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Water Saturation (water + saturation)

Distribution by Scientific Domains

Earth and Environmental Science	46%
Engineering	38%

Selected Abstracts

INVESTIGATION OF ELASTIC INVERSION ATTRIBUTES USING THE EXPANSIBLE CLAY MODEL FOR WATER SATURATION

JOURNAL OF PETROLEUM GEOLOGY, Issue 2 2009
J. O. Ugbo
Quantitative X-ray diffraction has been used to characterize water saturation levels in complex shaly sand reservoirs (i.e. shaly sands with infrequent carbonates and minor proportions of iron-rich minerals such as pyrite and siderite). The results led to the design of a total expansible clay model for water saturation, which is similar in form to the Dual Water model except that the excess effect of the clay minerals has been accounted for by a volume-conductivity relationship, rather than one of the usual volume-porosity translations, effectively reducing the uncertainties in estimating water saturation. Given the ambiguities associated with predicting these petrophysical properties from data on rock properties, such as mineralogy, an investigation of the relationship of estimated water saturation based on the total expansible clay model to independently determined rock properties was undertaken using well log inversion and forward modelling techniques. The results show that there is consistency in the relationship between water saturation estimates made from the total expansible clay model and known elastic parameters such as primary and shear-wave sonic velocity (Vp, Vs), bulk density (,b) and impedance (I), when the Raymer-Gardner-Hunt model is used. Use of the Raymer-Gardner-Hunt model to reconstruct the required rock-physics relationship avoids the classic limitation of the more advanced Gassman model, which assumes that the dry shear modulus is equivalent to the wet shear modulus (,dry=,wet). The present work raises further questions on the application of the Voigt-Reuss-Hill (VRH) limits, or the Hashin Shtrikman bounds for averaging the effective shear modulus of the dry matrix in complex shaly sand reservoirs, where a two-mineral matrix is normally assumed. The study shows the inapplicability of the VRH or Hashin-Shtrikman averaging techniques but provides a minor adjustment to the averaging that solves the problems faced in reconstructing the relationships between directly measured elastic properties and derived petrophysical properties for this type of reservoir rock. [source]

Effect of degree of fluid saturation on transport coefficients in disturbed soils

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2004
A. Tuli
Summary To improve the predictive capability of transport models in soils we need experimental data that improve their understanding of properties at the scale of pores, including the effect of degree of fluid saturation. All transport occurs in the same soil pore space, so that one may intuitively expect a link between the different transport coefficients and key geometrical characteristics of the pores such as tortuosity and connectivity, and pore-size distribution. To understand the combined effects of pore geometry and pore-size distribution better, we measured the effect of degree of water saturation on hydraulic conductivity and bulk soil electrical conductivity, and of degree of air saturation on air conductivity and gaseous diffusion for a fine sand and a sandy loam soil. To all measured data were fitted a general transport model that includes both pore geometry and pore-size distribution parameters. The results show that both pore geometry and pore-size distribution determine the functional relations between degree of saturation, hydraulic conductivity and air conductivity. The control of pore size on convective transport is more for soils with a wider pore-size distribution. However, the relative contribution of pore-size distribution is much larger for the unsaturated hydraulic conductivity than for gaseous phase transport. For the other transport coefficients, their saturation dependency could be described solely by the pore-geometry term. The contribution of the latter to transport was much larger for transport in the air phase than in the water phase, supporting the view that connectivity dominates gaseous transport. Although the relation between effective fluid saturation and all four relative transport coefficients for the sand could be described by a single functional relation, the presence of a universal relationship between fluid saturation and transport for all soils is doubtful. [source]

