Influence of oil saturation upon spectral induced polarization of oil-bearing sands

Abstract

International audienceThe induced polarization model developed recently by Revil and Florsch to understand the complex conductivity of fully saturated granular materials has been extended to partial saturation conditions. It is an improvement over previous models like the Vinegar and Waxman model, which do not account explicitly for the effect of frequency. The Vinegar and Waxman model can be considered as a limiting case of the Revil and Florsch model in the limit where the distribution of relaxation times is very broad. The extended model is applied to the case of unconsolidated sands partially saturated with oil and water. Laboratory experiments were performed to investigate the influence of oil saturation, frequency, grain size, and conductivity of the pore water upon the complex resistivity response of oil-bearing sands. The low-frequency polarization (below 100 Hz) is dominated by the polarization of the Stern layer (the inner part of the electrical double layer coating the surface of the grains in contact with water). The phase exhibits a well-defined relaxation peak with a peak frequency that is dependent on the mean grain diameter as predicted by the model. Both the resistivity and the magnitude of the phase increase with the relative saturation of the oil. The imaginary (quadrature) component of the complex conductivity is observed to decrease with the oil saturation. All these observations are reproduced by the new model

Impact of changes in grain size and pore space on the hydraulic conductivity and spectral induced polarization response of sand

“…Pelton et al (1978) were arguably the first to illustrate the adequacy of Cole-Cole-type models (Cole and Cole, 1941) for phenomenological description of the monitored SIP responses (e.g., Vanhala, 1997;Dias, 2000). Recently, Revil and Florsch (2010) supplied a corresponding theoretical justification, which is based on the polarization of the Stern layer and supported by the results of several recent studies (Leroy et al, 2007;Jougnot et al, 2010;Schmutz et al, 2010). …”

Induced polarization signatures of cations exhibiting differential sorption behaviors in saturated sands

“…The field E represents the imposed electrical field, and J d (þ) represents the back-diffusion flux densities of the counterions of the Stern layer in their surface concentration gradient. porous media [Leroy et al, 2008;Leroy and Revil, 2009;Jougnot et al, 2010;Revil and Florsch, 2010;Schmutz et al, 2010]. However, it should be kept in mind that this assumption is untested.…”

“…According to Leroy et al [2008], Revil [2009], Jougnot et al [2010], Revil and Florsch [2010], and Schmutz et al [2010], the main mechanism of polarization in sand at low frequencies (below 100 Hz) corresponds to the polarization of the Stern layer at the pore water -mineral interface (the second contribution mentioned above). We develop here the equations for a porous material having a single polarization scale d 0 (the more general case corresponding to a distribution of polarization scales is discussed in Appendix A and section 5).…”

“…[3] Recently, Revil and colleagues [Leroy et al, 2008;Leroy and Revil, 2009;Jougnot et al, 2010;Revil and Florsch, 2010;Schmutz et al, 2010] have developed a fundamental theory connecting spectral induced polarization to the speciation of the mineral surface of silicates and aluminosilicates. Their theory is based on a description of the electrochemistry of the mineral surface and its connection with a Stern layer polarization model of the grains.…”

Quadrature conductivity: A quantitative indicator of bacterial abundance in porous media

“…The first is the contribution associated with the presence of the oil itself. As shown for instance by Schmutz et al (2010), Atekwana (2014), oil saturation and wettability play a central role in the SIP response of oil-bearing media.…”