Induced polarization response of porous media with metallic particles — Part 6: The case of metals and semimetals

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. E97-E110 ◽  
Author(s):  
André Revil ◽  
Deqiang Mao ◽  
Zhenlu Shao ◽  
Michael F. Sleevi ◽  
Deming Wang
Keyword(s):  
Relaxation Time ◽  
Tap Water ◽  
Core Sample ◽  
Induced Polarization ◽  
Copper Plate ◽  
Secondary Source ◽  
Water Conductivity ◽  
Metallic Particles ◽  
Two Parameters ◽  
Polarization Spectra

We collected spectral induced polarization spectra with clean sand mixed with metallic particles (either silver, graphite, copper, steel, magnetite, or pyrite particles). The initial pore water conductivity was either 1500 or [Formula: see text] depending on the experiments (25°C, NaCl). For each of the 15 experiments, we used a narrow and unimodal grain size distribution for the metallic particles. The resulting polarization spectra display clear polarization peaks in the phase and can be fitted with a Cole-Cole complex conductivity model. In addition to this, the chargeability scales with the volume content of the metallic particles in a way that is consistent with the theory of disseminated metallic particles in a weakly polarizable background. Similarly, the phase scales with the content of the metallic particles in a predictable way. The Cole-Cole relaxation time shows a rough dependence with the mean particle size. The trend between these two parameters can be used to determine an apparent diffusion coefficient for the charge carriers responsible for the polarization. Finally, we conducted a laboratory sandbox experiment in which we put a copper plate in tap water-saturated sand. We use an approach based on self-potential tomography and compactness to invert the secondary source current density from the secondary voltages associated with time-domain induced polarization. With this approach, we localized the copper plate and determined a value for the relaxation time that is consistent with the laboratory core sample experiments.

Induced polarization response of porous media with metallic particles — Part 5: Influence of the background polarization

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. E77-E96 ◽  
Author(s):  
André Revil ◽  
Michael F. Sleevi ◽  
Deqiang Mao
Keyword(s):  
Porous Materials ◽  
Tap Water ◽  
Current Model ◽  
Clay Content ◽  
Peak Frequency ◽  
Exchange Capacity ◽  
Induced Polarization ◽  
Data Sets ◽  
Phase Lag ◽  
Polarization Spectra

Very often, ore bodies are found in altered porous materials that are rich in clay minerals. These altered rocks are in turn characterized by a relatively high normalized chargeability (product of the chargeability by the high frequency conductivity) or electrical quadrature conductivity with respect to clay-free materials. We have performed 36 experiments in which dispersed pyrite grains were mixed with a background host material composed of some pore water (NaCl, [Formula: see text] at 25°C or tap water), Na-exchanged bentonite, and silica grains. The induced polarization spectra were obtained in the frequency range of 1 mHz to 45 kHz at room temperature ([Formula: see text]). The spectra of the background porous materials alone (i.e., without pyrite) were also measured. The normalized chargeability and the quadrature conductivity of the sand-clay mixtures are consistent with available theoretical relationships. These new data complete previous data sets showing a clear relationship among the normalized chargeability, quadrature conductivity, surface conductivity, and cation exchange capacity. Bentonite is characterized by very high quadrature and surface conductivities. The normalized chargeability and the quadrature conductivity of the sand-clay mixtures (no pyrite) increase with the clay content. In the presence of pyrite, the chargeability and the phase lag depend primarily on the volume content of pyrite in a predictable way. The Cole-Cole exponent, characterizing the particle size distribution of the pyrite grains, is independent of the clay content. Still, in the presence of pyrite, the magnitude of the phase peak and the phase peak frequency depend on the clay content in a way that is not explained by the current model. We have observed that the Cole-Cole relaxation time, in the presence of pyrite, is inversely proportional to the conductivity of the background material.

Induced polarization response of porous media with metallic particles — Part 3: A new approach to time-domain induced polarization tomography

Geophysics ◽  
2016 ◽  
Vol 81 (4) ◽  
pp. D345-D357 ◽  
Author(s):  
Deqiang Mao ◽  
André Revil
Keyword(s):  
Current Density ◽  
Time Domain ◽  
Induced Polarization ◽  
Charge Carriers ◽  
Secondary Source ◽  
Metallic Particles ◽  
Secondary Voltage ◽  
Source Current ◽  
Self Potential ◽  
Source Current Density

