Seismoelectric Coupling Research Articles

Seismoelectric wave propagation through a fluid-saturated porous sandwiched interlayer

The seismoelectric waves generated in a fluid-saturated porous interlayer and the reflection/transmission characteristics at the interfaces of sandwiched structure are studied in this paper. Aiming to describe the strong attenuation and dispersion simultaneously at seismic and sonic frequencies, a new fractional viscoelastic model for the solid skeleton is introduced to the Pride's seismoelectric coupling theory. Using the interfacial continuity of stress, displacements, magnetic and electric fields, the reflection/transmission coefficients are determined. The numerical results are provided and shown graphically. The effects of seismoelectric coupling and the viscoelastic characteristics of solid skeleton on the reflection and transmission of seismoelectric waves are mainly studied. It is observed that the thickness, porosity and the viscoelastic characteristics of solid skeleton have evident effects not only on the electromagnetic waves but also on the seismic waves.

Seismoelectric Coupling Equations of Oil-Wetted Porous Medium Containing Oil and Water

For porous medium containing multiphase fluid, such as oil-wetted porous medium with oil–water dual phase fluid, its fluid interface will also produce electric double layer (EDL), which will play a role in the seismoelectric effects. At this time, the principle of seismoelectric effects is more complex. The existing theory for the seismoelectric effects is the Pride theory used in the water-saturated porous formation, which cannot meet the actual needs of the theoretical research of seismoelectric exploration in the porous formation with multiphase fluid. Carbonate porous formations are often oil-wetted; therefore, it is necessary to study the electrokinetic effects of oil-wetted porous medium containing multiphase fluid. In this paper, we treated the oil–water mixture as an effective fluid, and solved the effective elastic parameters and extended the Biot equations to the case of oil-wetted porous medium with oil–water dual phase fluid. We calculated the effective electromagnetic parameters and derived the macroscopic coupling equations of seismoelectric effects and electroseismic effects, and proposed the new electrokinetic coupling coefficients of the oil-wetted porous medium with dual phase fluid. We also deduced the coupling functions of electric and magnetic fields relative to the solid displacement in the homogeneous porous medium, and studied the polarization characteristics of the electric field. We use the derived coupling equations to simulate the seismoelectric logging while drilling in the model of oil-wetted porous formation with dual phase fluid under the excitation of multipole sources. The influence of drill collar wave on the acoustic field and electric field under the excitation of different sources was investigated, which has a certain guiding role in the selection of electrokinetic logging tools.

Numerical investigation on seismoelectric wave fields in porous media: porosity and permeability

Abstract Compared with the seismic wave fields, the influence of porosity and permeability to seismoelectric coupling may be more significant. The seismoelectric effect mainly forms the coseismic signals (CS) and interface response (IR). The influences of the porosity and permeability on the two types of seismoelectric field are still not clear. In this paper, we numerically analyze the response characteristics of the CS and IR with the dependency of porosity and permeability, respectively. The differences in the sensitivity of the CS and the IR fields to porosity and permeability are also determined. The results show that the change of permeability is mainly sensed by the IR field, while the CS has almost no obvious response to it: both the CS and IR fields are sensitive to the change of porosity, but the sensitivity of the IR field is higher and with the increase of porosity, the discrepancy between the sensitivity of the CS and IR fields to porosity changes increases. The signal amplitude anomaly will be caused in both P-wave fields and seismoelectric fields (IR and CS) at the geological body where the porosity changes, but the change of permeability has little impact on the P-wave and only induces an obvious IR amplitude anomaly in seismoelectric fields. This indicates that the seismoelectric effect can better reveal the connectivity characteristics of the geological body than the seismic wave. This investigation can help to distinguish the sensitivity of seismoelectric response to porosity and permeability more clearly.

Study of the Seismoelectric Effect in Saturated Porous Media Using a Bundle of Capillary Tubes Model

The seismoelectric effect is the fundamental basis for seismoelectric logging. Most of the existing theories for the seismoelectric effect are based on the Pride theory, which adopts the assumption of a thin electric double layer and uses the volume-averaging method to derive the seismoelectric coupling equations; hence, the obtained electrokinetic coupling coefficient is not applicable to large-Debye-length cases. In addition, the Pride theory neglects the change in seepage velocity with the radial position of the pore when calculating the streaming current, which leads to an inaccurate reflection of the influence of pore size on the electrokinetic coupling coefficient. In this study, we proposed a flux-averaging method to solve the effective net residual charge density of porous media and further derived the electrokinetic coupling coefficient expressed by the effective net residual charge density. We also investigated the effect of formation parameters and compared the results with those calculated using the Pride theory. Since the proposed method is not limited by the thin electric double layer assumption, it is suitable for both small- and large-Debye-length cases. Moreover, we also carried out flume experiments to investigate the influence of salinity, where both thin and thick electric double layer cases were studied. The comparison between the results of the experiment and simulation verified the correctness of the proposed method. Furthermore, the proposed method took into account the variation in seepage velocity with pore location when solving for the streaming current; therefore, the influence of the pore size on the electrokinetic coefficient can be described more accurately.