Lithology and hydrocarbon mapping from multicomponent seismic data

GEOPHYSICAL PROSPECTING, Issue 2 2010
Hüseyin Özdemir
ABSTRACT Elastic rock properties can be estimated from prestack seismic data using amplitude variation with offset analysis. P-wave, S-wave and density ,reflectivities', or contrasts, can be inverted from angle-band stacks. The ,reflectivities' are then inverted to absolute acoustic impedance, shear impedance and density. These rock properties can be used to map reservoir parameters through all stages of field development and production. When P-wave contrast is small, or gas clouds obscure reservoir zones, multicomponent ocean-bottom recording of converted-waves (P to S or Ps) data provides reliable mapping of reservoir boundaries. Angle-band stacks of multicomponent P-wave (Pz) and Ps data can also be inverted jointly. In this paper Aki-Richards equations are used without simplifications to invert angle-band stacks to ,reflectivities'. This enables the use of reflection seismic data beyond 30° of incident angles compared to the conventional amplitude variation with offset analysis. It, in turn, provides better shear impedance and density estimates. An important input to amplitude variation with offset analysis is the Vs/Vp ratio. Conventional methods use a constant or a time-varying Vs/Vp model. Here, a time- and space-varying model is used during the computation of the ,reflectivities'. The Vs/Vp model is generated using well log data and picked horizons. For multicomponent data applications, the latter model can also be generated from processing Vs/Vp models and available well data. Reservoir rock properties such as ,,, ,,, Poisson's ratio and bulk modulus can be computed from acoustic impedance, shear impedance and density for pore fill and lithology identification. , and , are the Lamé constants and , is density. These estimations can also be used for a more efficient log property mapping. Vp/Vs ratio or Poisson's ratio, ,, and weighted stacks, such as the one computed from ,, and ,/,, are good gas/oil and oil/water contact indicators, i.e., pore fill indicators, while ,, mainly indicates lithology. ,, is also affected by pressure changes. Results from a multicomponent data set are used to illustrate mapping of gas, oil and water saturation and lithology in a Tertiary sand/shale setting. Whilst initial log crossplot analysis suggested that pore fill discrimination may be possible, the inversion was not successful in revealing fluid effects. However, rock properties computed from acoustic impedance, shear impedance and density estimates provided good lithology indicators; pore fill identification was less successful. Neural network analysis using computed rock properties provided good indication of sand/shale distribution away from the existing wells and complemented the results depicted from individual rock property inversions. [source]

Groundwater fluctuations and footslope ferricrete soils in the humid tropical zone of southern Cameroon

HYDROLOGICAL PROCESSES, Issue 16 2005
Emile Temgoua
Abstract This paper discusses the relationship between the differentiation of ferruginous accumulations and the variable water saturation of footslope soil patterns. An analysis of the slope morphology of a typical hill in the forest zone of southern Cameroon and a seasonal survey of the levels of groundwaters, springs and rivers were considered in relation to the petrology of different soil patterns. The study site is a tabular hillock whose slopes present a progressive development from steep to gentle slopes. The variable residence time of water within the soil, creating an alternation of reducing and oxidizing conditions, affects soil chemistry, structure and lateral extension of the soil patterns. The ferruginous soil patterns, being formed on the footslopes, gradually increase in extent with decreasing slope angle and the relative rise of the groundwater level. The steep footslopes, where groundwater has a shorter residence time, show a soft mottled clay pattern, restricted to the bottom part of the slope. The moderate footslopes exhibit a deep permanent and a temporary perched groundwater table. The latter, with its regular capillary fringe, contributes to more reducing conditions within isolated domains in the soil patterns, and thus to the alternation with oxidizing conditions, generating a continuous hard soil pattern (massive carapace). The more gently dipping footslopes exhibit groundwater levels near the surface and also a significant amplitude of groundwater fluctuation. Iron, previously accumulated in moderate footslope patterns, is reduced, remobilized, and leached. The soil patterns formed develop into a variegated carapace, more extended along the slope, containing less iron, but nevertheless more hardened, due to the important fluctuations of the groundwater table. These patterns are limited to the zone of groundwater fluctuation and deteriorate as the water fluctuation zone recedes. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Soil frost effects on soil water and runoff dynamics along a boreal transect: 2.

HYDROLOGICAL PROCESSES, Issue 6 2001
Simulations
Abstract A physically based SVAT-model was tested with soil and snow physical measurements, as well as runoff data from an 8600 m2 catchment in northern Sweden in order to quantify the influence of soil frost on spring snowmelt runoff in a moderately sloped, boreal forest. The model was run as an array of connected profiles cascading to the brook. For three winter seasons (1995,98) it was able to predict the onset and total accumulation of the runoff with satisfactory accuracy. Surface runoff was identified as only a minor fraction of the total runoff occurring during short periods in connection with ice blocking of the water-conducting pores. Little surface runoff, though, does not mean that soil frost is unimportant for spring runoff. Simulations without frost routines systematically underestimated the total accumulated runoff. The possibility of major frost effects appearing in response to specific combinations of weather conditions were also tested. Different scenarios of critical initial conditions for the winter, e.g. high water saturation and delayed snow accumulation leading to an increased frost penetration, were tested. These showed that under special circumstances there is potential for increased spring runoff due to soil frost. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Numerical simulation of two-dimensional transient water driven non-Newtonian fluid flow in porous media

