The bouillante geothermal power-plant, guadeloupe

Summary Studies on the mechanical behaviour of rocks, including volcanic rocks, usually seek for unaltered and simple material: rocks without macroscopic defects. However, volcanic rocks are often naturally altered due to the circulation of hydrothermal fluids. This alteration may influence mechanical and physical properties. Here, we study the effect of hydrothermal alteration on the elasticity and failure properties of andesite. A homogeneous block of natural andesite was retrieved from a quarry. Three samples were first heat-treated and then artificially altered at different temperatures by soaking them in a brine for one month at a pressure of 20 MPa and temperatures of 80○C, 180○C and 280○C. Heat-treated unaltered and altered samples were hydrostatically loaded up to 50 MPa and unloaded, while strains and elastic wave velocities were recorded. Samples were also triaxially deformed to failure at a constant strain rate and a confining pressure of 15 MPa. At ambient pressure, increased alteration temperature resulted in increased wave propagation velocity, thus increased dynamic elastic moduli. During hydrostatic loading, volumetric deformation at a given effective pressure decreased with alteration temperature denoting increased static elastic moduli. During triaxial loading, the degree of alteration decreased elastic compaction and peak stress at failure. These observations are interpreted as the result of micro-cracks in-filling by alteration minerals, and in particular smectite, a swelling-clay mineral with a low friction coefficient. The mechanical behaviour of a volcanic rock subjected to triaxial loading was modelled with a damage model based on crack propagation from pre-existing flaws. A decreasing friction coefficient within the flanks of the cracks leads to a decrease of the peak stress and explains the experimental observations.

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“…• C recorded at Bouillante geothermal field in Guadeloupe (Jaud & Lamethe 1985;Traineau et al 1997).…”

Section: Starting Material Heat-treatment and Artificial Alterationmentioning

confidence: 99%

Influence of hydrothermal alteration on the elastic behaviour and failure of heat-treated andesite from Guadeloupe

Nicolas

Levy

Sissmann

et al. 2020

Geophysical Journal International

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“…The water flowing through the geothermal aquifer has a homogeneous composition at the spatial scale of the Bouillante region and the reservoir represents a total volume larger than 30 million m 3 with a temperature of 250-260°C (Mas et al 2006). In 1986, a geothermal plant without reinjection started producing electricity by exploiting water coming from a 340 m deep well (Jaud & Lamethe 1985). Additional deeper wells (1000-1200 m) are now used to reach a power output of 16 MWe (Mas et al 2006).…”

Section: Study Areamentioning

confidence: 99%

Influences of geothermal sulfur bacteria on a tropical coastal food web

Pascal¹,

Dubois²,

Goffette³

et al. 2017

Mar. Ecol. Prog. Ser.

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The activity of the geothermal plant at Bouillante in Guadeloupe (French West Indies) releases thioautotrophic bacteria into the coastal environment. Fish counts reveal that fish abundance increases with higher availability of this bacterial resource. In order to evaluate the trophic role of these bacteria, isotopic compositions (C, N, S) of potential consumers were evaluated on transects at increasing distance from the source of bacteria. The 3 mobile fish species examined (Abudefduf saxatilis, Acanthurus bahianus, and Stegastes partitus) ingested and assimilated chemosynthetic bacteria. Similarly, the isotopic composition of the mobile sea urchin Diadema antillarum was different close to the discharge channel, suggesting a diet mainly composed of sulfur bacteria. In contrast, endofauna sampled from the nematode community did not show a diet influence by chemosynthetic bacteria. A broad variety of epifaunal organisms with passive and active suspension-feeding activities were also investigated, including sponges (Aplysina fistularis and Iotrochota birotulata), barnacles (Balanus sp.), bivalve molluscs (Spondylus tenuis) and cnidarians (Pseudopterogorgia sp.), but no strong evidence for sulfur bacteria contributions were determined in the diets of any of these organisms. This was also true for the omnivorous predator annelid Hermodice carunculata. In this coastal oligotrophic environment, only certain opportunistic species seem to benefit from the emergence of a new food item such as chemosynthetic bacteria.

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“…Bien que les études de reconnaissances aient indiqué qu'en France il n'y a pas de contextes géologiques favorables pour le développement de la géothermie haute enthalpie, dans les départements d'outre-mer, il y a des conditions plus propices pour l'exploitation de ce type de ressources. La première centrale géothermique française a en fait été construite sur l'île de Guadeloupe et a commencé sa production en 1986 [JAUD et LAMETHE, 1985]. Dans les sections qui suivent, les caractéristiques principales des sites de Soultz-sous-Forêts (Alsace) et de Bouillante (Guadeloupe) sont résumées pour donner un exemple d'exploitation de ressources géothermiques EGS et de haute enthalpie.…”

Section: Géothermie Pour La Production D'électricité En Franceunclassified

“…La Guadeloupe se situe au voisinage de la zone de subduction entre la plaque de l'Amérique du Nord et la plaque des Caraïbes, où la première descend sous la deuxième à une vitesse moyenne de 2 cm/an [GAILLER et al, 2014]. Il s'agit d'une région avec un important risque sismique, en plus d'être soumise aux cyclones tropicaux, généralement entre juillet et octobre [JAUD et LAMETHE, 1985].…”

Section: Centrale Géothermique De Bouillante (Guadeloupe)unclassified