Experimental studies on the mechanism of seismoelectric logging while drilling with multipole source

SUMMARYWhen a seismic wave propagates in a fluid-saturated porous medium, a relative movement forms between the solid and the fluid and induces an electric current due to the electronic double layer. As a result, two kinds of seismoelectric coupling responses are generated in this procedure: the localized electric/magnetic field and interfacial electromagnetic wavefield. One important potential application of these two seismoelectric conversions is used for measuring formation P and S waves in well logging. Considering that the strong collar wave seriously affects the velocity measurements of formation P and S waves in current acoustic logging while drilling (LWD), the seismoelectric LWD method, which combines seismoelectric conversion and acoustic LWD technique, was suggested to be a novel method in oil and gas exploration. The collar wave cannot induce any seismoelectric signal on the metal collar since there is no double layer formed on a metal surface. In this paper, acoustic and seismoelectric LWD measurements are conducted in the laboratory. We build a scaled multipole acoustic LWD tool to conduct acoustic measurements in a water tank and a sandstone borehole model. We also build a multipole seismoelectric LWD tool and record the seismoelectric signals induced with the same acoustic source. Then, we compare the recorded acoustic and seismoelectric signals by using the experimental data. The result indicates that the apparent velocities of seismoelectric signals are equal to the formation P- and S-wave velocities and the collar waves do not induce any visible electric signal in the full waveforms. We further analyse the mechanism of seismoelectric LWD by a quantitative comparison of the amplitudes between the inner collar wave and outer collar wave. The results show that the amplitude of outer collar wave decreases significantly when it radiates out of the tool, so that the seismoelectric signals induced by collar waves are too weak to be distinguished in the full waveforms of seismoelectric LWD measurements. Thus, the formation P- and S-wave velocities are detected accurately from the recorded seismoelectric LWD data. These results verify the feasibility of the seismoelectric LWD method for measuring acoustic velocities of the borehole formation.

Seismo-electric conversion in shale: experiment and analytical modelling

SUMMARY The development of seismo-electric exploration techniques relies critically upon the strength of the seismo-electric conversion. However, there have been very few seismo-electric measurements or modelling on shales, despite shales accounting for the majority of unconventional reservoirs. We have carried out seismo-electric measurements on Sichuan Basin shales (permeability 0.00147–0.107 mD), together with some comparative measurements on sandstones (permeability 0.2–60 mD). Experimental results show that the amplitudes of the seismo-electric coupling coefficient in shales are comparable to that exhibited by sandstones, and are approximately independent of frequency in the seismic frequency range (<1 kHz). Numerical modelling has also been used to examine the effects of varying (i) dimensionless number, (ii) porosity, (iii) permeability, (iv) tortuosity and (v) zeta potential on seismo-electric conversion in porous media. It was found that while changes in dimensionless number and permeability seem to have little effect, seismo-electric coupling coefficient is highly sensitive to changes in porosity, tortuosity and zeta potential. Numerical modelling suggests that the origin of the seismo-electric conversion in shales is enhanced zeta potentials caused by clay minerals, which are highly frequency dependent. This is supported by a comparison of our numerical modelling with our experimental data, together with an analysis of seismo-electric conversion as a function of clay mineral composition from XRD measurements. The sensitivity of seismo-electric coupling to the clay minerals suggests that seismo-electric exploration may have potential for the characterization of clay minerals in shale gas and shale oil reservoirs.