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2002
Zuojin Zhu
Abstract Numerical simulation of two-dimensional transient water driven non-Newtonian fluid flow in porous media has been performed. The hyperbolic non-Newtonian fluid model was used to describe the characteristics of non-Newtonian fluid flow. Governing equations were first approximated by implicit finite difference, and then solved by a stabilized bi-conjugate gradient (Bi-CGSTAB) approach. A comparison of the numerical results for the case of water driven Newtonian fluid was made to validate the numerical method. For water driven Newtonian fluid flow, it was found that the numerical results are satisfactorily consistent with those obtained by commercial software VIP which is the abbreviation of vector implicit procedure for numerical simulation of Newtonian fluid flow in porous media. The maximum deviation for average pressure is less than 1.5 per cent; the distribution of water saturation is almost the same as that obtained by VIP. For water driven non-Newtonian fluid flow in porous media, it was found that the factor of pressure gradient of the non-Newtonian fluid has significant effects on the process of oil recovery. The correction of numerical simulation based on the global mass balance plays an important role in oil reservoir simulation. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Numerical simulation of thermal,hydraulic characteristics in a proton exchange membrane fuel cell

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 5 2003
Y.M. Ferng
Abstract The thermal,hydraulic characteristics of a proton exchange membrane fuel cell (PEMFC) are numerically simulated by a simplified two-phase, multi-component flow model. This model consists of continuity, momentum, energy and concentration equations, and appropriate equations to consider the varying flow properties of the gas,liquid two-phase region in a PEMFC. This gas,liquid two-phase characteristic is not considered in most of the previous simulation works. The calculated thermal,hydraulic phenomena of a PEMFC are reasonably presented in this paper, which include the distributions of flow vector, temperature, oxygen concentration, liquid water saturation, and current density, etc. Coupled with the electrochemical reaction equations, current flow model can predict the cell voltage vs current density curves (i.e. performance curves), which are validated by the single-cell tests. The predicted performance curves for a PEMFC agree well with the experimental data. In addition, the positive effect of temperature on the cell performance is also precisely captured by this model. The model presented herein is essentially developed from the thermal,hydraulic point of view and can be considered as a stepping-stone towards a full complete PEMFC simulation model that can help the optima design for the PEMFC and the enhancement of cell efficiency. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Deformation, mass transfer and mineral reactions in an eclogite facies shear zone in a polymetamorphic metapelite (Monte Rosa nappe, western Alps)

JOURNAL OF METAMORPHIC GEOLOGY, Issue 2 2004
L. M. Keller
Abstract This study analyses the mineralogical and chemical transformations associated with an Alpine shear zone in polymetamorphic metapelites from the Monte Rosa nappe in the upper Val Loranco (N-Italy). In the shear zone, the pre-Alpine assemblage plagioclase + biotite + kyanite is replaced by the assemblage garnet + phengite + paragonite at eclogite facies conditions of about 650 °C at 12.5 kbar. Outside the shear zone, only minute progress of the same metamorphic reaction was attained during the Alpine metamorphic overprint and the pre-Alpine mineral assemblage is largely preserved. Textures of incomplete reaction, such as garnet rims at former grain contacts between pre-existing plagioclase and biotite, are preserved in the country rocks of the shear zone. Reaction textures and phase relations indicate that the Alpine metamorphic overprint occurred under largely anhydrous conditions in low strain domains. In contrast, the mineralogical changes and phase equilibrium diagrams indicate water saturation within the Alpine shear zones. Shear zone formation occurred at approximately constant volume but was associated with substantial gains in silica and losses in aluminium and potassium. Changes in mineral modes associated with chemical alteration and progressive deformation indicate that plagioclase, biotite and kyanite were not only consumed in the course of the garnet-and phengite-producing reactions, but were also dissolved ,congruently' during shear zone formation. A large fraction of the silica liberated by plagioclase, biotite and kyanite dissolution was immediately re-precipitated to form quartz, but the dissolved aluminium- and potassium-bearing species appear to have been stable in solution and were removed via the pore fluid. The reaction causes the localization of deformation by producing fine-grained white mica, which forms a mechanically weak aggregate. [source]

