Analysis of electrical conduction in the grain consolidation model

Geophysics ◽  
1987 ◽  
Vol 52 (10) ◽  
pp. 1402-1411 ◽  
Author(s):  
Lawrence M. Schwartz ◽  
Stephen Kimminau
Keyword(s):  
Electrical Conductivity ◽  
Grain Growth ◽  
Pore Space ◽  
Formation Factor ◽  
Minimum Area ◽  
Simulation Techniques ◽  
Fluid Saturation ◽  
Diagenetic Processes ◽  
Consolidation Model ◽  
Spherical Grains

In the grain consolidation model the diagenetic processes of compaction and cementation are represented in terms of the growth of an array of originally spherical grains. Grain growth toward the nodes of the pore space leads to an electrical formation factor F(ϕ) that increases slowly as the porosity ϕ decreases. By contrast, grain growth toward the throats of the pore space leads to a rapidly increasing F(ϕ). In all the cases we have examined, the value of the percolation threshold, [Formula: see text] is less than 0.055. Network simulation techniques have been developed to calculate the electrical conductivity of the ordered versions of the grain consolidation model. We find that the minimum‐area approximation employed in our earlier work is generally quite satisfactory. The network techniques can also be used to model the effects of mixed pore‐space fluid saturation, with results that are physically reasonable although not necessarily in agreement with empirical rules regarding saturation.

Influence of Microgeometry on Membrane Potential of Shaly Sands

1990 ◽  
Vol 195 ◽  
Author(s):  
Pabitra N. Sen
Keyword(s):  
Electrical Conductivity ◽  
Membrane Potential ◽  
Pore Space ◽  
Geometrical Parameters ◽  
Formation Factor ◽  
Water Conductivity ◽  
Shaly Sand ◽  
Local Geology ◽  
Geometrical Factors

ABSTRACTThe microgeometry of the pore space influences the membrane potential Em. and theDC electrical conductivity σ of a shaly sand in a similar manner, independent of the details of the geometry: Em and σ being related via the conductivities of cations and σanions;σ=σcation + σ onion, and Em α σ cation/(σcation + σanion). This explicit relationship is used to investigate the role of the geometrical factors which influence both Em and σ in a related manner. The dependence of σ on the water conductivity σw can be well approximated with four geometrical parameters which can be obtained from the slopes and the interceptsof σ vs. σw curve at high and low salinities. We show that these geometrical factors appear in the expression for Em a well. These geometrical parameters (one of them is the formation factor) vary from rock to rock, and any trend in these parameters depend on the local geology.

Numerical estimation of electrical conductivity in saturated porous media with a 2-D lattice gas

Geophysics ◽  
2000 ◽  
Vol 65 (3) ◽  
pp. 766-772 ◽  
Author(s):  
Michel Küntz ◽  
Jean Claude Mareschal ◽  
Paul Lavallée
Keyword(s):  
Electrical Conductivity ◽  
Porous Media ◽  
Power Law ◽  
Lattice Gas ◽  
Effective Conductivity ◽  
Pore Space ◽  
Solid Matrix ◽  
Conductivity Ratio ◽  
Saturated Porous Media ◽  
Formation Factor

A 2-D lattice gas is used to calculate the effective electrical conductivity of saturated porous media as a function of porosity and conductivity ratio [Formula: see text] between the pore‐filling fluid and the solid matrix for various microscopic structures of the pore space. The way the solid phase is introduced allows the porosity ϕ to take any value between 0 and 1 and the geometry of the pore structure to be as complex as desired. The results are presented in terms of the formation factor [Formula: see text], with [Formula: see text] the effective conductivity of the saturated rock and [Formula: see text] the conductivity of the fluid. It is shown that the formation factor F as a function of the porosity ϕ follows a power law [Formula: see text], equivalent to the empirical Archie’s law. The exponent m varies with the microgeometry of the pore space and could therefore reflect the microstructure at the macroscopic scale. The prefactor a of the power law, however, is close to 1 regardless of the microstructure. For a given microgeometry of the pore space, the variation of the residual electrical conductivity of the solid matrix induced by a finite conductivity ratio [Formula: see text] does not significantly influence the variation of the effective conductivity of the fluid‐solid binary mixture unless the porosity is low.

