A new concept in modeling the dielectric response of sandstones: Defining a wetted rock and bulk water system

Geophysics ◽  
1990 ◽  
Vol 55 (5) ◽  
pp. 586-594 ◽  
Author(s):  
Rosemary Knight ◽  
Anthony Endres
Keyword(s):  
Dielectric Response ◽  
Water Saturation ◽  
Water System ◽  
Theoretical Models ◽  
Bulk Water ◽  
Frequency Range ◽  
Poor Agreement ◽  
Text Data ◽  
Pronounced Increase ◽  
Saturation Region

Experimental data for the real part of the dielectric constant (K′) of three sandstone samples are considered as a function of the level of water saturation [Formula: see text] in the frequency range 60 kHz to 4 MHz. Existing theoretical models have previously shown poor agreement with K′ versus [Formula: see text] data for rock samples, undoubtedly due to the complexity involved in adequately accounting for geometrical and electrochemical effects. In analyzing the data presented here, we find a pronounced increase in K′ in the low saturation region which in all cases can be attributed to the establishment of geometrical and surface effects associated with the rock‐water interface. When this increase in K′ is accounted for by defining wetted matrix parameters, the data show excellent agreement with existing theoretical models.

scholarly journals The dielectric constant of sandstones, 60 kHz to 4 MHz

Geophysics ◽  
1987 ◽  
Vol 52 (5) ◽  
pp. 644-654 ◽  
Author(s):  
Rosemary J. Knight ◽  
Amos Nur
Keyword(s):  
Dielectric Constant ◽  
Surface Area ◽  
Dielectric Response ◽  
Water Saturation ◽  
Pore Space ◽  
Strong Dependence ◽  
Complex Impedance ◽  
Volume Ratio ◽  
Electrode Polarization ◽  
Frequency Range

Complex impedance data were collected for eight sandstones at various levels of water saturation [Formula: see text] in the frequency range of 5 Hz to 4 MHz. The measurements were made using a two‐electrode technique with platinum electrodes sputtered onto the flat faces of disk‐ shaped samples. Presentation of the data in the complex impedance plane shows clear separation of the response due to polarization at the sample‐electrode interface from the bulk sample response. Electrode polarization effects were limited to frequencies of less than 60 kHz, allowing us to study the dielectric constant κ′ of the sandstones in the frequency range of 60 kHz to 4 MHz. κ′ of all samples at all levels of saturation shows a clear power‐law dependence upon frequency. Comparing the data from the eight sandstones at [Formula: see text], the magnitude of the frequency dependence was found to be proportional to the surface area‐to‐volume ratio of the pore space of the sandstones. The surface area‐to‐volume ratio of the pore space of each sandstone was determined using a nitrogen gas adsorption technique and helium porosimetry. κ′ also exhibits a strong dependence on [Formula: see text]. κ′ increases rapidly with [Formula: see text] at low saturations, up to some critical saturation above which κ′ increases more gradually and linearly with [Formula: see text]. Using the surface area‐to‐volume ratios of the sandstones, the critical saturation in the dielectric response was found to correspond to water coverage of approximately 2 nm on the surface of the pore space. Our interpretation of the observed dependence of κ′ on both frequency and [Formula: see text] is that it is the ratio of surface water to bulk water in the pore space of a sandstone that controls the dielectric response through a Maxwell‐Wagner type of mechanism.

High Frequency Dielectric Response of the Ionic Liquid N-Methyl-N-ethylpyrrolidinium Dicyanamide

2007 ◽  
Vol 60 (1) ◽  
pp. 6 ◽  
Author(s):  
Simon Schrödle ◽  
Gary Annat ◽  
Douglas R. MacFarlane ◽  
Maria Forsyth ◽  
Richard Buchner ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Dielectric Loss ◽  
Dielectric Relaxation ◽  
High Frequency ◽  
Dielectric Response ◽  
Room Temperature ◽  
Room Temperature Ionic Liquid ◽  
Dielectric Relaxation Spectroscopy ◽  
Frequency Range ◽  
Fast Rotation

A study of the room-temperature ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide by dielectric relaxation spectroscopy over the frequency range 0.2 GHz ≤ ν ≤ 89 GHz has revealed that, in addition to the already known lower frequency processes, there is a broad featureless dielectric loss at higher frequencies. The latter is probably due to the translational (oscillatory) motions of the dipolar ions of the IL relative to each other, with additional contributions from their fast rotation.

