Guided Seismoelectric Wave Propagation in and at Confined Geological Units

In a finite-element modelling study we investigate the spatio-temporal occurrence and evolution of seismoelectric effects that result from seismic excitation in spatially confined geological units, which may be representative of clay lenses embedded in an aquifer or petroleum deposits in a host rock. We focus on the seismoelectric interface response, which proves to be guided within (closed waveguides) and around/along (transmission line) the geological boundaries depending on the contrast of relevant petrophysical parameters. We varied the contrast in the elastic module and the electric bulk conductivity for different embedded stratigraphic rock sequences. The results reveal a doubly coupled relationship between the elastic (seismic reflection or refraction case) and electric parameter contrast (perfect electric conductor or isolator) in correlation with the converting geometry of the geological structure, which is controlling shape and morphology of the seismic-to-electromagnetic field conversion in and at confined lithological units. Our numerical study shows that the guided seismoelectric interface response captures characteristics of the converting geological unit, indicating the potential of the seismoelectric method in particular for exploration of confined targets.