The Determination of Qv From Membrane Potential Measurements on Shaly Sands

Thomas, E.C.

doi:10.2118/5505-pa

Cited by 56 publications

(29 citation statements)

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“…1). The cation exchange capacity (CEC), which is the quantity of exchangeable cations on a negatively charged mineral surface, is not the same for these two clay minerals: For smectite the CEC is 0.8-1.5 meq/g (Ellis, 1987); for chlorite, 0.01 meq/g (Thomas, 1976). This could explain the difference in conductivity between the smectite/zeolite and the chlorite/epidote alteration zones.…”

Section: Electrical Conduction Mechanisms and Their Temperature Depenmentioning

confidence: 99%

Electrical conductivity and P-wave velocity in rock samples from high-temperature Icelandic geothermal fields

et al. 2010

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Section: Electrical Conduction Mechanisms and Their Temperature Depenmentioning

confidence: 99%

Electrical conductivity and P-wave velocity in rock samples from high-temperature Icelandic geothermal fields

et al. 2010

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“…However, interpretation is complicated by the presence of clay minerals. Clays consist essentially of alumino-silicate minerals, which have a deficit of charge due to (1) substitution of ions in the crystal structure by ions of different valence, and (2) acid/base reactions between surface silanol/aluminol groups and water [e.g., Thomas, 1976]. The "counterions" required to counterbalance this charge deficit are located in the so-called electrical double layer [Waxman and Srnits, 1968;Avena and De Pauli, 1996; and Janusz et al, 1997].…”

Section: Introductionmentioning

confidence: 99%

“…The Hanai-Bruggeman equation [Bruggeman, 1935;Hanai, 1960Hanai, , 1961BussJan, 1983] was developed using a self- (Table 1). For NaC1, 0.38, and for KC1, t(•+) (K +) --0.50 [e.g., Thomas, 1976]. To first approximation, the Hittorf transport numbers in the free electrolyte are independent of both salinity and temperature s and t•_) as [e.g., Thomas, 1976].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Electrical conductivity in shaly sands with geophysical applications

Revil¹,

Cathles²,

Losh³

et al. 1998

J. Geophys. Res.

403

419

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Abstract. We develop a new electrical conductivity equation based on Bussian's model and accounting for the different behavior of ions in the pore space. The tortuosity of the transport of anions is independent of the salinity and corresponds to the bulk tortuosity of the pore space which is given by the product of the electrical formation factor F and the porosity •p.For the cations, the situation is different. At high salinities, the dominant paths for the electromigration of the cations are located in the interconnected pore space, and the tortuosity for the transport of cations is therefore the bulk tortuosity. As the salinity decreases, the dominant paths for transport of the cations shift from the pore space to the mineral water interface and consequently are subject to different tortuosities. This shift occurs at salinities corresponding to ½ / t[+) ~ 1, where • is the ratio between the surface conductivity of the grains and the electrolyte conductivity, and t[+) is the Hittorf transport number for cations in the electrolyte. The electrical conductivity of granular porous media is determined as a function of pore fluid salinity, temperature, water and gas saturations, shale content, and porosity. The model provides a very good explanation for the variation of electrical conductivity with these parameters. Surface conduction at the mineral water interface is described with the Stem theory of the electrical double layer and is shown to be independent of the salinity in shaly sands above 10 -3 mol L -1 . The model is applied to in situ salinity determination in the Gulf Coast, and it provides realistic salinity profiles in agreement with sampled pore water. The results clearly demonstrate the applicability of the equations to well log interpretation of shaly sands.

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“…) is the mobility of the counterions responsible for surface electrical conduction in the vicinity of the pore water/mineral interface, b S (Na + , 25°C) = 0.51 Â 10 À8 m 2 s À1 V À1 [Revil et al, 1998], s S corresponds to surface conductivity, and t (+) is the fraction of electrical current carried in the free electrolyte by the cations, t (+) (Na + ) % 0.38 independent of both salinity and temperature [Thomas, 1976]. The cation exchange capacity of the clay fraction, CEC Sh , can be related to the cation exchange capacity of the whole sediment, CEC, and to the cation exchange capacity of each clay component (in the present case CEC(C) for chlorite and CEC(I) for illite, both being fairly well-constrained parameters, see Table 1) by…”

Section: Influence Of Salinity and Clay Contentmentioning

confidence: 99%

In situ mineralogy and permeability logs from downhole measurements: Application to a case study in chlorite‐coated sandstones

2003

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[1] Well-logging techniques provide continuous profiles of various in situ physical properties like the bulk density, the photoelectric effect, and the natural gamma radioactivity of geological formations. Our purpose is to use this information to determine a continuous profile of the mineralogy with depth. The well-log derived mineralogy is then combined with a petrophysical model to infer continuous permeability and saturation profiles in chlorite-bearing sandstone formations. Our mineralogical inversion algorithm combines a cluster analysis of the raw data and their inversion using the generalized nonlinear inverse method developed by Tarantola and Valette [1982]. A field case is treated concerning a borehole intersecting an alternation of sandstones and shales. The mineralogical logs we obtained are in very good agreement with the mineral proportions measured independently on core samples. Mineralogical profiles are combined with a specific textural model to derive a continuous profile of permeability. We found a very good agreement between this computed permeability log and independent core permeability measurements over 3 orders of magnitude.INDEX TERMS: 5114 Physical Properties of Rocks: Permeability and porosity; 5139 Physical Properties of Rocks: Transport properties; 5109 Physical Properties of Rocks: Magnetic and electrical properties; 1832 Hydrology: Groundwater transport; KEYWORDS: downhole measurement, permeability, mineralogy, electrical resistivity, sandstone, chlorite Citation: Rabaute, A., A. Revil, and E. Brosse, In situ mineralogy and permeability logs from downhole measurements: Application to a case study in chlorite-coated sandstones,

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The Determination of Qv From Membrane Potential Measurements on Shaly Sands

Cited by 56 publications

References 0 publications

Electrical conductivity and P-wave velocity in rock samples from high-temperature Icelandic geothermal fields

Electrical conductivity and P-wave velocity in rock samples from high-temperature Icelandic geothermal fields

Electrical conductivity in shaly sands with geophysical applications

In situ mineralogy and permeability logs from downhole measurements: Application to a case study in chlorite‐coated sandstones

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