Relating electrical conduction of alluvial sediments to textural properties and pore‐fluid conductivity

Abstract

Electrical conductivity of alluvial sediments depends on litho‐textural properties, fluid saturation and porewater conductivity. Therefore, for hydrostratigraphic applications of direct current resistivity methods in porous sedimentary aquifers, it can be useful to characterize the prevailing mechanisms of electrical conduction (electrolytic or shale conduction) according to the litho‐textural properties and to the porewater characteristics. An experimental device and a measurement protocol were developed and applied to collect data on eight samples of alluvial sediments from the Po plain (Northern Italy), characterized by different grain‐size distribution, and fully saturated with porewater of variable conductivity. The bulk electrical conductivities obtained with the laboratory tests were interpreted with a classical two‐component model, which requires the identification of the intrinsic conductivity of clay particles and the effective porosity for each sample, and with a three‐component model. The latter is based on the two endmember mechanisms, surface and electrolytic conduction, but takes into account also the interaction between dissolved ions in the pores and the fluid‐grain interface. The experimental data and their interpretation with the phenomenological models show that the volumetric ratio between coarse and fine grains is a simple but effective parameter to determine the electrical behaviour of clastic hydrofacies at the scale of the representative elementary volume.

Estimating geohydraulic parameters, protective strength, and corrosivity of hydrogeological units: a case study of ALSCON, Ikot Abasi, southern Nigeria

“…This clearly indicates that in the southern region of the study area, the hydrological units are protected from being exposed to interaction with the brackish water for borehole depths greater than 40 m due to hydrogeological formation divide. However, the conductivity of water increases (the resistivity decreases) toward the north due to divides between formations and geological formations in the study area (Mauro et al 2014). …”

Geoelectrohydraulic parameters of shallow sandy aquifer in Itu, Akwa Ibom State (Nigeria) using geoelectric and hydrogeological measurements

“…Archie found that the bulk electrical resistivity (q b ) is related to pore-water resistivity (q w ) as shown in Eq. (1) for a fully saturated and clay-free formation (Keller and Frischknecht, 1966;Mauro et al, 2014). The formation factor (F) represents a macroscopic property of rock/soil and can be expressed, in its simplest form in Eq.…”

A combined use of Archie and van Genuchten models for predicting hydraulic conductivity of unsaturated pyroclastic soils

“…However, Archie's law does not take into account surface conduction, which is more and more significant as the amount of clay minerals increases. Anyway, even when this law is modified to consider surface conduction (Clavier et al, 1984;Mele et al, 2014;Waxman and Smits, 1968), it is only valid for a single conducting phase that partially saturates a non-conducting matrix. Recently, a generalization of Archie's law to n-conducting phases has been proposed by Glover (2010), who also provides a summary of the most common mixing models for electrical conductivity in porous media.…”