Heat, temperature, stress and pathways as well as chemical
and mineralogical
composition of rocks hosting geothermal systems are, besides
the structural
inventory of the subsurface, the key elements that could be
put as priority for
research needs in geothermal investigation for EGS. Several
physical
parameters of roks, e.g., density, wave velocity, electrical
resistivity, are
coupled with temperature and can be imaged by various
geophysical methods.
Geophysics may also help in the reconstruction of stress
distribution at depth,
which is known to influence hydrofracturing. Moreover, the
presence of fluids
and pathways produce a sensible anomaly of different
physical properties, with
the limitations of depths of penetration and resolution.
Geophysical methods are suitable to determine the
architecture, geometry, and
quality of target intervals. However, improvement of
existing methods and in
particular reasonable combination of different, most
sensitive techniques are
needed to meet the requirements of modern geophysical
exploration.
Experiences made in hydrocarbon exploration, as well as in
volcanology,
nuclear waste disposal or CO2 sequestration must be modified
for EGS, and
coupled with the existing knowledge in geology and
geochemistry in order to
develop an integrated interpretation of different physical
parameters.
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