The secondary voltage associated with time-domain induced polarization data of disseminated metallic particles (such as pyrite and magnetite) in a porous material can be treated as a transient self-potential problem. This self-potential field is associated with the generation of a secondary-source current density. This source current density is proportional to the gradient of the chemical potentials of the [Formula: see text]- and [Formula: see text]-charge carriers in the metallic particles or ionic charge carriers in the pore water including in the electrical double layer coating the surface of the metallic grains. This new way to treat the secondary voltages offers two advantages with respect to the classical approach. The first is a gain in terms of acquisition time. Indeed, the target can be illuminated with a few primary current sources, all the other electrodes being used simultaneously to record the secondary voltage distribution. The second advantage is with respect to the inversion of the obtained data. Indeed, the secondary (source) current is linearly related to the secondary voltage. Therefore, the inverse problem of inverting the secondary voltages is linear with respect to the source current density, and the inversion can be done in a single iteration. Several iterations are, however, required to compact the source current density distribution, still obtaining a tomogram much faster than inverting the apparent chargeability data using the classical Gauss-Newton approach. We have performed a sandbox experiment with pyrite grains locally mixed to sand at a specific location in the sandbox to demonstrate these new concepts. A method initially developed for self-potential tomography is applied to the inversion of the secondary voltages in terms of source current distribution. The final result compares favorably with the classical inversion of the time-domain induced polarization data in terms of chargeability, but it is much faster to perform.

scholarly journals Induced polarization response of porous media with metallic particles — Part 8: Influence of temperature and salinity

Geophysics ◽  
2018 ◽  
Vol 83 (6) ◽  
pp. E435-E456 ◽  
Author(s):  
André Revil ◽  
Antoine Coperey ◽  
Deqiang Mao ◽  
Feras Abdulsamad ◽  
Ahmad Ghorbani ◽  
...  
Keyword(s):  
Activation Energy ◽  
Background Electrolyte ◽  
Element Model ◽  
Induced Polarization ◽  
Arrhenius Law ◽  
Water Conductivity ◽  
Dc Conductivities ◽  
Influence Of Temperature ◽  
Metallic Particles ◽  
C 50

We have investigated the influence of temperature and salinity upon the spectral induced polarization of 10 samples including rocks with their mineralization (galena, chalcopyrite) plus sand mixed with semiconductors such as magnetite grains, graphite, and pyrite cubes of two different sizes. Measurements are made in a temperature-controlled bath with a high-precision impedance meter and using NaCl solutions. We cover the temperature range 5°C−50°C and the frequency range [Formula: see text] to 45 kHz. For one large pyrite cube, we also investigated six salinities from 0.1 to [Formula: see text] (at 25°C, NaCl) and three salinities for graphite. The spectra are fitted with a Cole-Cole complex parametric conductivity model for which we provide a physical meaning to the four Cole-Cole parameters. As expected, the Cole-Cole exponent and the chargeability are independent of the temperature and salinity. The instantaneous and steady state (direct current [DC]) conductivities depend on the salinity and temperature. This temperature dependence can be fitted with an Arrhenius law (combining the Stokes-Einstein and Vogel-Fulcher-Tammann equations) with an activation energy in the range of [Formula: see text]. This activation energy is the same as for the bulk pore-water conductivity demonstrating the control by the background electrolyte of these quantities, as expected. The instantaneous and DC conductivities depend on the salinity in a predictable way. The Cole-Cole relaxation time decreases with the temperature and decreases with the salinity. This behavior can be modeled with an Arrhenius law with an apparent activation energy of [Formula: see text]. A finite-element model is used further to analyze the mechanisms of polarization, and it can reproduce the temperature and salinity dependencies observed in the laboratory.

A new approach to fitting induced-polarization spectra

Geophysics ◽  
2008 ◽  
Vol 73 (6) ◽  
pp. F235-F245 ◽  
Author(s):  
Sven Nordsiek ◽  
Andreas Weller
Keyword(s):  
Grain Size ◽  
Relaxation Time ◽  
Time Distribution ◽  
Induced Polarization ◽  
Model Parameters ◽  
Mass Percentage ◽  
Relaxation Time Distribution ◽  
Best Fitting ◽  
Cole Model ◽  
Polarization Spectra

Best fitting of induced-polarization (IP) spectra by different models of Cole-Cole type evidences discrepancies in the resulting model parameters. The time constant determined from the same data could vary in magnitude over several decades. This effect, which makes an evaluation of the results of different models nearly impossible, is demonstrated by induced polarization measurements in the frequency range between [Formula: see text] and [Formula: see text] on thirteen mixtures of quartz sand and slag grains. The samples differ in size and the amount of the slag grains. Parameters describing the IP spectra are derived by fitting models of the Cole-Cole type to the measured data. The fitting quality of the generalized Cole-Cole model, the standard Cole-Cole model, and the Cole-Davidson model is investigated. The parameters derived from these models are compared and correlated with mass percentage and grain size of the slag particles. An alternative fittingapproach is introduced, using the decomposition of observed IP spectra into a variety of Debye spectra. Four integrating parameters are derived and correlated with parameters of the slag-sand mixtures and Cole-Cole parameters, respectively. The alternative approach generally enables a better fitting of measured spectra compared with Cole-Cole type models. It proves to be more flexible and stable, even for complicated phase spectra that cannot be fitted by single Cole-Cole type models. The integrating parameters are well correlated with characterizing parameters of the slag-sand mixtures. The total chargeability well indicates the mass percentage of slag grains, and the mean relaxation time is related to the grain size. The relaxation time distribution can be displayed by cumulative normalized chargeability versus relaxation time, similar to granulation curves. Anologous to the latter, a nonuniformity parameter characterizes the width of the relaxation time distribution.

