Impedance of black shale from Munsterland 1 borehole: an anomalously good conductor?

Duba, A.; Huengest, E.; Nover, G.; Will, G.; Jödicke, H.

doi:10.1111/j.1365-246x.1988.tb02264.x

Cited by 67 publications

(31 citation statements)

References 19 publications

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“…Such hydrothermally driven events are well documented for the Karoo Basin (Duane and Brown, 1992;McDonald and Rozendaal, 1995) and its uranium deposits (Duane et al, 1989). The organic petrological data for sample A would support this hypothesis and is consistent with the observations of Duba et al (1988).…”

Section: Discussionsupporting

confidence: 79%

“…However, efficient electrical conduction in sample A could be achieved by interconnection of microscopic graphite films at the grain boundaries. This was the case for high electrical conductivities of black shales from the Münsterland-1 borehole where grain-boundary carbon was deposited during pyrolisis of organic carbon (Duba et al, 1988).…”

Section: Vitrinite Reflectance and Organic Petrographymentioning

confidence: 99%

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The Whitehill Formation a high conductivity marker horizon in the Karoo Basin

Branch

Ritter²,

Weckmann

et al. 2007

South African Journal of Geology

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Within the Inkaba yeAfrica project, magnetotelluric (MT) data were acquired along three profiles across the Karoo Basin in South Africa. The entire Karoo Basin and its sedimentary sequences are intersected by a number of deep boreholes, which were drilled during exploration for coal, oil and uranium. One of the most consistent and prominent 2 features in the electrical conductivity images is a shallow, regionally continuous, subhorizontal band of high conductivity that seems to correlate with the Whitehill Formation. The Whitehill Formation in particular is known to be regionally persistent in composition and thickness and can be traced throughout the entire Karoo Basin. In the region of our experiments, the Whitehill Formation varies in thickness between 50 to 70 m and consists of pyritic black shales with up to 14 wt% carbonaceous matter. Rocks can exhibit high electrical conductivity if electronically conducting minerals, such as graphite, are interconnected. To study physical properties and the maturity of the carbon present in the Whitehill Formation, impedance spectroscopy and vitrinite reflectance were applied to core samples from the SA1/66 borehole, taken from this formation at a depth range between 2750 m and 2800 m. Vitrinite reflectance analysis of the pseudocoal and oil shale rocks indicates that most of the carbon is in the meta-anthracite maturity field, approaching, in one sample, the "graphite window". Impedance

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Section: Discussionsupporting

confidence: 79%

Section: Vitrinite Reflectance and Organic Petrographymentioning

confidence: 99%

The Whitehill Formation a high conductivity marker horizon in the Karoo Basin

Branch

Ritter²,

Weckmann

et al. 2007

South African Journal of Geology

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“…The resistivity is I am or less at 300øC. This value is similar to that reported by Duba et al [1988] for an untreated low-grade metamorphic black shale of the same origin. Thus our temperature treatment resulted in a resistivity reduction of The phase transformations for sample mue3 are shown in Figure 9b.…”

Section: Electrical Resistivity At High Temperaturesupporting

confidence: 77%

“…These highly conducting layers have stimulated a controversial discussion concerning their origin. Widely accepted theories refer to carbon [Duba et al, 1988 sometimes known to be associated with conductivity anomalies [Gaucher, 1983;dtdicke, 1985], which are detected mainly in the lower parts of these basins.…”

Section: Introductionmentioning

confidence: 99%

Role of sulfur and carbon in the electrical conductivity of the middle crust

Raab¹,

Hoth²,

Huenges³

et al. 1998

J. Geophys. Res.

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“…The electrical properties of rocks depend strongly on microstructural and thermodynamical parameters. For example, the chemistry and salinity of the saturating brine and the geometry of the void (cracks and pores) network are controlling parameters together with pressure and temperature (Duba et al, 1988). In the holes drilled in the upper part of the oceanic crust, the formation water in the vicinity of the borehole is supposed to be seawater (Mottl et al, 1983), and the influence of temperature and salinity on sodium chloride aqueous solutions is well known (Sen and Goode, 1992).…”

Section: Introductionmentioning

confidence: 99%

Electrical Conduction in Oceanic Dikes, Hole 504B

Revil¹,

Darot²,

Pézard³

et al. 1996

Proceedings of the Ocean Drilling Program, 148 Scientific Results

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Porosity, cation-exchange capacity (CEC), and electrical conductivity have been measured on 28 doleritic minicores from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) Hole 504B (Legs 137, 140, and 148). Conductivity experiments were performed under five different saturating-fluid salinities, at room temperature and pressure, and with a twoelectrode conducting cell. At 4 kHz, the porosity is related to the "intrinsic" formation factor by an inverse power law similar to Archie's formula F = a Φ" m with m = 0.94 and a = 16 for the fine-grained specimens. Such a low m value suggests a current conduction in cracks and microcracks present at mineral scale throughout the rock. The presence of clays as alteration products is reflected by the high values of CEC. As expected, Q v /F (where Q v is the CEC per unit pore volume) and the surface conductivity are well correlated. This point leads to an estimate of the surface tortuosity. The temperature dependence of the surface conductivity is extracted using data on DC electrical conductivity at different temperature. For temperature correction purposes, a linear temperature dependence appears to be a good estimate for this parameter.On the basis of these results, an equation was given that allows estimation of the porosity from resistivity measurements in Hole 504B. This equation was tested by comparing the predicted conductivity against the measured conductivity of a large set of samples.

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Impedance of black shale from Munsterland 1 borehole: an anomalously good conductor?

Cited by 67 publications

References 19 publications

The Whitehill Formation a high conductivity marker horizon in the Karoo Basin

The Whitehill Formation a high conductivity marker horizon in the Karoo Basin

Role of sulfur and carbon in the electrical conductivity of the middle crust

Electrical Conduction in Oceanic Dikes, Hole 504B

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