Measurements of the seismoelectric responses in a synthetic porous rock

SUMMARY Seismoelectric measurements are conducted with a synthetic porous rock sample to model an ocean exploration. Two kinds of seismoelectric coupling signals, that is, the interfacial EM wave signal and the coseismic electric signal, have been recorded by the electrodes buried inside a rock sample instead of those located in the fluid or in the solid region near the interface as performed in previous works. These seismoelectric signals are clearly observed and identified with a high signal-to-noise ratio. The characteristics of the measured interfacial EM wave and coseismic electric signals are analysed with the experimental data. We also simulate the seismoelectric conversion fields and make a comparison between the measured and simulated seismoelectric signals. The result shows that the simulated and measured signals match well for both the interfacial EM wave and the coseismic electric fields accompanying the fast P wave. Our results also show that the amplitudes of seismoelectric signals are in the order of tens to hundreds of microvolts with our experimental system. This confirms that the seismoelectric signals are measurable in the interior of the rocks with current measurement techniques, suggesting the seismoelectric measurement to be a potential method for studying characteristics of the material beneath the seafloor.

The effect of rock permeability and porosity on seismoelectric conversion: experiment and analytical modelling

SUMMARYThe seismoelectric method is a modification of conventional seismic measurements which involves the conversion of an incident poroelastic wave to an electromagnetic signal that can be measured at the surface or down a borehole. This technique has the potential to probe the physical properties of the rocks at depth. The problem is that we currently know very little about the parameters which control seismoelectric conversion and their dependence on frequency and permeability, which limits the development of the seismoelectric method. The seismoelectric coupling coefficient indicates the strength of seismoelectric conversion. In our study, we focus on the effects of the reservoir permeability, porosity and frequency on the seismoelectric coupling coefficient through both experimental and numerical modellings. An experimental apparatus was designed to record the seismoelectric signals induced in water-saturated samples in the frequency range from 1 to 500 kHz. The apparatus was used to measure seismoelectric coupling coefficient as a function of porosity and permeability. The results were interpreted using a microcapillary model for the porous medium to describe the seismoelectric coupling. The relationship between seismoelectric coupling coefficients and the permeability and porosity of samples were also examined theoretically. The combined experimental measurements and theoretical analysis of the seismoelectric conversion has allowed us to ascertain the effect of increasing porosity and permeability on the seismoelectric coefficient. We found a general agreement between the theoretical curves and the test data, indicating that seismoelectric conversion is enhanced by increases in porosity over a range of different frequencies. However, seismoelectric conversion has a complex relationship with rock permeability, which changes with frequency. For the low-permeability rock samples (0–100 × 10−15 m2), seismoelectric coupling strengthens with the increase of permeability logarithmically in the low-frequency range (0–10 kHz); in the high-frequency range (10–500 kHz), the seismoelectric coupling is at first enhanced, with small increases of permeability leading to small increases in size in electric coupling. However, continued increases of permeability then lead to a slight decrease in size and image conversion again. For the high-permeability rock samples (300 × 10−15–2200 × 10−15 m2), the seismoelectric conversion shows the same variation trend with low-permeability samples in low-frequency range; but it monotonically decreases with permeability in the high-frequency range. The experimental and theoretical results also indicate that seismoelectric conversion seems to be more sensitive to the changes of low-permeability samples. This observation suggests that seismic conversion may have advantages in characterizing low permeability reservoirs such as tight gas and tight oil and shale gas reservoirs.

Quantitative Understanding on the Amplitude Decay Characteristic of the Evanescent Electromagnetic Waves Generated by Seismoelectric Conversion

We conduct numerical simulations and theoretical analyses to quantitatively study the amplitude decay characteristic of the evanescent electromagnetic (EM) waves, which has been neglected in previous studies on the seismoelectric conversion occurring at a porous–porous interface. Time slice snapshots of seismic and EM wave-fields generated by a vertical single force point source in a two-layer porous model show that evanescent EM waves can be induced at a porous–porous interface. The seismic and EM wave-fields computed for a receiver array located in a vertical line nearby the interface are investigated in detail. In addition to the direct and interface-response radiation EM waves, we identify three groups of coseismic EM fields and evanescent EM waves associated with the direct P, refracted SV–P and direct SV waves, respectively. Thereafter, we derive the mathematical expression of the amplitude decay factor of the evanescent EM waves. This mathematical expression is further validated by our numerical simulations. It turns out the amplitude decay of the evanescent EM waves generated by seismoelectric conversion is greatly dependent on the horizontal wavenumber of seismic waves. It is also found the evanescent EM waves have a higher detectability at a lower frequency range. This work provides a better understanding on the EM wave-fields generated by seismoelectric conversion, which probably will help improve the interpretation of the seismoelectric coupling phenomena associated with natural earthquakes or possibly will inspire some new ideas on the application of the seismoelectric coupling effect.

