ANALOGY BETWEEN DIFFUSION AND ELECTRICAL CONDUCTIVITY IN POROUS ROCKS

1951 ◽  
Vol 62 (6) ◽  
pp. 559 ◽  
Author(s):  
L. J. KLINKENBERG
Keyword(s):  
Electrical Conductivity ◽  
Porous Rocks

2D pore-scale simulation of wide-band electromagnetic dispersion of saturated rocks

Geophysics ◽  
2007 ◽  
Vol 72 (3) ◽  
pp. F97-F110 ◽  
Author(s):  
Emmanuel Toumelin ◽  
Carlos Torres-Verdín
Keyword(s):  
Electrical Conductivity ◽  
Dielectric Permittivity ◽  
Electric Fields ◽  
Electromagnetic Property ◽  
Wide Band ◽  
Geometrical Parameters ◽  
Pore Scale ◽  
Porous Rocks ◽  
Pore Connectivity ◽  
Scale Properties

Effective medium theories (EMTs) are invoked routinely to interpret multifrequency dispersions of dielectric permittivity and electrical conductivity of saturated rocks. However, EMTs exhibit limitations that substantially restrict their validity for petrophysical interpretation. For instance, pore connectivity is of significant interest in the study of subsurface reservoirs, but no existing EMT includes it as an explicit property in the analysis of kilohertz- to gigahertz-range dielectric measurements. We introduce a new approach to quantify the effects of pore geometry and connectivity on the kilohertz-gigahertz frequency dispersion of dielectric permittivity and electrical conductivity of clay-free porous rocks. This approach is based on the numerical solution of the internal electric fields within submicron-resolution pore maps constructed with grain and rock pixels. The discrepancy between the internal fields and electrical currents calculated for ahomogeneous scatterer and those calculated for a given pore map is minimized to yield the effective electrical conductivity and dielectric constant for that pore map. This minimization is performed independently for each frequency and is verified to agree implicitly with Kramers-Kronig's causality relationships. We show that EMTs only predict an average dispersion for given microscopic geometrical parameters (e.g., porosity, pore eccentricity), whereas individual realizations honoring the same parameters are associated with dispersion about average values predicted by EMTs. Unlike any EMT prediction, we show that pore connectivity plays a major role in both the shape and amplitude of wide-band electromagnetic property dispersions. The simulation procedure introduced in this paper provides a systematic method to assess the sensitivity of a multitude of pore-scale properties on the macroscopic wide-band dielectric dispersion of saturated rocks.

scholarly journals Effect of the water–steam phase transition on the electrical conductivity of porous rocks

Geothermics ◽  
2010 ◽  
Vol 39 (1) ◽  
pp. 106-114 ◽  
Author(s):  
Harald Milsch ◽  
Líney H. Kristinsdóttir ◽  
Erik Spangenberg ◽  
David Bruhn ◽  
Ólafur G. Flóvenz
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
Porous Rocks ◽  
Water Steam

Removing Substrate Background in TEM Microanalysis

1974 ◽  
Vol 32 ◽  
pp. 568-569
Author(s):  
John C. Russ ◽  
Nicholas C. Barbi
Keyword(s):  
Electrical Conductivity ◽  
Rapid Growth ◽  
Organic Film ◽  
Absolute Concentration ◽  
Background Signal ◽  
X Ray ◽  
Elemental Concentrations ◽  
Transmission Electron ◽  
Electron Microscopes ◽  
The Continuum

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.

Macromolecular structures of biological specimens are not obscured by controlled osmium impregnation

1983 ◽  
Vol 41 ◽  
pp. 606-607
Author(s):  
Klaus-Ruediger Peters ◽  
Samuel A. Green
Keyword(s):  
Thin Films ◽  
Electrical Conductivity ◽  
Critical Point ◽  
Metal Films ◽  
High Magnification ◽  
Osmium Impregnation ◽  
Instrumental Resolution ◽  
20 Nm ◽  
Continuous Metal

High magnification imaging of macromolecules on metal coated biological specimens is limited only by wet preparation procedures since recently obtained instrumental resolution allows visualization of topographic structures as smal l as 1-2 nm. Details of such dimensions may be visualized if continuous metal films with a thickness of 2 nm or less are applied. Such thin films give sufficient contrast in TEM as well as in SEM (SE-I image mode). The requisite increase in electrical conductivity for SEM of biological specimens is achieved through the use of ligand mediated wet osmiuum impregnation of the specimen before critical point (CP) drying. A commonly used ligand is thiocarbohvdrazide (TCH), first introduced to TEM for en block staining of lipids and glvcomacromolecules with osmium black. Now TCH is also used for SEM. However, after ligand mediated osinification nonspecific osmium black precipitates were often found obscuring surface details with large diffuse aggregates or with dense particular deposits, 2-20 nm in size. Thus, only low magnification work was considered possible after TCH appl ication.

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