Electrical Conduction in Oceanic Dikes, Hole 504B

Abstract

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.

Complex conductivity tensor of anisotropic hydrocarbon-bearing shales and mudrocks

“…The second additive term in this last equation corresponds to the surface conductivity σ S . Equation 6 is also very close to the equation proposed by Revil et al (1996) (their equation 15) for watersaturated doleritic core samples from the oceanic crust. A simple generalization of the above expression to anisotropic media yields the following expression for the in-phase conductivity tensor…”

“…Tortuosity in this case can also be related to the aspect ratio of grains, as discussed in Mandelson and Cohen (1982). Other published experimental works have report very high tortuosities; for instance Revil et al (1996) reported tortuosities in the range of 2-46 for doleritic core samples. Zhang and Scherer (2012, their Table 6) have report electrical tortuosities in the range 2-118 for tight shales.…”

Relationship between porosity, electrical conductivity, and cation exchange capacity in Barbados wedge sediments

“…Furthermore, model surface conductance is derived from measurements in NaCl solutions, and the influence of having a higher divalent cation content (40% of the total charge) in the boundary layers and/or interlayers is not known. An alternative explanation is to assume a high tortuosity for the network of conductive surfaces (Revil et al, 1996)…”

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

“…The results of Flóvenz et al (1985) for core samples from Icelandic geothermal wells, and of Pezard (1990) for basaltic cores from the Ocean Drilling Project support this conclusion. A thorough theoretical and experimental study on this subject has been undertaken by Revil et al (1996Revil et al ( , 2002 and Revil and Glover (1997).…”