Induced polarization and pore radius — A discussion

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. D519-D526 ◽  
Author(s):  
Andreas Weller ◽  
Zeyu Zhang ◽  
Lee Slater ◽  
Sabine Kruschwitz ◽  
Matthias Halisch
Keyword(s):  
Diffusion Coefficient ◽  
Relaxation Time ◽  
Diffusion Coefficients ◽  
Pore Radius ◽  
Mercury Porosimetry ◽  
Induced Polarization ◽  
Reliable Estimate ◽  
Characteristic Relaxation Time ◽  
A Value ◽  
Apparent Diffusion

Permeability estimation from induced polarization (IP) measurements is based on a fundamental premise that the characteristic relaxation time [Formula: see text] is related to the effective hydraulic radius [Formula: see text] controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We have examined the link between a widely used single estimate of [Formula: see text] and [Formula: see text] for an extensive database of sandstone samples, in which mercury porosimetry data confirm that [Formula: see text] is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of one or two distinct representative diffusion coefficients but instead demonstrates strong evidence for six orders of magnitude of variation in an apparent diffusion coefficient that is well-correlated with [Formula: see text] and the specific surface area per unit pore volume [Formula: see text]. Two scenarios can explain our findings: (1) the length scale defined by [Formula: see text] is not equal to [Formula: see text] and is likely much longer due to the control of pore-surface roughness or (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g., silica and clays) making up the rock. In either case, the estimation of [Formula: see text] (and hence permeability) is inherently uncertain from a single characteristic IP relaxation time as considered in this study.

scholarly journals Estimation of the permeability of hydrocarbon reservoir samples using induced polarization and nuclear magnetic resonance methods

Geophysics ◽  
2019 ◽  
Vol 84 (2) ◽  
pp. MR73-MR84 ◽  
Author(s):  
Fatemeh Razavirad ◽  
Myriam Schmutz ◽  
Andrew Binley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Mechanistic Model ◽  
Transverse Relaxation Time ◽  
Induced Polarization ◽  
Permeability Model ◽  
Transverse Relaxation ◽  
Hydrocarbon Reservoir ◽  
Nuclear Magnetic

We have evaluated several published models using induced polarization (IP) and nuclear magnetic resonance (NMR) measurements for the estimation of permeability of hydrocarbon reservoir samples. IP and NMR measurements were made on 30 samples (clean sands and sandstones) from a Persian Gulf hydrocarbon reservoir. We assessed the applicability of a mechanistic IP-permeability model and an empirical IP-permeability model recently proposed. The mechanistic model results in a broader range of permeability estimates than those measured for sand samples, whereas the empirical model tends to overestimate the permeability of the samples that we tested. We also evaluated an NMR permeability prediction model that is based on porosity [Formula: see text] and the mean of the log transverse relaxation time ([Formula: see text]). This model provides reasonable permeability estimations for the clean sandstones that we tested but relies on calibrated parameters. We also examined an IP-NMR permeability model, which is based on the peak of the transverse relaxation time distribution, [Formula: see text] and the formation factor. This model consistently underestimates the permeability of the samples tested. We also evaluated a new model. This model estimates the permeability using the arithmetic mean of log transverse NMR relaxation time ([Formula: see text]) and diffusion coefficient of the pore fluid. Using this model, we improved estimates of permeability for sandstones and sand samples. This permeability model may offer a practical solution for geophysically derived estimates of permeability in the field, although testing on a larger database of clean granular materials is needed.

scholarly journals Induced polarization response of porous media with metallic particles — Part 7: Detection and quantification of buried slag heaps

Geophysics ◽  
2018 ◽  
Vol 83 (5) ◽  
pp. E277-E291 ◽  
Author(s):  
Youzheng Qi ◽  
Abdellahi Soueid Ahmed ◽  
André Revil ◽  
Ahmad Ghorbani ◽  
Feras Abdulsamad ◽  
...  
Keyword(s):  
Metal Content ◽  
Induced Polarization ◽  
Ore Deposits ◽  
Magnetic Method ◽  
Complex Conductivity ◽  
Metallic Particles ◽  
Polarization Response ◽  
Slag Heap ◽  
Detection And Quantification ◽  
Metallurgical Activities

