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| Titel |
Characterization of geothermal paleosystem in the Lesser Antilles volcanic arc: structural, petrographic, thermodynamic and petrophysics analysis of Terre-de-Haut (Les Saintes archipelago, Lesser Antilles) |
| VerfasserIn |
Alexiane Favier, Vivien Navelot, Chrystèle Verati, Jean-Marc Lardeaux, Michel Corsini, Marc Diraison, Yves Geraud, Jeanne Mercier de Lépinay, Marc Munschy |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250153885
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| Publikation (Nr.) |
 EGU/EGU2017-18920.pdf |
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| Zusammenfassung |
| This survey takes part in the GEOTREF project (high enthalpy geothermal energy in
fractured reservoirs), supported by the French government program “Investments for the
future”. The program focuses on the exploration of geothermal resource in the Lesser Antilles
volcanic arc. An exclusive license has been issued in the Vieux-Habitants area (Basse-Terre,
Guadeloupe) to carry on the development of high-temperature geothermal energy in this
active volcanic region.
The deep geothermal reservoir on the Basse-Terre island could be characterized in
exhumed paleosystems. The reference paleosystem in the Guadeloupe archipelago is located
in Terre-de-Haut.
Four major fault directions have been highlighted N000-N020, N050-N070, N090-N110
and N130-N140. Field observations emphasize three major cleavage directions overlaying the
fault systems: N035-N060, N080-N110, N145-N165. Volcanic rocks affected by cleavage
display several metamorphic transformation grades. The more transformed calc-alkaline
rocks are located at the intersection of several cleavage directions. Mineralogical
transformations due to metamorphism and surimposed fractures are also responsible for
strong changes of petrophysical properties. In comparison with the reference protolith of
andesitic lava flows outcropping in Vieux-Habitants, which have porosity and permeability
lower than 5 % and 10−15 m2, andesites of Terre-de-Haut have better reservoir properties
with connected porosity and permeability higher than 15 % and 10−14-10−15 m2
respectively.
Thermodynamic modelling based on petrography and chemical composition of the most
transformed rocks highlights a steady state mineral assemblage between 0.25 – 1.5 kbar and
350 – 450 ˚ C. It corresponds to a geothermal gradient higher than 120 to 150˚ C/km. This is
consistent with temperatures measured in Bouillante wells. However, this geothermal
gradient is notably higher to a usual volcanic arc conductive gradient estimated to 70-100˚
C/km. It can be explained by the addition of a convective processes caused by hydrothermal
fluid flows. |
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