Seismoelectric interface electromagnetic wave characteristics for the finite offset Vertical Seismoelectric Profiling configuration: Theoretical modeling and experiment verification.

The seismoelectric interface electromagnetic characteristics have been studied for the finite offset Vertical Seismoelectric Profiling (VSEP) configuration. The approach consists of theoretical modeling and laboratory verification. The results show that the wave variation characteristics along the finite offset measurement line are markedly different from those along the zero-offset line. More interestingly, the wave characteristics for both configurations can be satisfactorily explained by the electric dipole model for the seismoelectric interface wave radiation. Besides, the experiment confirms the modeling result based on the seismoelectric coupling theory and validates the VSEP technique as an effective method for subsurface interface delineation.

Influence of Saturant on Seismoelectric Coupling Response of Porous Media

The seismoelectric coupling phenomenon in porous medium saturated with gas and water was studied numerically. The numerical model was formulated based on Pride's theoretically developed seismoelectric coupling coefficient that describes conversion of seismic energy into electromagnetic radiation. The conversion is complex function of physical, electrical and poroelastic properties of the porous medium and the saturant. In this study, a porous medium that is partially saturated with water is considered. Pore spaces that are not saturated with water are considered to be filled with gas. The gas phase is methane. The water saturation was varied from 0.2 to 0.9. The physical and electrical properties of both phases are determined at a temperature of 325 °K. The porosity and permeability of the porous medium is 0.2 and 500 mD, respectively. The porous medium in this study is isotropic. Zeta potential was estimated using an empirically derived correlation. At 0.001 mol/lit salinity, zeta potential is 66.7 mv. The numerical study result shows that at a fixed seismic wave frequency, lower water saturation results in higher seismoelectric coupling coefficient. When water saturation increases, the seismoelectric coupling coefficient decreases. However, the rate of decline is lower at higher seismic frequency. The rate of decline at 10 kHz is 1.38 nV/Pa compared to 4.35 nV/Pa at 100 kHz. Higher frequencies result in stronger nonlinearities, which causes higher mechanical energy dissipation. As such, the result obtained in this study is consistent with what is normally expected when mechanical wave propagates through a porous media.

Numerical Study of Frequency-dependent Seismoelectric Coupling in Partially-saturated Porous Media

The seismoelectric phenomenon associated with propagation of seismic waves in fluid-saturated porous media has been studied for many decades. The method has a great potential to monitor subsurface fluid saturation changes associated with production of hydrocarbons. Frequency of the seismic source has a significant impact on measurement of the seismoelectric effects. In this paper, the effects of seismic wave frequency and water saturation on the seismoelectric response of a partially-saturated porous media is studied numerically. The conversion of seismic wave to electromagnetic wave was modelled by extending the theoretically developed seismoelectric coupling coefficient equation. We assumed constant values of pore radius and zeta-potential of 80 micrometers and 48 microvolts, respectively. Our calculations of the coupling coefficient were conducted at various water saturation values in the frequency range of 10 kHz to 150 kHz. The results show that the seismoelectric coupling is frequency-dependent and decreases exponentially when frequency increases. Similar trend is seen when water saturation is varied at different frequencies. However, when water saturation is less than about 0.6, the effect of frequency is significant. On the other hand, when the water saturation is greater than 0.6, the coupling coefficient shows monotonous trend when water saturation is increased at constant frequency.

A Preliminary Result of Seismoelectric Responses Study on Shallow Fluid-Saturated Layer: Numerical Modeling Using Transfer Function Approach

Seismoelectric phenomena occurs when a seismic wave propagating in a fluid-saturated medium and crossing an interface of different fluid-saturated mediums that induces electrical field or cause radiation of an electromagnetic wave where only the electric part is being measured. In this paper, we present our research progress on seismoelectric imaging of shallow fluid-saturated layers. The progress mainly discusses on our finite-difference algorithm which provides an alternative method to simulate seismic wave propagation in fluid saturated porous media generating electric fields through an electrokinetic mechanism called seismoelectric coupling. The target of this numerical simulation is to see whether the seismoelectric responses of coseismic field and interface boundary effect can be image on the seismoelectrogram. The simulation begins with the calculation of seismic displacement by using the classical homogeneous formulation. Next, we calculate the seismoelectric responses using the seismoelectric transfer function. The algorithm is then used to simulate seismoelectric responses created from various conditions of finite-infinite and finite-infinite sand-clay model, surface to downhole and crosshole configurations.

