Experimental studies of seismoelectric conversions in fluid‐saturated porous media

Abstract

Abstract. When seismic waves generate a relative fluid-solid motion in a fluidsaturated porous medium, the moving charges (streaming current) in the electric double layer induce an electroma. gnetic (EM) field. This paper first experimentally confirms that the coupling between the seismic wave and the electromagnetic field in the kilohertz range is electrokinetic in nature. Seismoelectric signals are measured in homogeneous cylindrical porous rock samples and multilayered models. The seismoelectric signals in homogeneous rock are electric fields that move along with the acoustic wave. The mechanism of the seismoelectric conversion is completely different from the piezoelectric effect of quartz grains. The seismoelectric sensitivity with respect to salinity of the saturant has been experimentally determined. The amplitude of seismoelectric signals increases as the saturant conductivity decreases. The seismoelectric effects are generated by two different mechanisms. Both the EM radiation and the electric potential generated at an interface and within a porous medium, respectively, were measured as the P wave, at ultrasonic frequencies, passes through the layered models. Our experimental results demonstrate that seismoelectric effects exist and are measurable in the kilohertz range. The paper concludes with a comparison of experimental data and modeled data in a threelayer porous model. Seismoelectric measurements could be an effective means of obtaining transport coefficients such as hydraulic permeability and other porous rock properties.

Laboratory measurements and theoretical modeling of seismoelectric interface response and coseismic wave fields

“…[3][4][5][6][7] Furthermore, a wide range of field and laboratory validations of the coseismic field and the interface response was presented in the literature. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] Several of these works compare either field measurements 15,17 or laboratory measurements 20 with a seismoelectric wave propagation model, corroborating that the coseismic and interface response fields are predicted by the theory.…”

“…20 by developing a full waveform seismoelectric model for the coseismic and interface response fields based on the Sommerfeld integral, and comparing the numerical predictions with laboratory measurements. We demonstrate the seismoelectric nature of the measured electric potentials in a control experiment.…”

A review on electrokinetically induced seismo-electrics, electro-seismics, and seismo-magnetics for Earth sciences

“…When performing magnetic measurements it is necessary to use nonmetallic materials, because of their possible even small displacements within the ambient magnetic field. Measurements performed on dry samples showed that both the electric field and the magnetic field are within the noise level (Zhu et al, 2000;Bordes et al, 2008).…”

“…In most of the studies piezoelectric transducers are used to generate P waves and S waves. Although the centre frequencies of the transducers are several hundreds of kHz, the centre of frequencies of the propagating wave can be about 20 kHz (Zhu et al, 2000), because of attenuation. The acoustic transducers are driven by an electric pulse, whose width is adjustable usually to the half period of the recorded acoustic wave and can be in the range of 10-100 µs.…”

“…Electrodes can be made of conducting glue of 0.2 cm of diameter (Zhu et al, 2000), of platinum discs, of impolarizable silver/silver chloride rod, or mesh.…”