Numerical Modeling of Multi-Frequency Complex Dielectric Permittivity Dispersion of Sedimentary Rocks

Geophysics ◽  
2021 ◽  
pp. 1-69
Author(s):  
Artur Posenato Garcia ◽  
Zoya Heidari
Keyword(s):  
Numerical Simulation ◽  
Dielectric Permittivity ◽  
Numerical Simulations ◽  
Dielectric Response ◽  
Water Saturation ◽  
Pore Scale ◽  
Simulation Results ◽  
Wet Rocks ◽  
Permittivity Measurements ◽  
The Impact

The dielectric response of rocks results from electric double layer (EDL), Maxwell-Wagner (MW), and dipolar polarizations. The EDL polarization is a function of solid-fluid interfaces, pore water, and pore geometry. MW and dipolar polarizations are functions of charge accumulation at the interface between materials with contrasting impedances and the volumetric concentration of its constituents, respectively. However, conventional interpretation of dielectric measurements only accounts for volumetric concentrations of rock components and their permittivities, not interfacial properties such as wettability. Numerical simulations of dielectric response of rocks provides an ideal framework to quantify the impact of wettability and water saturation ( Sw) on electric polarization mechanisms. Therefore, in this paper we introduce a numerical simulation method to compute pore-scale dielectric dispersion effects in the interval from 100 Hz to 1 GHz including impacts of pore structure, Sw, and wettability on permittivity measurements. We solve the quasi-electrostatic Maxwell's equations in three-dimensional (3D) pore-scale rock images in the frequency domain using the finite volume method. Then, we verify simulation results for a spherical material by comparing with the corresponding analytical solution. Additionally, we introduce a technique to incorporate α-polarization to the simulation and we verify it by comparing pore-scale simulation results to experimental measurements on a Berea sandstone sample. Finally, we quantify the impact of Sw and wettability on broadband dielectric permittivity measurements through pore-scale numerical simulations. The numerical simulation results show that mixed-wet rocks are more sensitive than water-wet rocks to changes in Sw at sub-MHz frequencies. Furthermore, permittivity and conductivity of mixed-wet rocks have weaker and stronger dispersive behaviors, respectively, when compared to water-wet rocks. Finally, numerical simulations indicate that conductivity of mixed-wet rocks can vary by three orders of magnitude from 100 Hz to 1 GHz. Therefore, Archie’s equation calibrated at the wrong frequency could lead to water saturation errors of 73%.

Bulk-Water System Enhances Security, Minimizes Disruption

Opflow ◽  
2010 ◽  
Vol 36 (2) ◽  
pp. 8-8
Author(s):  
David M. Hughes ◽  
Dave Ericsson
Keyword(s):  
Water System ◽  
Bulk Water

scholarly journals Legionella Diversity and Spatiotemporal Variation in the Occurrence of Opportunistic Pathogens within a Large Building Water System

Pathogens ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 567 ◽  
Author(s):  
Helen Y. Buse ◽  
Brian J. Morris ◽  
Vicente Gomez-Alvarez ◽  
Jeffrey G. Szabo ◽  
John S. Hall
Keyword(s):  
Water Quality ◽  
Water System ◽  
Bulk Water ◽  
Quality Parameters ◽  
Water Quality Parameters ◽  
Opportunistic Pathogens ◽  
Water Age ◽  
Large Building ◽  
Survival Mechanisms ◽  
Culture Positive

Understanding Legionella survival mechanisms within building water systems (BWSs) is challenging due to varying engineering, operational, and water quality characteristics unique to each system. This study aimed to evaluate Legionella, mycobacteria, and free-living amoebae occurrence within a BWS over 18–28 months at six locations differing in plumbing material and potable water age, quality, and usage. A total of 114 bulk water and 57 biofilm samples were analyzed. Legionella culturability fluctuated seasonally with most culture-positive samples being collected during the winter compared to the spring, summer, and fall months. Positive and negative correlations between Legionella and L. pneumophila occurrence and other physiochemical and microbial water quality parameters varied between location and sample types. Whole genome sequencing of 19 presumptive Legionella isolates, from four locations across three time points, identified nine isolates as L. pneumophila serogroup (sg) 1 sequence-type (ST) 1; three as L. pneumophila sg5 ST1950 and ST2037; six as L. feeleii; and one as Ochrobactrum. Results showed the presence of a diverse Legionella population with consistent and sporadic occurrence at four and two locations, respectively. Viewed collectively with similar studies, this information will enable a better understanding of the engineering, operational, and water quality parameters supporting Legionella growth within BWSs.

