Most of the islands in the Caribbean are doted with hydrothermal systems related to
their active volcanoes or recent volcanic complexes. They have been surveyed to
assess their geothermal potential. To date, only the Bouillante field in Guadeloupe,
F.W.I., is currently exploited for electricity generation. It is a conventional high
enthalpy system with reservoir temperature around 250°C. Seven deep wells (350-2,500m
deep) have been drilled and four are producers, feeding the two small plants (4,5 and
11MWe). Permeability is primary controlled by faulting within the basement made of
submarine volcanic formations. The geothermal fluid is a Na-Cl brine with a 20g/l TDS
and has a mixed origin between meteoric water and sea water. A stimulation experiment
based on cold seawater injection was successfully performed in 1998 in order to
improve the permeability of the BO-4 low-producer well.
Two other islands (Dominica, St. Lucia, B.W.I.) are provided with promising high
enthalpy geothermal fields. The Sulphur Springs field in St. Lucia has been explored
in the 1980's.
Two deep exploratory wells have been drilled to 2,200m deep in 1987-88. High
temperature conditions (285°C) but adverse fluid chemistry (low pH, high NCG content)
and low permeability prevent any development until now. Dominica contains at least
two high enthalpy geothermal systems in Wotten Waven and Soufriere areas. No well was
still drilled but fluids geochemistry indicates reservoir temperature conditions
above 200°C.
The island of Martinique, F.W.I., has been explored in the 1970's and in 2000-01 with
4 exploratory wells drilled in the Lamentin area, South of Fort-de-France. Surface
manifestations included hot springs, soil gas anomalies and silica travertine deposits.
Unfortunately, the recorded fluid temperature is only 80-90°C. Two other areas with
surface manifestations were investigated near the Mont Pelée active volcano and near
a 1 My-old volcanic complex in the South-West region. Deep hydrothermal systems with
temperature around 180-200°C are expected from fluid geothermometers but there are
still large uncertainties about their potential, especially about permeability
conditions.
Extension of EGS technologies to the Caribbean geothermal fields could be beneficial
in the light of their high temperature conditions at shallow levels. They could be
used first to enhance permeability conditions for production/reinjection wells.
Others applications could be addressed to the field management. However, the
implementation of EGS methods will have to take into account the island remote
location and related extra costs, and sometimes the limited financial capacity of
local geothermal operators to support them.

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