With the progress of metallurgical activities, more and more dumped slag heaps emerge as valuable deposits to feed the growing need for metal resources. Detecting, quantifying, and reextracting metals from these slags may complement the prospection of new ore deposits. However, the spatial delineation of the slag heap cannot easily be obtained from the resistivity distribution alone (determined either with galvanometric or with induction-based methods). Although the magnetic method can detect slag heaps, it fails to make an estimation of the quantity of metal present in the slag. Alternatively, the induced polarization (IP) method can be used to fulfill this goal. The complex conductivity responses of slag samples from a slag heap in France are obtained in the laboratory. These data are used to assess the grade of the slag, which is close to 8%. Then, a least-squares 3D IP inversion is used to get the subsurface chargeability distribution delimiting the slag heap in the ground. From the linear relationship determined between the chargeability and the volumetric metal content or the volumetric slag content, the metallic volume of the slag heaps can be directly determined. This approach is used at the site of Saint-Vincent sur L'Isle, Dordogne (France), where it allows characterizing the shape of a slag heap and quantifying the total cumulative metal content of the investigated area.

Electrical properties of iron-sand columns: Implications for induced polarization investigation and performance monitoring of iron-wall barriers

Geophysics ◽  
2005 ◽  
Vol 70 (4) ◽  
pp. G87-G94 ◽  
Author(s):  
Lee D. Slater ◽  
Jaeyoung Choi ◽  
Yuxin Wu
Keyword(s):  
Relaxation Time ◽  
Surface Area ◽  
Performance Monitoring ◽  
Electrical Response ◽  
Induced Polarization ◽  
Iron Hydroxides ◽  
Interfacial Chemistry ◽  
Reactive Iron ◽  
Volume Formula ◽  
And Performance

We investigate the electrical response (0.1–1000 Hz) of reactive iron barriers by making measurements on zero valent iron ([Formula: see text])-sand columns under the following conditions: (1) variable [Formula: see text] surface area (0.1–100% by volume [Formula: see text] under constant electrolyte chemistry; (2) variable electrolyte activity (0.01–1 mol/liter), valence (mono trivalent), and pH under constant [Formula: see text]-sand composition; and (3) forced precipitation of iron hydroxides and iron carbonates on the [Formula: see text] surface. We model the measurements in terms of conduction magnitude, polarization magnitude, and polarization relaxation time. Our key findings are: (a) Polarization magnitude exhibits a linear relation to the surface area of [Formula: see text], whereas conduction magnitude is only weakly dependent on the [Formula: see text] concentration below 30% by volume [Formula: see text]. (b) Polarization magnitude shows a power law relation to electrolyte activity, with exponents decreasing from 0.9 for monovalent solutions to 0.7 for trivalent solutions. (c) The relaxation time parameter depends on activity and valence in a manner that is partly consistent with the variation in double layer thickness predicted from theory. (d) pH exerts minor control on the electrical parameters. (e) Polarization magnitude and relaxation time both increase as a result of precipitation induced on the surface of [Formula: see text]. Our results show that induced polarization parameters systematically change in response to changes in the [Formula: see text]-electrolyte interfacial chemistry.

Phosphate removal from source separated urine by electrocoagulation using iron plate electrodes

2009 ◽  
Vol 60 (11) ◽  
pp. 2929-2938 ◽  
Author(s):  
Xiang-yong Zheng ◽  
Hai-Nan Kong ◽  
De-yi Wu ◽  
Chong Wang ◽  
Yan Li ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Current Density ◽  
High Current Density ◽  
Tap Water ◽  
Complete Removal ◽  
Phosphate Removal ◽  
Electrolysis Time ◽  
Two Parameters ◽  
Hydrolysis Of ◽  
P Removal

The aim of this study was to investigate the effects of current density, gap between electrodes, urine dosage, dilution and hydrolysis on phosphate removal from human urine by electrocoagulation technique using iron as electrodes. It was shown that, although a high current density and a long electrolysis time favored the removal of phosphate, an appropriate value for these two parameters can be obtained by taking into account the consumption of energy and iron in addition to P removal. In this study, current density 40 mA/cm2 and electrolysis time 20 min were shown to be optimal for 1.0 L pure urine to achieve nearly a complete removal (98%) efficiency of phosphate under the conditions of electrode area 160 cm2, the stirring speed 150 rpm, and the gap between electrodes 5 mm. Increase of gap between electrodes had little effect on phosphate removal, although it increased the energy consumption dramatically. The use of a high urine dosage reduced the efficiency of phosphate removal but increased the amount of removed phosphate. When pure urine was diluted with tap water, use of a higher tap water proportion for dilution expedited the electrolysis to achieve a nearly complete removal of phosphate in solution, but dilution caused the increase in energy consumption. It was also revealed that the hydrolysis of urine prior to electrocoagulation treatment impeded phosphate removal.

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