A physically based model for the electrical conductivity of partially saturated porous media

2020 ◽  
Vol 223 (2) ◽  
pp. 993-1006
Author(s):  
Luong Duy Thanh ◽  
Damien Jougnot ◽  
Phan Van Do ◽  
Nguyen Van Nghia A ◽  
Vu Phi Tuyen ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Porous Media ◽  
Fractal Dimension ◽  
Water Saturation ◽  
Theoretical Models ◽  
Fluid Composition ◽  
Physically Based Model ◽  
Partially Saturated ◽  
Proposed Model ◽  
Physically Based

SUMMARY In reservoir and environmental studies, the geological material characterization is often done by measuring its electrical conductivity. Its main interest is due to its sensitivity to physical properties of porous media (i.e. structure, water content, or fluid composition). Its quantitative use therefore depends on the efficiency of the theoretical models to link them. In this study, we develop a new physically based model that takes into account the surface conductivity for estimating electrical conductivity of porous media under partially saturated conditions. The proposed model is expressed in terms of electrical conductivity of the pore fluid, water saturation, critical water saturation and microstructural parameters such as the minimum and maximum pore/capillary radii, the pore fractal dimension, the tortuosity fractal dimension and the porosity. Factors influencing the electrical conductivity in porous media are also analysed. From the proposed model, we obtain an expression for the relative electrical conductivity that is consistent with other models in literature. The model predictions are successfully compared with published experimental data for different types of porous media. The new physically based model for electrical conductivity opens up new possibilities to characterize porous media under partially saturated conditions with geoelectrical and electromagnetic techniques.

Multilayer capacitors with bismuth copper tantalate dielectric fabricated in LTCC technology

2016 ◽  
Vol 33 (3) ◽  
pp. 118-123 ◽  
Author(s):  
Dorota Szwagierczak ◽  
Jan Kulawik ◽  
Beata Synkiewicz ◽  
Agata Skwarek
Keyword(s):  
Dielectric Properties ◽  
Grain Boundaries ◽  
Dielectric Response ◽  
Tape Casting ◽  
High Specific Capacitance ◽  
Frequency Range ◽  
Content Type ◽  
Temperature Range ◽  
New Material ◽  
Multilayer Capacitors

Purpose The work was aimed at preparation of green tapes based on a new material Bi2/3CuTa4O12, to achieve spontaneously formation of an internal barrier layer capacitor (IBLC), fabrication of multilayer elements using low temperature cofired ceramics (LTCC) technology and their characterization. Design/methodology/approach The study focused on tape casting, lamination and co-sintering procedures and dielectric properties of Bi2/3CuTa4O12 multilayer capacitors. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies of the ceramic elements were performed. Impedance spectroscopy was used for characterization of dielectric properties in the frequency range of 0.1 Hz to −2 MHz and in the temperature range from −55 to 400°C. DC conductivity was investigated in the temperature range 20 to 740°C. Findings SEM observations revealed a good compatibility of the applied commercial Pt paste with the ceramic layers. The EDS microanalysis showed a higher content of oxygen at grain boundaries. The dominant dielectric response, which was recorded in the low frequency range and at temperatures above 0°C, was attributed to grain boundaries. The dielectric response at low temperatures and/or high frequencies was related to grains. The fabricated multilayer capacitors based on Bi2/3CuTa4O12 exhibited a high specific capacitance. Originality/value A new material Bi2/3CuTa4O12 was applied for preparation of green ceramic tapes and utilized for fabrication of multilayer ceramic capacitors using the LTCC technology. This material belongs to the group of high permittivity nonferroelectric compounds with a complex perovskite structure of CaCu3Ti4O12, that causes the spontaneously formation of IBLCs.

