidal carbonate packstones and grainstones are composed of dolomite, anhydrite, and gypsum. The matrix acoustic transit times of these three minerals are similar, and acoustic logs are the best tool for measuring porosity. Neutron logs are the least accurate porosity tools if gypsum is present. Photo-electric density logs can distinguish gypsum from anhydrite. Because porosity in these rocks is dominantly interparticle and/or moldic, dual porosity cementation exponent corrections are neededmore » to calculate saturations with the Archie equation, and capillary pressure saturation relationships are variable. Carbonates deposited in tidal-flat environments are generally composed of dolomite, sulfate minerals, and quartz silt, requiring a full suite of open-hole logs to make reliable porosity measurements. Diagenesis influences reservoir mineralogy and pore types. A common style of burial diagenesis in Guadalupian and Leonardian reservoirs is hydration of anhydrite to gypsum and leaching of sulfate cement and dolomite matrix.« less

A modified percolation approach to simulating three-fluid capillary pressure-saturation relationships

A computational model was developed for simulating capillary pressure-saturation relationships for porous media systems containing two or three mobile fluids. The model is based on describing fluid displacement on a pore-by-pore basis over a large number of pores to produce bulk saturations in the medium. The computational approach utilizes percolation and network theories to describe fluid movement within the pore space. Percolation theory calls for a set of displacement rules to determine the movement of the fluids under capillary-driven transport. A comprehensive set of rules appropriate for either two-fluid or three-fluid systems is described. These rules account for a variety of processes affecting displacement, such as wetting films, hysteresis, trapping of fluids, and gravity. The model is shown to reproduce the basic characteristics of a two-fluid capillary pressure-saturation curve, and model predictions are shown to agree with both two- and three-fluid experimental data.

Effect of heterogeneity on the drainage capillary pressure-saturation relation : Ferrand, L A; Celia, M A Water Resour ResV28, N3, March 1992, P859–870

Effect of heterogeneity on the drainage capillary pressure-saturation relation : Ferrand, L A; Celia, M A Water Resour ResV28, N3, March 1992, P859–870

Effect of interfacial forces on two-phase capillary pressure-saturation relationships : Demond, A H; Roberts, P V Water Resour ResV27, N3, March 1991, P423–427

Effect of interfacial forces on two-phase capillary pressure-saturation relationships : Demond, A H; Roberts, P V Water Resour ResV27, N3, March 1991, P423–427