Geoscience Reference
In-Depth Information
CHAPTER 8
Conclusions and perspectives
In the previous chapters, we developed the main
concepts behind the seismoelectric theory, including its
petrophysical foundations, the macroscopic field equa-
tions, their implementation in a finite-element package
to simulate forward problems, and some algorithms to
perform inverse problems. The theory has been described
in water-saturated conditions and extended to the par-
tially saturated case and two-phase flow conditions. This
allows the theory described in this topic to be very gen-
eral and versatile regarding geophysical applications.
That said, the applications of the seismoelectric methods
in environmental geosciences are still in their infancy,
and very few commercially available equipment exist
to democratize the method among geophysicist and non-
geophysicists. We discuss below eight challenges that will
need to be investigated in the next years:
1 The first challenge is related to the definitions of clear
protocols and equipment sensitivity to perform field
measurements. Seismoelectric conversion can be
measured in the field. This has been demonstrated in
a number of published case studies that were briefly
outlined in this topic. Because the seismoelectric
method is an active method, stacking can be used to
improve the signal-to-noise ratio. There is, however,
the need to define clear operational protocols to record
seismoelectric signals in the field and to define what
type of equipment is required to get clear signals. Once
such protocols are available, there is a need to further
explore the seismoelectric method with various
near-surface applications. We choose to work on
near-surface applications first, because the seismo-
electric conversions are expected to be relatively strong
where the conversions are taking place in the vicinity
of the receivers (<100 m). Any application in environ-
mental geosciences that studies electrical double layer
properties remotely could benefit from seismoelectric-
based investigations. These include contaminant
plumes, CO 2 sequestration, and the use of specific
tracers to follow flow paths in shallow aquifers. This
will require further developments in time-lapse seis-
moelectric investigations using, for instance, the
active-time constrained approach recently applied to
a number of geophysical methods or the fully coupled
inversion approach. In the first case, the objective
function to minimize contains a time-dependent
regularizer. The regularization is done in time like it
is classically done in space using deterministic algo-
rithms. In the second case, we need first to be able to
predict geophysical data using the modeling of the
process we wish to monitor. Then we use the geophys-
ical data to optimize some of the fundamental
parameters controlling these processes.
2 The second challenge is the separation of different con-
tributions of the seismoelectric phenomena that
appear in real, field-based, electrical potential (electro-
magnetic) time series data. These contributions
include the signals associated with the seismic source,
the coseismic effects, and the seismoelectric conver-
sions. We have shown in this topic that all of these
contributions can be properly modeled, and therefore,
 
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