Seismoelectric Laboratory Measurements In A Borehole
Name
1998.10 Zhu_Toksoz.pdf
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360.27 KB
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Adobe PDF
Checksum (MD5)
3278a72864477e92b82914f0f54fe3e7
Author(s)
Zhu, Zhenya
Toksoz, M. Nafi
Date Issued
1998
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1998-10
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.
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