Wavefield characteristics of seismoelectric effects in thin-interbeds

The Coseismic Field (CS) and the seismoelectric Interface Response (IR) generated by seismoelectric coupling have different signal strengths. The seismoelectric interface response which can reflect the interface information of the underground geological body is generally weaker than CS signals, while it may be strong in a thin-interbed geological case. At present, there is little detailed analysis on the wavefield characteristics of seismoelectric effects in thin interbeds, and whether the seismoelectric interface response caused by P-waves is sensitive to thin-interbeds remains to be examined. Based on the seismoelectric coupling theory of the charge per unit pore volume as an alternative to the zeta potential-based model, the wavefield characteristics of seismoelectric coupling are simulated under the geological background of horizontal and inclined thin-interbeds. Results show that the CS signals propagating along with the P-wave propagation are almost not affected by horizontal and wedge-shaped thin-interbeds. The IR field induced by P-waves at the interface are not sensitive to Vertical Thin-Interbeds (VTI), but the thickness and number of layers of Horizontal Thin-Interbeds (HTI) and wedge-shaped thin-interbeds have a notable effect on this field. The decrease of the thickness of a single layer in thin-interbeds and the increase of the number of layers of thin-interbeds can lead to the enhancement of IR signal. Results clearly prove that the seismoelectric interface response field caused by P-waves can produce an amplitude anomaly in thin-interbeds, also, the differences of seismoelectric wavefields between the horizontal and vertical thin-interbeds may have a potential to gain insight into the seismoelectric signal produced in shale or other reservoirs with significant differences in bedding direction.