Geoscience Reference
In-Depth Information
response for a range of frequencies. If the target is a
fractured material, we can expect to see some resonance
effects associated with the focusing of the seismic waves
on the fractures (Figure 6.26). Jougnot et al. (2013) have
shown, indeed, that we could expect specific electrical
resonance effects when a crack is vibrated at particular
frequencies. Therefore, the spectral beamforming
method could be used to detect and characterize fractures
in a reservoir.
This method could also be applied to complex conduc-
tivity, which is known to contain information that
can be used to determine the permeability structure
between wells.
References
Farquharson, C.G. (2008) Constructing piecewise-constant
models in multidimensional minimum-structure inversions.
Geophysics
,
73
,K1
K9.
Hale, D. (2009a) Structure-oriented smoothing and sem-
blance. CWP Report, 635,
http://inside.mines.edu/~dhale/
pdf
[accessed on December 3, 2014].
Hale, D. (2009b) Image-guided blended neighbor interpola-
tion. CWP Report, 634,
http://inside.mines.edu/~dhale/
pdf
[accessed on December 3, 2014].
Hale, D. (2009c) Image-guided blended neighbor interpolation
of scattered data.
79th Annual International. Meeting, SEG
,
Expanded Abstracts
,
28
, 1127
-
6.5 Conclusions
Wehavedemonstrated that virtual electrodes canbeused,
at known positions and times, to image a heterogeneous
medium. This is achieved through the focusing of
acoustic waves at specific coordinates using multiple
acoustic receivers located in the vicinity of the target.
The acoustic energy at the focus time is the largest relative
to all other times, thus insuring the strongest possible
seismoelectric response at the target position. This
methodology can be used to investigate the electric and
hydraulic properties of a medium by surrounding the
area of investigation with multiple electrodes at known
positions. The dense virtual electrode distribution has
the potential to increase the robustness and improve the
resolutionof ERT. Thismethodology canalsobeemployed
to infer hydraulic parameters, for example, permeability,
through a controlled seismoelectric procedure.
Based on the beamforming approach, we can map
heterogeneities in resistivity between a set of wells. The
method we discussed in this chapter is based on scanning,
through seismic focusing, electrokinetic conversion, and
measurement of the electrical potential between two
wells. The focusing is done through the time reversal of
seismic waves using a set of seismic sources located in
two wells. The obtained
1131.
Jardani, A., Revil, A., Slob, E. & Söllner, W. (2010) Stochastic
joint inversion of 2D seismic and seismoelectric signals in
linear poroelastic materials.
Geophysics
,
75
(
1
), N19
-
-
N31,
doi:10.1190/1.3279833
Jougnot, D., Rubino J.G., Rosas Carbajal M., Linde N. & Holliger
K. (2013) Seismoelectric effects due to mesoscopic heteroge-
neities.
Geophysical
Research
Letters
,
40
,
2033
-
2037,
doi:10.1002/grl.50472.
Lelièvre, P.G. & Farquharson, C.G. (2013) Gradient and smooth-
ness regularization operators for geophysical inversion on
unstructured meshes.
Geophysical Journal International
,
178
,
623
637, doi: 10.1111/j.1365-246X.2009.04188.x.
Revil, A. & Cathles, L.M. (1999) Permeability of shaly sands.
Water Resources Research
,
35
(
3
), 651
-
662, 1999.
Revil, A. &Mahardika, H. (2013) Coupled hydromechanical and
electromagnetic disturbances in unsaturated porous materials.
Water Resources Research
,
49
(
2
), 744
-
-
766, doi:10.1002/
wrcr.20092.
Saunders, J.H., Jackson, M.D. & Pain, C.C. (2008) Fluid flow
monitoring in oilfields using downhole measurements of
electrokinetic potential.
Geophysics
,
73
, E165
contains
structural information regarding the heterogeneities in
the scanned volume. The resulting seismoelectric-based
heterogeneity image can then be used to constrain
resistivity tomography using image-guided inversion to
impose structural constraints in the model covariance
matrix. This approach opens a new perspective on the
imaging of a fine resistivity structure between wells
and then, using the derived resistivity structure, to
convert the data into petrophysical properties of interest.
“
seismoelectric image
”
E180.
Sava, P. & Revil, A. (2012) Virtual electrode current injection
using seismic focusing and seismoelectric conversion.
Geophys-
ical Journal International
,
191
,
3
, 1205
-
-
1209, doi: 10.1111/
j.1365-246X.2012.05700.x.
Zhou, J., Revil, A., Karaoulis, M., Hale, D., Doetsch, J. &
Cuttler, S. (2014) Image-guided inversion of electrical
resistivity data.
Geophysical Journal International
,
197
,292
-
309,
doi:10.1093/gji/ggu001