INVESTIGATION OF ELASTIC INVERSION ATTRIBUTES USING THE EXPANSIBLE CLAY MODEL FOR WATER SATURATION

Seasonal records of climatic change in annually laminated tufas: short review and future prospects,

JOURNAL OF QUATERNARY SCIENCE, Issue 5 2005
J. E. Andrews
Abstract Many Recent and fossil freshwater tufa stromatolites contain millimetre-scale, alternating laminae of dense micrite and more porous or sparry crystalline calcites. These alternating laminae have been interpreted to represent seasonally controlled differences in the biotic activity of microbes, and/or seasonally controlled changes in the rate of calcification. Either way, couplets of these microbially mediated alternating calcified laminae are generally agreed to represent annual seasonality. Combined stable isotope (,18O and ,13C) and trace element (Mg, Sr, Ba) geochemistry from Recent tufa stromatolites show that seasonal climatic information is available from these calcites. Variability in ,18O (and in one case Mg concentration) has been shown to be controlled primarily by stream temperature change, usually driven by solar insolation. In arid climates, seasonal evaporation can also cause ,18O enrichment by at least 1,. Variability in ,13C results potentially from: (1) seasonal change in plant uptake of 12C-enriched CO2; (2) seasonal change in degassing of 12C-enriched CO2 in the aquifer system; and (3) precipitation of calcite along the aquifer or river flow path, a process that increases ,13C of dissolved inorganic carbon (DIC) in the remaining water. Mechanisms 2 and 3 are linked because calcite precipitates in aquifers where degassing occurs, e.g. air pockets. The latter mechanism for ,13C enrichment has also been shown to cause sympathetic variation between trace element/Ca ratios and ,13C because trace elements with partition coefficients much greater than 1 (e.g. Sr, Ba) remain preferentially in solution. Since degassing in air pockets will be enhanced during decreased recharge when water saturation of the aquifer is lowest, sympathetic variation in trace element/Ca ratios and ,13C is a possible index of recharge and therefore precipitation intensity. High-resolution geochemical data from well-dated tufa stromatolites have great potential for Quaternary palaeoclimate reconstructions, possibly allowing recovery of annual seasonal climatic information including water temperature variation and change in rainfall intensity. However, careful consideration of diagenetic effects, particularly aggrading neomorphism, needs to be the next step. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Corrosion of coating materials in oxidizing and hydrogen chloride containing atmospheres

