Full-waveform simulation of multipole seismoelectric logging while drilling in a fluid-saturated porous formation

Seismic and electromagnetic wavefields are coupled in subsurface rocks due to the seismoelectric effect occurred in the electric double layer at the grain/fluid interface of porous formations. In this study, we simulate and investigate the borehole seismoelectric wavefields under logging while drilling (LWD) environment. An acoustic multipole source is assumed to radiate acoustic energy on the surface of the steel drilling collar located in the fluid-filled borehole. The seismoelectric field is calculated by solving a modified Poisson's equation, whose source term is the electric disturbance induced electrokinetically by the traveling seismic wave. The seismic wavefield itself is obtained by solving Biot's equations for poroelastic waves. By comparing the amplitudes of the collar wave in the acoustic-pressure and electric-filed full-waveforms, we found that the former is significantly weakened compared with the latter, in terms of its amplitude relative to the other wave groups in the full waveforms. Thus less and shallower grooves are required to damp the collar wave if the seismoelectric LWD signals are recorded for extracting formation compressional and shear velocities.