Experimental quantification of the seismoelectric transfer function and its dependence on conductivity and saturation in loose sand

ABSTRACTUnder certain circumstances, seismic propagation within porous media may be associated to the conversion of mechanical energy to electromagnetic energy, which is known as a seismo‐electromagnetic phenomenon. The propagation of fast compressional P‐waves is more specifically associated to the manifestations of a seismoelectric field linked to the fluid flows within the pores. The analysis of seismoelectric phenomena, which requires the combination of the theory of electrokinetics and Biot's theory of poroelasticity, provides us with transfer function that links the coseismic seismoelectric field E to the seismic acceleration . To measure the transfer function, we have developed an experimental setup enabling seismoelectric laboratory observation in unconsolidated quartz sand within the kilohertz range. The investigation focused on the impact of fluid conductivity and water saturation over the coseismic seismoelectric field. During the experiment, special attention was given to the accuracy of electric field measurements. We concluded that, to obtain a reliable estimate of the electric field amplitude, the dipole from which the potential differences are measured should be of much smaller length than the wavelength of the propagating seismic field. Time‐lapse monitoring of the seismic velocities and seismoelectric transfer functions were performed during imbibition and drainage experiments. In all cases, the quantitative analysis of the seismoelectric transfer function was in good agreement with theoretical predictions. While investigating saturation variations from full to residual water saturation, we showed that the ratio undergoes a switch in polarity at a particular saturation , which also implies a sign change of the filtration, traducing a reversal of the relative fluid displacement with respect to the frame. This sign change at critical saturation stresses a particular behaviour of the poroelastic medium: the dropping of the coseismic electric field to zero traduces the absence of relative pore/fluid displacements representative of a Biot dynamically compatible medium. We concluded from our experimental study in loose sand that the measurements of the coseismic seismoelectric coupling may provide information on fluid distribution within the pores and that the reversal of the seismoelectric field may be used as an indicator of the dynamically compatible state of the medium.

Experimental research on seismoelectric effects in sandstone

The seismoelectric effects induced from the coupling of the seismic wave field and the electromagnetic field depend on the physical properties of the reservoir rocks. We built an experimental apparatus to measure the seismoelectric effects in saturated sandstone samples. We recorded the seismoelectric signals induced by P-waves and studied the attenuation of the seismoelectric signals induced at the sandstone interface. The analysis of the seismoelectric effects suggests that the minimization of the potential difference between the reference potential and the baseline potential of the seismoelectric disturbance area is critical to the accuracy of the seismoelectric measurements and greatly improves the detectability of the seismoelectric signals. The experimental results confirmed that the seismoelectric coupling of the seismic wave field and the electromagnetic field is induced when seismic wave propagating in a fluid-saturated porous medium. The amplitudes of the seismoelectric signals decrease linearly with increasing distance between the source and the interface, and decay exponentially with increasing distance between the receiver and the interface. The seismoelectric response of sandstone samples with different permeabilities suggests that the seismoelectric response is directly related to permeability, which should help obtaining the permeability of reservoirs in the future.

Numerical investigation of parameters affecting seismoelectric coupling coefficient in partially-saturated porous media

Numerical investigation of parameters affecting seismoelectric coupling coefficient in partially-saturated porous media

Seismoelectric measurements in a porous quartz‐sand sample with anisotropic permeability

ABSTRACTSeismoelectric coupling coefficients are difficult to predict theoretically because they depend on a large numbers of rock properties, including porosity, permeability, tortuosity, etc. The dependence of the coupling coefficient on rock properties such as permeability requires experimental data. In this study, we carry out a set of laboratory measurements to determine the dependence of seismoelectric coupling coefficient on permeability. We use both an artificial porous “sandstone” sample, with cracks, built using quartz‐sand and Berea sandstone samples. The artificial sample is a cube with 39% porosity. Its permeability levels are anisotropic: 14.7 D, 13.8 D, and 8.3 D in the x‐, y‐, and z‐directions, respectively. Seismoelectric measurements are performed in a water tank in the frequency range of 20 kHz–90 kHz. A piezoelectric P‐wave source is used to generate an acoustic wave that propagates through the sample from the three different (x, y, and z) directions. The amplitudes of the seismoelectric signal induced by the acoustic waves vary with the direction. The highest signal is in the direction of the highest permeability, and the lowest signal is in the direction of the lowest permeability. Since the porosity of the sample is constant, the results directly show the dependence of seismoelectric coefficients on permeability. Seismoelectric measurements with natural rocks are performed using Berea sandstone 500 and 100 samples. Because the Berea samples are nearly isotropic in permeability, the amplitudes of the seismoelectric signals induced in the different directions are the same within the measurement error. Because the permeability of Berea 500 is higher than that of Berea 100, the amplitude of the seismoelectric signals induced in Berea 500 is higher than those in Berea 100. To determine the relative contributions of porosity and permeability on seismoelectric conversion, we carried out an analysis, using Pride (1994) formulation and Kozeny–Carman relationship; the normalized amplitudes of seismoelectric coupling coefficients in three directions are calculated and compared with the experimental results. The results show that the seismoelectric conversion is related to permeability in the frequency range of measurements. This is an encouraging result since it opens the possibility of determining the permeability of a formation from seismoelectric measurements.

