Numerical modeling of the geothermal hydrology of the Volcanic Island of Basse-Terre, Guadeloupe

Abstract

This study investigates the thermo-hydraulic implications of three geologic scenarios for characterizing the geothermal hydrology of Basse-Terre Island, Guadeloupe. Despite newly acquired magnetotelluric, petrophysical, and geologic data, flow patterns and heat sources have remained elusive. Our simulations were performed in 2D, on a cross section going from La Soufrière volcano in the south to the operating Bouillante geothermal field near the west coast. Simulation results are compared to geologic constraints such as the temperature profile measured at Bouillante and the timing of volcanic activity in the area, which may be indicative of new heat sources at depth. The simulations indicate that during lateral flow from La Soufrière, geothermal fluids would cool too much to explain the temperature at Bouillante. Two other scenarios were found to explain the current thermal structure of the Bouillante geothermal system: a young (ca. 5000 years) and more local magmatic intrusion at depth, or vertical corridors of enhanced permeability that tap hot and porous formations at a few km depth. Without further geologic evidence, neither of these two scenarios can be preferred. The second magma chamber scenario would indicate a more complex magmatic history of the island than previously established. The study shows that geologically constrained scenarios of regional geothermal hydrology can be meaningfully tested with current numerical simulation techniques, providing further insights for geothermal exploration.