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| Titel |
Multidisciplinary exploratory study of a geothermal resource in the active
volcanic arc of Basse-Terre (Guadeloupe, Lesser Antilles) |
| VerfasserIn |
Vivien Navelot, Alexiane Favier, Yves Geraud, Marc Diraison, Michel Corsini, Chrystèle Verati, Jean-Marc Lardeaux, 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 |
250153809
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| Publikation (Nr.) |
 EGU/EGU2017-18832.pdf |
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| Zusammenfassung |
| The GEOTREF project (high enthalpy geothermal energy in fractured reservoirs), supported
by the French government program, “Investissements d’avenir” develops a sustainable
geothermal resource in the Vieux Habitants area, 8-km south of the currently exploited
Bouillante geothermal field.
The Basse Terre Island is a recent volcanic arc (< 3 Myr) belonging to the Lesser Antilles
subduction zone. It is composed of arc typical calc-alkaline volcanic rocks. Outcrops of the
studied area consist either of andesitic lava flows, volcanic sedimentary facies or dikes. Field
studies allow to propose a structural framework and highlight three major directions N000˚
E, N050˚ E and N090˚ E, which are consistent with the regional tectonic trends of
the arc. Petrographical and petrophysical studies displayed that the major part
of outcropping facies in the Vieux-Habitants area are not altered. Andesitic lava
flows have poor reservoir properties with porosity and permeability lower than
5 % and 10−15m2 respectively. These results are in contrast with measurements
performed in volcano-sedimentary rocks, which have heterogeneous petrophysical
properties ranging from 15 to 50 % for porosity and from 10−15to 10−9m2 for
permeability. Such surface data would probably change and decrease when depth
increases.
As there is a lack of underground data under the Vieux-Habitants area (wireline, drill
core), exhumated rocks outcropping in the northern part of Basse-Terre Island (Basal
Complex) have been studied. Such rocks have been identified in the Basal Complex (2.5 - 3
Myr) located in the northern part of the Basse-Terre Island. Previous works have
demonstrated a 1000 m/Myr erosional rate, which corresponds at least to a 2 - 3 km
exhumation.
The petrography study of the Basal Complex reveals sub-greenschist type mineralogical
transformations (chlorite, white mica, quartz...) changing the andesitic protolith in a
meta-andesite. This metamorphism forms cleavage plans thanks to a pressure-solution
mechanism. Mineralogical transformations associated with these cleavage planes have an
impact on petrophysical properties. The solid phase density and porosity decrease. An
anisotropy of permeability develops due to cleavage plans. Thermodynamics modelling based
on the rock chemical composition and petrography observations emphasizes a steady-state
mineral assemblage between 1.5 - 2 kbar and 280 - 320˚ C. This is consistent with
an in situ measured volcanic arc conductive geothermal gradient of 70 ˚ C/km. |
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