Modeling Of Seismoelectric Effects In A Borehole
Name
1995.14 Haartsen_Toksoz.pdf
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1.29 MB
Format
Adobe PDF
Checksum (MD5)
cddebe0c1923e98c93be1603f8e4b573
Author(s)
Haartsen, Matthijs W.
Toksoz, M. N.
Date Issued
1995
Publisher
Massachusetts Institute of Technology. Earth Resources Laboratory
Series/Report no.
Earth Resources Laboratory Industry Consortia Annual Report;1995-14
Abstract
We present a method to simulate the propagation of seismic and converted electromagnetic
waves generated by a mechanical borehole source embedded in a layered poroelastic
medium. The electroseismic conversions occur at both the borehole wall and the layer
boundaries. Most studies in electroseismic effects have been modelled and tested with
seismic sources and detectors (geophones and antennas) at the surface. In this paper,
we investigate the case of a seismic source in a borehole and receivers either at the
surface or embedded in the medium. The method is formulated as a boundary element
technique (where the poroelastic displacement and relative flow Green's functions are
calculated by the discrete wavenumber method. The singular properties of the Green's
functions are determined analytically using static Green's functions to regularize the
integrals. This is necessary to calculate the element's self interaction. The borehole is
cylindrical and its axis rulls normal to the interfaces. The coupled electroseismic effects in the layered media are included by using the global matrix technique.
The developed method is an extension of the model of Biot-Rosenbaum, who applied
the wavenumber integration technique to investigate the effect of formation permeability
on Stoneley waves, using Biot's theory to model the wave propagation effects of a homogeneous permeable formation surrounding a borehole. We extend the Biot-Rosenbaum
model by including the effect of a heterogeneous permeable formation surrounding the
borehole. The effect of formation permeable zones (or fractured zones) on Stoneley
waves can now be investigated. The other modification is the inclusion of conversions of
mechanical into electromagnetic waves at mechanical and/or electrical contrasts in the
poroelastic formation. The converted electromagnetic fields are sensitive to large permeability contrasts and fluid chemistry contrasts inside a reservoir. Using the electroseismic method downhole will provide more information about permeability/permeability contrasts in the formation, as well as additional lithological information (salinity of the fluids).
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