scholarly journals Extraction of Aloesin from Aloe vera Rind Using Alternative Green Solvents: Process Optimization and Biological Activity Assessment

Biology ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 951
Author(s):  
Mikel Añibarro-Ortega ◽  
José Pinela ◽  
Ana Ćirić ◽  
Elsa Lopes ◽  
Adriana K. Molina ◽  
...  
Keyword(s):  
Aloe Vera ◽  
Water System ◽  
Thiobarbituric Acid ◽  
Theoretical Models ◽  
Extraction Process ◽  
Response Analysis ◽  
Green Solvents ◽  
Health Food ◽  
Alcohol Water ◽  
Bioactive Potential

Aloesin is an aromatic chromone with increasing applications in the cosmetic and health food industries. To optimize its extraction from the Aloe vera leaf rind, the independent variables time (10–210 min), temperature (25–95 °C) and organic solvent composition (0–100%, w/w) were combined in a central composite design coupled with response surface methodology. The solvents consisted of binary mixtures of water with ethanol, propylene glycol, or glycerol. The aloesin levels quantified in each extract were used as response for optimization. The theoretical models were fitted to the experimental data, statistically validated, and used to obtain the optimal extraction conditions. Then, a dose–response analysis of the solid/liquid ratio (S/L) was performed under the optimal conditions determined for each alcohol–water system and revealed that a linear improvement in extraction efficiency can be achieved by increasing the S/L ratio by up to 40 g/L. This analysis also allowed to experimentally validate the predictive models. Furthermore, the aloesin-rich extracts revealed antioxidant activity through thiobarbituric acid reactive substances (TBARS) formation inhibition, antimicrobial effects against bacterial and fungal strains, and no toxicity for PLP2 cells. Overall, this study provided optimal extraction conditions for the recovery of aloesin from Aloe vera rind through an eco-friendly extraction process and highlighted its bioactive potential.

scholarly journals Petrophysical Analysis of Well Logs for Asmari Reservoir in Abu Ghirab Oil Field, South Eastern Iraq

2020 ◽  
pp. 2979-2990
Author(s):  
Buraq Adnan Al-Baldawi
Keyword(s):  
Gamma Ray ◽  
Water Saturation ◽  
Bulk Water ◽  
Computer Processing ◽  
Oil Field ◽  
Well Logs ◽  
Asmari Formation ◽  
Petrophysical Properties ◽  
Resistivity Logs ◽  
Environmental Corrections

The present study includes the evaluation of petrophysical properties and lithological examination in two wells of Asmari Formation in Abu Ghirab oil field (AG-32 and AG-36), Missan governorate, southeastern Iraq. The petrophysical assessment was performed utilizing well logs information to characterize Asmari Formation. The well logs available, such as sonic, density, neutron, gamma ray, SP, and resistivity logs, were converted into computerized data using Neuralog programming. Using Interactive petrophysics software, the environmental corrections and reservoir parameters such as porosity, water saturation, hydrocarbon saturation, volume of bulk water, etc. were analyzed and interpreted. Lithological, mineralogical, and matrix recognition studies were performed using porosity combination cross plots. Petrophysical characteristics were determined and plotted as computer processing interpretation (CPI) using Interactive Petrophysics program. Based on petrophysical properties, Asmari Reservoir in Abu Ghirab oil field is classified into three sub formations: Jeribe/ Euphrates and Kirkuk group which is divided into two zones: upper Kirkuk zone, and Middle-Lower Kirkuk zone. Interpretation of well logs of Asmari Formation indicated a commercial Asmari Formation production with medium oil evidence in some ranges of the formation, especially in the upper Kirkuk zone at well X-1. However, well X-2, especially in the lower part of Jeribe/ Euphrates and Middle-Lower Kirkuk zone indicated low to medium oil evidence. Lithology of Asmari Formation demonstrated a range from massive dolomite in Jeribe/ Euphrates zone to limestone in upper Kirkuk zone and limestone and sandstone in middle-lower Kirkuk zone, whereas mineralogy of the reservoir showed calcite and dolomite with few amounts of anhydrite.

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