Bouillante geothermal field: mixing and water/rock interaction processes at 250°C.

Bernard Sanjuan (1) , Michel Brach (1) , Eric Lasne (2)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)
2 CFG - Compagnie Française de Géothermie

In the geothermal Bouillante area, electricity is presently produced from well BO-2 only. Following a successful stimulation operation in 1998, a second well BO-4 will be soon connected to the power plant. This paper presents relevant geochemical data obtained for both wells during 1998 and 2000. For some dissolved species, results show discrepancies between surface and down hole samples. In this case, additional information from thermal springs can be very useful to reconstruct the chemical composition of the deep fluid. Despite an high water-rock ratio, the deep NaCl brine (20 g/l) composed of about 58 % seawater and 42 % freshwater reacts with volcanic rocks at about 250°C reaching chemical equilibrium with a mineralogical as-semblage as shown by its composition and by saturation calculations.

Domaines: Géochimie; Milieux et Changements globaux

Bernard Sanjuan, Michel Brach, Eric Lasne. Bouillante geothermal field: mixing and water/rock interaction processes at 250°C.. Water Rock Interaction, WRI-10, International Symposium on Water Rock Interaction, Jun 2001, Villasimius, Italy. pp.911-914. ⟨hal-00772706⟩