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2002
S.C. Cha
The boiler tubes in waste incinerator plants and power plants are mainly corrosive strained. This paper presents the corrosion behaviour of various coating materials in two corrosive atmospheres at 500°C. In a first test, Ni-based materials applied by High Velocity Oxygen Fuel Flame (HVOF)-spraying and Atmospheric Plasma Spraying (APS) as well as Cr-based materials obtained by diffusion coating process are tested in oxidizing atmosphere with water saturation. The results of the corrosion test in this H2O-O2 -N2 -atmosphere show that NiCr applied by HVOF is less oxidized than that applied by APS-coating, whereas NiCrBSi coating by APS shows higher resistance than that applied by HVOF-spraying. The diffusion coating of Cr/Si is better than that of pure Cr. In a second test, metallic Mo and W-based materials applied by thermal spraying are tested to verify their corrosion resistance in HCl-H2O-O2 -N2 -atmosphere. It is shown that pure Mo applied by APS on 13 CrMo 44 and WCrNi sprayed on 15 Mo 3 by HVOF as well as on 13 CrMo 44 show relatively high corrosion resistance, whereas Mo sprayed by APS on 15 Mo 3 is not resistant. Both tungsten-cobalt-chromium mixtures show extremely high oxidation rates. Base materials in both tests were the standard boiler tube materials 15 Mo 3 and 13 CrMo 44. But even the low corrosion rates of the best materials in these tests are higher compared to those of materials already presented by Cha et al. in an earlier paper. Korrosion von Beschichtungswerkstoffen in oxidierenden und chlorwasser-stoffhaltigen Atmosphären Die Wärmetauscherrohre von Müllverbrennungsanlagen und Kraftwerken sind hauptsächlich korrosiv beansprucht. Die vorliegende Veröffentlichung stellt das Korrosionsverhalten von verschiedenen Beschichtungswerkstoffen in zwei korrosiven Atmosphären bei einer Temperatur von 500°C vor. Zuerst wurden die durch Hochgeschwindigkeitsflammspritzen (HVOF) und atmosphärisches Plasmaspritzen (APS) aufgetragenen Ni-Basiswerkstoffe und die diffusionsbeschichteten Cr-Basiswerkstoffe in oxidierender Atmosphäre mit Wassersättigung getestet. Die Ergebnisse der Korrosionsversuche in der H2O-O2 -N2 -Atmosphäre zeigen, dass NiCr (HVOF) resistenter ist als durch APS Beschichtung, wobei die Beschichtung mit NiCrBSi durch APS höhere Beständigkeit als die durch HVOF zeigt. Eine diffusionsbeschichtete Cr/Si-Schicht zeigt höhere Beständigkeit als eine reine Cr-Schicht. In einer zweiten Versuchsreihe wurden metallisches Mo und W-Basiswerkstoffe auf Korrosionsbeständigkeit in HCl-H2O-O2 -N2 -Atmosphäre untersucht. Dabei zeigt sich, dass die Proben mit Mo (APS) auf 13 CrMo 44, sowie WCrNi (HVOF) auf 15 Mo 3 und 13 CrMo 44 relativ hohe Korrosionsbeständigkeiten besitzen. Dagegen ist Mo (APS) auf 15 Mo 3 nicht beständig. Beide W-Co-Verbindungen zeigen extrem hohe Oxidationsraten. Als Basiswerkstoffe wurden die Standard Kesselrohr-Werkstoffe 15 Mo 3 und 13 CrMo 44 gewählt. Aber auch die niedrigsten Korrosionsraten der besten Werkstoffe in dieser Untersuchung sind höher als diejenigen der in einer früheren Arbeit von Cha et al. vorgestellten Werkstoffe. [source]

A parametric study of multi-phase and multi-species transport in the cathode of PEM fuel cells

INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 8 2008
Nada Zamel
Abstract In this study, a mathematical model is developed for the cathode of PEM fuel cells, including multi-phase and multi-species transport and electrochemical reaction under the isothermal and steady-state conditions. The conservation equations for mass, momentum, species and charge are solved using the commercial software COMSOL Multiphysics. The catalyst layer is modeled as a finite domain and assumed to be composed of a uniform distribution of supported catalyst, liquid water, electrolyte and void space. The Stefan,Maxwell equation is used to model the multi-species diffusion in the gas diffusion and catalyst layers. Owing to the low relative species' velocity, Darcy's law is used to describe the transport of gas and liquid phases in the gas diffusion and catalyst layers. A serpentine flow field is considered to distribute the oxidant over the active cathode electrode surface, with pressure loss in the flow direction along the channel. The dependency of the capillary pressure on the saturation is modeled using the Leverette function and the Brooks and Corey relation. A parametric study is carried out to investigate the effects of pressure drop in the flow channel, permeability, inlet relative humidity and shoulder/channel width ratio on the performance of the cell and the transport of liquid water. An inlet relative humidity of 90 and 80% leads to the highest performance in the cathode. Owing to liquid water evaporation, the relative humidity in the catalyst layer reaches 100% with an inlet relative humidity of 90 and 80%, resulting in a high electrolyte conductivity. The electrolyte conductivity plays a significant role in determining the overall performance up to a point. Further, the catalyst layer is found to be important in controlling the water concentration in the cell. The cross-flow phenomenon is shown to enhance the removal of liquid water from the cell. Moreover, a shoulder/channel width ratio of 1:2 is found to be an optimal ratio. A decrease in the shoulder/channel ratio results in an increase in performance and an increase in cross flow. Finally, the Leverette function leads to lower liquid water saturations in the backing and catalyst layers than the Brooks and Corey relation. The overall trend, however, is similar for both functions. Copyright © 2007 John Wiley & Sons, Ltd. [source]