Saturation Dependence of the Streaming Potential Coefficient

Abstract

Observations of streaming potential for unsaturated conditions do not always show the same trend depending on the hydrodynamic conditions and because of a lake of coherency between the data processing procedures. We combine the data from three studies published in the literature, acquired during non-steady state drainage experiments, and apply the same processing steps. We model the hydrodynamic behaviour of these experiments to confirm that they experienced different flow dynamics. We argue that the raw SP data should not be corrected unless a clear drift of the electrodes stability is observed. The combined hydrodynamic behaviour and the streaming potential response show that (a) the observations of one of the experiment (exp #1) are associated to a limited range of water saturation (0.85-1). The corresponding signals could therefore be fairly modelled assuming no saturation dependence of the SPC whatsoever; (b) the observations of exp #3 led to a SPC that can be larger than its value at saturation; (c) the observations of the exp #2 show a non-monotonous behaviour of the SPC as saturation decreases. The underlying physics of a non-monotonous SPC is related to water/air interfaces as shown by the results of the lattice Boltzmann numerical simulations. The main contribution to the SPC behaviour comes from the charged water/air interfaces and depends on the dynamic state of moving or entrapped bubbles. We finally describe the consequences of such a behaviour on the seismoelectric conversions for unsaturated conditions.

Electromagnetic/acoustic coupling in partially-saturated porous rocks: An extension of Pride's theory

“…In the last of these references, as it was previously suggested by Allègre et al (2014); Allégre et al (2015), it was shown through a numerical lattice-Boltzmann procedure that indeed the polarization of the air-water interface does play an important role both in the amplitude of the electrokinetic coupling and in its non monotonic behavior. These results were reaffirmed by the analysis performed by Jouniaux et al (2020) revisiting laboratory data published by different authors.…”

Electromagnetic/acoustic coupling in partially-saturated porous rocks: An extension of Pride's theory

“…These results were reaffirmed by the analysis performed by Jouniaux et al (2020) revisiting laboratory data published by different authors.…”

Numerical modeling of physical and biochemical processes in the subsurface and their impacts on the self-potential signature

“…Moreover, the signature is affected by the subsurface hydraulic and electrical properties (Hu et al, 2020). Thus, when combined with hydrological and biogeochemical processes, the SP technique can be specifically used to localize and quantify water flow (e.g., pumping test and water leakage) (Oliveti and Cardarelli, 2017) and redox-sensitive contaminant distribution (e.g., metallic and organic matter) (Revil et al, 2009;Forté and Bentley, 2013) and estimate soil hydraulic and electrical properties (e.g., hydraulic and electrical conductivity) (Jouniaux et al, 2020).…”