scholarly journals Electrical conductivity and pore-space topology of Merapi Lavas: Implications for the degassing of porphyritic andesite magmas

2001 ◽  
Vol 28 (22) ◽  
pp. 4283-4286 ◽  
Author(s):  
Jean-Luc Le Pennec ◽  
Daniel Hermitte ◽  
Isya Dana ◽  
Philippe Pezard ◽  
Christian Coulon ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Pore Space ◽  
Space Topology

Rapid microwave synthesis of Cu2Se thermoelectric material with high conductivity

2021 ◽  
pp. 2151005
Author(s):  
Yongpeng Wang ◽  
Wenying Wang ◽  
Haoyu Zhao ◽  
Lin Bo ◽  
Lei Wang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Growth ◽  
Microwave Synthesis ◽  
Annealing Process ◽  
High Electrical Conductivity ◽  
Cooling Process ◽  
Slow Cooling ◽  
Te Material ◽  
Hot Pressing Sintering

In this study, the dense bulk Cu2Se thermoelectric (TE) materials were prepared by microwave melting and hot pressing sintering. The effects of different cooling processes on the microstructure and TE properties of Cu2Se were investigated. The results showed that the Cu2Se TE material prepared by microwave synthesis had high electrical conductivity, which was about 105 S⋅ m[Formula: see text]. The annealing process can lead to grain growth of Cu2Se and the formation of micropores in the Cu2Se, which deteriorated the thermal conductivity. The Cu2Se material prepared by the microwave melting and slow cooling process had the best TE performance, and the ZT value can reach 0.68 at 700 K.

scholarly journals Parameter Selection for the Evaluation of Compost Quality

Agronomy ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1567
Author(s):  
Haydee Peña ◽  
Heysa Mendoza ◽  
Fernando Diánez ◽  
Mila Santos
Keyword(s):  
Electrical Conductivity ◽  
Organic Matter ◽  
Pore Space ◽  
Linear Regression Analysis ◽  
Organic Matter Content ◽  
Principal Component ◽  
Primary Component ◽  
Matter Content ◽  
Germination Index ◽  
Soil Restoration

This work studies variables measured from the first phase of composting through the acquisition of the final product, with the goal of identifying those that are more strongly related to quality and are most useful for developing an index. The necessity to establish quality control procedures thus exists for the classification of raw materials in the same way as for the finished products. To accomplish this, three mixtures were prepared, with the goal of achieving a C/N ratio of 30 and a moisture content of 60%. The primary component of each mixture was: fruit processing waste (C1), sewage sludge from the food industry (C2), and the manufacturing waste of fried foods (C3). Temperatures were measured over 107 days, with the corresponding data fit to a logistical model where T °C ~ α / ((1 + exp (− (Time − β) / − γ))) + δ, with interaction compost * time being statistically significant (p < 0.001). This allowed for the temperatures, in keeping with health concerns, to be confirmed. Likewise, a linear regression analysis demonstrated the decomposition of organic matter at 0.82%/week. Statistically, the parameters, measured during the process, with the least variability were selected, which differed in the average contrasts: germination index (cucumber), electrical conductivity, and average moisture. A principal component analysis (PCA) and Spearman’s correlation analysis revealed the best Germination Index (GI) values for C1, due to lower electrical conductivity (EC) and bulk density (Bd) along with higher organic matter content (TOM). For its part, C2 induced a higher Relative emergence (RE) of the cucumber thanks to its higher content of total nitrogen (TN) and lower contribution of Cu, Zn and K. C3 showed a higher presence of salts, less favorable physical characteristics (>Bd and <TPS, total pore space) and higher content of Zn and Cu. Composting carried out with appropriate mixtures can offer high-quality products for use as fertiliser, in soil restoration, and as an alternative substrate to peat and virgin mountain soil.

