| Title | The Matouba Geothermal Prospect: a Newly-discovered Inferred Geothermal Resource on Guadeloupe Island, French West Indies |
|---|---|
| Authors | Jacques CHARROY, Sébastien HAFFEN, Simon VIARD, Frédéric GÉRARD, GEOTREF Team |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | Matouba, geothermal, resource, assessment, inferred, Guadeloupe, West Indies |
| Abstract | Teranov and its partners in the GEOTREF research consortium have been exploring since 2015 the geothermal prospect of the Vieux-Habitants exploration license area, which encompasses 118km2 on the West Coast of Guadeloupe (French West Indies, see Figure 1), between the Soufrière active volcano and the Bouillante developed geothermal field. This work involved a combination of geological, geochemical, and geophysical surveys with a strong R&D approach combined with a reliance on traditional methods. A complete suite of surface geoscientific surveys was undertaken in an attempt to identify locations suitable for geothermal energy extraction. This included a surface geological reconnaissance, a structural study, the sampling and chemical analysis of known hot and cold springs over the license area, and the interpretation of pre-existing gas sample analyses from fumaroles located on the summit dome of the Soufrière volcano and around its base. Geophysical investigations included the reprocessing of 1970s gravity data with an up-to-date lidar-derived digital elevation model, the acquisition of 103 magnetotelluric (MT) soundings of adequate quality for inversion which were used to produce 1D and 3D resistivity models of the area explored. MT results showed a doming conductive unit interpreted to indicate an underlying geothermal upflow centered close to the steam-heated thermal spring called “Bains de Matoubaâ€. This upflow extends to the west. inside the Vieux-Habitants exploration license area and is clearly separate from that observed below the Soufrière volcanic chimney. The doming MT feature at Matouba aligns with a wide East-West faulted zone interpreted as a structural deformation corridor, and with the “Bains de Matouba†steam-heated feature. This corridor is interpreted to channel an outflow from the inferred reservoir to the west. Although another area of widespread low resistivity was observed on MT contours to the north of the exploration area, the Matouba prospect is considered to be a much more promising exploration target because of the coincidence of positive geophysical, geochemical and structural indices of prospectivity. Temperature estimates of the underlying inferred reservoir were derived indirectly, and therefore come with a relatively low level of confidence: a shallow conductor is present below the Soufrière dome, which extends continuously to the edge of the exploration license area. The Soufrière dome fumaroles are interpreted to be fed by a shallow thermal aquifer with a temperature estimated at 240°C. A continuity of shallow temperature contours matching that observed on resistivity models is postulated, which leads to our estimate of Matouba reservoir temperature of 240°C. A conceptual model of an inferred geothermal resource at Matouba was built to synthesize the geoscientific information gathered to date. An assessment of the inferred Matouba geothermal resource was then produced following the principles of the Australian Resources and Reserves Reporting Code (2nd edition). A high enthalpy geothermal resource is inferred to be located in the Matouba area. A Monte Carlo simulation of the heat stored in the reservoir was run in order to account for uncertainties on key parameter values. On this basis, the inferred Matouba geothermal resource is interpreted to be able to sustain a power production potential of 61MWe (P50) over 30 years. The portion of the inferred resource accessible through wells entirely located within the limits of the Vieux-Habitant license area is interpreted to be able to sustain a power production potential of 38MWe (P50) over 30 years. |