BRGM – Development of the Bouillante high-temperature geothermal field (Guadeloupe, French West Indies): a pioneer site for the Caribbean region

B. Sanjuan (BRGM – Geothermal Division, Géoressource Department)

In a context of energy transition and steady increase of the population and of energy demand in the Caribbean volcanic islands, the development of geothermal energy can provide base load and competitive electricity in territories faced to the fragility of their energy systems and of their environment. But paradoxically, the Bouillante geothermal plant is the only installed capacity in this area (15 MWe, presently), located in a high-temperature (260°C) geothermal field, along the coast of western Guadeloupe (fig. 1), since almost 40 years. Exploited by the Geothermie Bouillante Company (GB), since 1995, it presently produces about 110 GWh of electricity from two units, supplied with steam by two deep wells (about 1000 m). This production covers 6 to 7% of the demand of the island. A partial underground fluid reinjection is operational, since 2015.

Exploration by BRGM and EURAFREP began in the 1960s. Since then, the Bouillante geothermal field has been a playing field for research, development and innovation of BRGM, which has developed methods and tools to be applied to Bouillante, but also to other overseas territories and abroad. Most of these activities are co-funded by ADEME (Agency of the Ecological Transition) and some other by European Union. They are focussed on developing and improving:

• the exploration methods necessary to better characterize and understand the geothermal resources, and estimate the potential of a high-enthalpy geothermal area such as Bouillante;
• the methods of monitoring and exploitation management of this type of field, in order to optimize the electricity production, and secure the environmental impact of the geothermal exploitation.

Among the methods of the first axis, the development of prospecting tools so as to reduce the geological hazards and risks when drilling the very costly wells is also another main objective. Bouillante is used as a pilot site by BRGM to test geological, geochemical and geophysical methods for geothermal exploration and identify those that are the most effective for the overseas specificities. So, several works of bathymetric measurements, structural geology, mineralogical characterization and datations of volcanic rocks and hydrothermal alterations were developed between 1996 and 2013. Different geophysical methods as gravity, magnetism, electro-magnetism and seismology are also tested. Geochemistry methods, especially in terms of fluid origin, water-rock interaction and estimation of reservoir temperatures, using fluid samples collected from production wells and neighboring thermal manifestations, are developed. Relative to the second axis, one can mention the successful thermal stimulation of an old poorly productive well in 1998 (unique in the world at this time), the realization of chemical tracer tests and works of reservoir and well modelling (3D-reservoir geological model; thermal, hydrodynamic, and chemical numerical simulations). The Bouillante field is also one of the rare geothermal site where numerous monitoring techniques (surface soil thermometry, fluid geochemistry, gravity, broadband seismology, INSAR technology) have been used, in order to control the impact of the geothermal exploitation on the evolution of the production and the immediate environment of the power plant. These techniques were implemented and developed by BRGM between 1998 and 2016.  

Thanks to all these activities, the production capacity of the Bouillante power plant could be increased from 4 to 15 MWe, in 2005. A 50 year-concession, covering a large part of the Bouillante commune territory, and taking into account the knowledge and the field understanding acquired by BRGM, was granted to GB, in 2009. Additional field development and production increase are clearly possible, notably in promising areas such as the northern part of the Bouillante Bay (Pointe à Lézard) and the south of Bouillante (Anse Thomas), where submarine and terrestrial thermal springs with contributions of a geothermal fluid similar to that analysed in the geothermal wells, were identified in these fractured areas (fig. 2). The exploitation and reinjection conditions of the Bouillante reservoir could be substantially improved. BRGM has been also able to apply a part of this expertise in the Martinique and Dominica islands (but other Caribbean islands could be also beneficiaries), in which no power plant exist for the moment, but where several potential geothermal areas have been identified for well drilling.

The activities carried out between 1996 and 2020 by BRGM have generated about 20 international scientific papers, some sixty technical reports and several popular articles. They were presented in about 60 international congresses and conferences. Five PhD thesis (Antilles and Poitiers Universities) and some twenty Master’s training reports were also carried out.