Zum Kornwachstum beim reinen und dotierten polykristallinen Selen / Grain Growth of Pure and Doped Poly crystalline Selenium

1971 ◽  
Vol 26 (7) ◽  
pp. 1198-1201
Author(s):  
C. Weyrich
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Grain Growth ◽  
Annealing Time ◽  
High Purity ◽  
The Mean ◽  
Grain Surface ◽  
Polycrystalline Form ◽  
Grain Diameter

Abstract Grain Growth of Pure and Doped Poly crystalline Selenium Samples of vitreous high-purity selenium as well as vitreous chlorine-and thallium-doped selenium have been brought into the polycrystalline form by annealing. The dependence of grain size on annealing time tu was measured. In high-purity selenium and in chlorine-doped selenium the mean grain diameter increases essentially ~ tu1/2 , in thallium-doped selenium ~ tu1/2 , as is expected from the laws of grain growth. The proportionality between electrical conductivity and specific grain surface reported by other authors could not be verified.

Scaling of Transport Properties of Reservoir Material at Low Saturations of a Wetting Phase

1994 ◽  
Vol 367 ◽  
Author(s):  
Y. Carolina Araujo ◽  
Pedro G. Toledo ◽  
Hada Y. Gonzalez
Keyword(s):  
Electrical Conductivity ◽  
Porous Media ◽  
Transport Properties ◽  
Capillary Pressure ◽  
Power Law ◽  
Scaling Laws ◽  
Pore Space ◽  
Conductivity Data ◽  
Phase Saturation ◽  
Electrical Conductivity Data

AbstractTransport properties of natural porous media have been observed to obey scaling laws in the wetting phase saturation. Previous work relates power-law behavior at low wetting phase saturations, i.e., at high capillary pressures, to the thin-film physics of the wetting phase and the fractal character of the pore space of porous media. Here, we present recent combined porousplate capillary pressure and electrical conductivity data of Berea sandstone at low saturations that lend support to the scaling laws. Power law is interpreted in terms of the exponent m in the relation of surface forces and film thickness and the fractal dimension D of the interface between pore space and solid matrix. Simple determination of D from capillary pressure and m from electrical conductivity data can be used to rapidly determine wetting phase relative permeability and capillary dispersion coefficient at low wetting phase saturations.

Matrix Diffusion Measurements – Through Diffusion versus Electrical Conductivity Measurements

2000 ◽  
Vol 663 ◽  
Author(s):  
Y. Ohlsson ◽  
I. Neretnieks
Keyword(s):  
Electrical Conductivity ◽  
Pure Water ◽  
Effective Diffusivity ◽  
Surface Conductivity ◽  
Bulk Liquid ◽  
Matrix Diffusion ◽  
Conductivity Measurements ◽  
Formation Factor ◽  
Conductivity Method ◽  
Through Diffusion

ABSTRACTMatrix diffusion laboratory experiments in dense porous rock are generally very time consuming and one is limited to rather short diffusion lengths, as well as to a small amount of samples. The large heterogeneity of rock, on the other hand, demands a large quantity of samples that are large enough to exclude effects from e.g. increases in interconnected porosity compared to that of the pristine rock.Electrical conductivity measurements are very fast and larger samples can be used than is practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied.In this study traditional through diffusion experiments as well as electrical conductivity measurements are carried out on the same rock samples. The formation factor is determined by both methods, and the methods are compared and discussed.The surface conductivity is studied by exchanging the surface sites with Na+, Sr2+ and Cs+. After leaching out the free pore ions the surface conductivity is measured.With the electrical conductivity method the formation factor is determined directly, whereas it has to be calculated using the bulk liquid diffusion coefficient in the diffusion experiments. This causes some uncertainties in the comparison between the experiments. In estimating the bulk liquid diffusivity, the value for infinitely diluted solutions and in pure water environment is commonly used. The calculated formation factor may therefore be somewhat underestimated.

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