Reply to comment by A. Revil and N. Linde on ‘Streaming potential dependence on water-content in Fontainebleau sand’

To cite this version:Damien Jougnot, Niklas Linde, A. Revil, Claude Doussan. Derivation of soil-specific streaming potential electrical parameters from hydrodynamic characteristics of partially saturated soils. Vadose Zone Journal, 2012, 11 (1) AbstractWater movement in unsaturated soils gives rise to measurable electrical potential differences that are related to the flow direction and volumetric fluxes, as well as to the soil properties themselves. Laboratory and field data suggest that these so-called streaming potentials may be several orders of magnitudes larger than theoretical predictions that only consider the influence of the relative permeability and electrical conductivity on the self potential (SP) data. Recent work has partly improved predictions by considering how the volumetric excess charge in the pore space scales with the inverse of water saturation. We present a new theoretical approach that uses the flux-averaged excess charge, not the volumetric excess charge, to predict streaming potentials. We present relationships for how this effective excess charge varies with water saturation for typical soil properties using either the water retention or the relative permeability function. We find large differences between soil types and the predictions based on the relative permeability function display the best agreement with field data. The new relationships better explain laboratory data than previous work and allow us to predict the recorded magnitudes of the streaming potentials following a rainfall event in sandy loam, whereas previous models predict three orders of magnitude too small values. We suggest that the strong signals in unsaturated media can be used to gain information about fluxes (including very small ones related to film flow), but also to constrain the relative permeability function, the water retention curve, and the relative electrical conductivity function.3

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“…The volume averaging approach of Linde et al (2007) (Eq. [10]) clearly underestimates

C_{EK}^{rel} (S_{normalw})

(see also the discussion in Allègre et al, 2011). The predicted

{\overset{true¯}{Q}}_{normalv}^{eff, rel} (S_{normale})

from the WR approach is at low saturations several orders of magnitude larger than the predictions of Linde et al (2007) [e.g.,

{\overset{true¯}{Q}}_{normalv}^{eff} (S_{normalw}^{normalr}) = 3.4 \times 10^{5} {\overset{true¯}{Q}}_{normalv} (S_{normalw}^{normalr})

].…”

Section: Resultsmentioning

confidence: 97%

Derivation of Soil‐Specific Streaming Potential Electrical Parameters from Hydrodynamic Characteristics of Partially Saturated Soils

Jougnot

Linde

Revil

et al. 2012

Vadose Zone Journal

192

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“…Recently, Allègre et al (2012) modelled both Richards' equation for hydrodynamics and Poisson's equation for electrical potential for unsaturated conditions, using a 1-D finite element method. They concluded, based on previous laboratory experiments (Allègre et al 2010(Allègre et al 2011, that the unsaturated electrokinetic coefficient should have a non-monotonous behaviour. Moreover, experimental results from periodic succession of drainage and imbibition cycles on sand suggested that the air-water interface that develops for unsaturated conditions gets polarized and therefore generates an electrical response (Allègre et al 2014).…”

Section: Effective Model Parametersmentioning

confidence: 98%

Dependence of shear wave seismoelectrics on soil textures: a numerical study in the vadose zone

Zyserman¹,

Monachesi

Jouniaux

2016

Geophys. J. Int.

Self Cite

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In this work, we study seismoelectric conversions generated in the vadose zone, when this region is traversed by a pure SH wave. We assume that the soil is a 1-D partially saturated lossy porous medium and we use the van Genuchten's constitutive model to describe the water saturation profile. Correspondingly, we extend Pride's formulation to deal with partially saturated media. In order to evaluate the influence of different soil textures we perform a numerical analysis considering, among other relevant properties, the electrokinetic coupling, coseismic responses and interface responses (IRs). We propose new analytical transfer functions for the electric and magnetic field as a function of the water saturation, modifying those of Bordes et al. and Garambois & Dietrich, respectively. Further, we introduce two substantially different saturation-dependent functions into the electrokinetic (EK) coupling linking the poroelastic and the electromagnetic wave equations. The numerical results show that the electric field IRs markedly depend on the soil texture and the chosen EK coupling model, and are several orders of magnitude stronger than the electric field coseismic ones. We also found that the IRs of the water table for the silty and clayey soils are stronger than those for the sandy soils, assuming a non-monotonous saturation dependence of the EK coupling, which takes into account the charged air-water interface. These IRs have been interpreted as the result of the jump in the viscous electric current density at the water table. The amplitude of the IR is obtained using a plane SH wave, neglecting both the spherical spreading and the restriction of its origin to the first Fresnel zone, effects that could lower the predicted values. However, we made an estimation of the expected electric field IR amplitudes detectable in the field by means of the analytical transfer functions, accounting for spherical spreading of the SH seismic waves. This prediction yields a value of 15 µV m −1 , which is compatible with reported values.