Seismoelectric coupling in unsaturated porous media: theory, petrophysics, and saturation front localization using an electroacoustic approach

The seismoelectric method is based on the interpretation of the electrical field associated with the conversion of mechanical to electromagnetic energy during the propagation of seismic waves in heterogeneous porous media. We propose an extension of a poroacoustic model that takes into account fluid flow and the effect of saturation. This model is coupled with an electrokinetic model accounting for the effect of saturation and in agreement with available experimental data in sands and carbonate rocks. We also developed new scaling laws for the permeability, the streaming potential coupling coefficient and the capillary entry pressure of porous media. The theory is developed for frequencies much below the critical frequency at which inertial effects starts to dominate in the Navier–Stokes equation (>10 kHz). The equations used to compute the propagation of the P waves and the seismoelectric effect in unsaturated condition are solved with finite elements using triangular meshing. We demonstrate the usefulness of a recently developed technique, seismoelectric beamforming, to localize saturation fronts by focusing seismic waves and looking at the resulting seismoelectric conversions. This method is applied to a cross-hole problem showing how a saturation front characterized by a drop in the electrical conductivity and compressibility is responsible for seismoelectric conversions. These conversions can be used, in turn, to determine the position of the front over time.

Electric effects induced by artificial seismic sources at Somma-Vesuvius volcano

<p>In this paper, we present a series of self-potential measurements at Somma-Vesuvius volcanic area acquired in conjunction with an active seismic tomography survey. The aim of our study is both to provide further confirmation to the occurrence of seismo-electric coupling and to identify sites suitable for self-potential signal monitoring at Somma-Vesuvius district. The data, which were collected along two perpendicular dipoles, show significant changes on the natural electric field pattern. These variations, attributable to electrokinetic processes triggered by the artificial seismic waves, were observed after explosions occurred at a distance less than 5 km from the SP dipole arrays. In particular, we found that the NW-SE component of the natural electric field was more sensible to the shots than the NE-SW one, and the major effects did not correspond to the nearest shots. Such evidences were interpreted considering the underground electrical properties as deduced by previous detailed resistivity and self-potential surveys performed in the study area.</p>

Seismoelectric wave propagation numerical modelling in partially saturated materials

To better understand and interpret seismoelectric measurements acquired over vadose environments, both the existing theory and the wave propagation modelling programmes, available for saturated materials, should be extended to partial saturation conditions. We propose here an extension of Pride's equations aiming to take into account partially saturated materials, in the case of a water-air mixture. This new set of equations was incorporated into an existing seismoelectric wave propagation modelling code, originally designed for stratified saturated media. This extension concerns both the mechanical part, using a generalization of the Biot-Gassmann theory, and the electromagnetic part, for which dielectric permittivity and electrical conductivity were expressed against water saturation. The dynamic seismoelectric coupling was written as a function of the streaming potential coefficient, which depends on saturation, using four different relations derived from recent laboratory or theoretical studies. In a second part, this extended programme was used to synthesize the seismoelectric response for a layered medium consisting of a partially saturated sand overburden on top of a saturated sandstone half-space. Subsequent analysis of the modelled amplitudes suggests that the typically very weak interface response (IR) may be best recovered when the shallow layer exhibits low saturation. We also use our programme to compute the seismoelectric response of a capillary fringe between a vadose sand overburden and a saturated sand half-space. Our first modelling results suggest that the study of the seismoelectric IR may help to detect a sharp saturation contrast better than a smooth saturation transition. In our example, a saturation contrast of 50 per cent between a fully saturated sand half-space and a partially saturated shallow sand layer yields a stronger IR than a stepwise decrease in saturation.