| Abstract |
To minimize the dependency on energy imports and to save foreign currency, the use of alternate energy sources using renewable resources has become of great importance. Geothermal development seems to be the long term solution to this problem. In last recent years, the Ecole Supérieure Polytechnique d’Antananarivo evaluated the geothermal resources using geology, geochemical data analyses and geophysical measurements with the aim of elucidating subsurface temperatures and the spatial extent of the geothermal systems. Though limited equipment and after years of research, these published works allowed to identify the geothermal potentialities of the country. The preliminary results of this exploration indicate that more than 120 natural geothermal outcrops are recognized in the country. The distribution of thermal springs, heat flow and the nature of the geothermal reservoirs are controlled by the geological structures. The geothermal areas can be divided in three sections: volcanic terrain, fault zone, and sedimentary basin. Resources and geothermal systems are of two types: volcano-tectonic and tectonic. Subsurface temperatures have been predicted by geothermometry and mixing models. Geothermal systems of medium temperature exist in the recent volcanic area and the possibility of drilling into a medium temperature geothermal reservoir is high, especially in the north and the central part of the country. Subsurface temperatures of about 155°C for the northern zone, 154°C for Itasy and up to 171°C for Antsirabe-Betafo in central part have been predicted by geothermometry and mixing models. The prospects of Itasy and Antsirabe-Betafo are in advanced stages of surface exploration and will soon be subjected to exploratory drilling that will pave the way for a pre-feasibility study. The volumetric and comparative methods are used in order to estimate an average geothermal electricity of its prospect. Currently, geothermal water is used for bathing, swimming, balneology, tourism and washing with little economic return. This paper gives an overview of Madagascar energy sector, known geothermal resources and their potential. Present geothermal utilization and geothermal development update are given. |