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“…Guichet et al [2003] measured the streaming potential during drainage under gas in a water-wet sandpack and reported a monotonic decrease in relative coupling coefficient ( Figure 1a); however, in similar experiments, Allègre et al [2010] obtained strongly nonmonotonic behavior, with the relative coupling coefficient increasing by some 2 orders of magnitude before decreasing with decreasing water saturation ( Figure 1b). Revil et al [2007] also reported a monotonic behavior of relative coupling coefficient in dolomite core samples, but, as pointed out by Allègre et al [2011], they calculated C r based on a value of C (S w = 1) that was extrapolated from the data obtained at partial saturation. When their data are rescaled to the value of C (S w = 1) reported by Revil and Cerepi [2004] for experiments on the same samples, C r again exhibits nonmonotonic behavior and exceeds the value at saturation (Figure 1a; compare open and closed triangles, noting the closed triangles plot against the right-hand axis).…”

Section: Introductionmentioning

confidence: 97%

“…[] also reported a monotonic behavior of relative coupling coefficient in dolomite core samples, but, as pointed out by Allègre et al . [], they calculated C r based on a value of C ( S w = 1) that was extrapolated from the data obtained at partial saturation. When their data are rescaled to the value of C ( S w = 1) reported by Revil and Cerepi [] for experiments on the same samples, C r again exhibits nonmonotonic behavior and exceeds the value at saturation (Figure a; compare open and closed triangles, noting the closed triangles plot against the right‐hand axis).…”

Section: Introductionmentioning

confidence: 99%

Streaming potential during drainage and imbibition

et al. 2017

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The rock pore space in many subsurface settings is saturated with water and one or more immiscible fluid phases. Examples include nonaqueous phase liquids (NAPLs) in contaminated aquifers, supercritical CO2 during sequestration in deep saline aquifers, the vadose zone, and hydrocarbon reservoirs. Self‐potential (SP) and seismoelectric (SE) methods have been proposed to monitor multiphase flow in such settings. However, to properly interpret and model these data requires an understanding of the saturation dependence of the streaming potential. This paper presents a methodology to determine the saturation dependence of the streaming potential coupling coefficient (C) and streaming current charge density (Qs) in unsteady state drainage and imbibition experiments and applies the method to published experimental data. Unsteady state experiments do not yield representative values of C and Qs (or other transport properties such as relative permeability and electrical conductivity) at partial saturation (Sw) because Sw within the sample is not uniform. An interpretation method is required to determine the saturation dependence of C and Qs within a representative elementary volume with uniform saturation. The proposed method makes no assumptions about the pore space geometry. Application of the method to published experimental data from two natural sandstone samples shows that C exhibits hysteresis between drainage and imbibition, can exhibit significant nonmonotonic variations with saturation, is nonzero at the irreducible water saturation, and can exceed the value observed at Sw = 1. Moreover, Qs increases with decreasing Sw but is not given by 1/Sw as is often assumed. The variation in Qs with Sw is very similar for a given sample and a given drainage or imbibition process, and the difference between samples is less than the difference between drainage and imbibition. The results presented here can be used to help interpret SP and SE measurements obtained in partially saturated subsurface settings.

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Reply to comment by A. Revil and N. Linde on ‘Streaming potential dependence on water-content in Fontainebleau sand’

Cited by 14 publications

References 19 publications

Derivation of Soil‐Specific Streaming Potential Electrical Parameters from Hydrodynamic Characteristics of Partially Saturated Soils

Derivation of Soil‐Specific Streaming Potential Electrical Parameters from Hydrodynamic Characteristics of Partially Saturated Soils

Dependence of shear wave seismoelectrics on soil textures: a numerical study in the vadose zone

Streaming potential during drainage and imbibition

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