Massachusetts Institute of Technology. Earth Resources Laboratory
Abstract
The seismoelectric logging method is based on measuring the electric field generated
by seismic waves in a fluid-filled borehole. Two kinds of electromagnetic (EM) fields
can be generated within the formation and at the interface of formations. One is a
stationary or local EM wave and the other is a radiating EM wave. In this paper, we
make various fractured borehole models with artificial materials or natural rocks and
measure the electric field generated by a seismic source in a water-filled borehole. The
experimental results show that the Stoneley wave generates both a stationary EM wave
at the borehole wall and a radiating EM wave on the fracture, which propagates with
light speed in the borehole. When the aperture of the fracture increases, the amplitude
of the seismoelectric wave decreases due to the low ion concentration in the fracture.
In a layered borehole model, a thin, permeable glued-sand zone is sandwiched between
two nonpermeable or low-permeable layers, and the Stoneley wave generates two kinds
of seismoelectric signals at the permeable zone. Compared with the acoustic waveforms
in the same borehole, the seismoelectric waveforms are more effective in determining
and characterizing a fracture or a fractured zone filled with a permeable layer.Massachusetts Institute of Technology. Borehole Acoustics and Logging ConsortiumMassachusetts Institute of Technology. Earth Resources Laboratory. Reservoir Delineation
ConsortiumUnited States. Dept. of Energy (Grant DE-FG0293ERl4322
