| Abstract |
Madagascar intends to reduce its dependence on fossil energy and to mitigate carbon emissions through its energy transition policy by developing alternative and renewable energy from solar, wind, hydro and geothermal energy. This work aims to present an overview of the geothermal potential of one of geothermal regions identified in Madagascar. The North region was investigated for geothermal resource potential, where hot springs with temperature up to 48°C are found at surface. Ambilobe and Ambanja, the two prospects geothermal areas in the North region, consist of normal fault zones with sedimentary-basement contact and graben structures. Quaternary volcanic rocks, mainly basalt, Permian and Triassic sediments dominated by shale and sandstone, which overlie a faulted and fractured Proterozoic metamorphic basement dominantly composed by micashist, gneiss and amphibolite, constitute the main geological units of those areas. A conceptual model of geothermal systems of each prospect area was built, as a first assessment of the geothermal potential in this region, to describe and illustrate essential geological features. Then, hydraulic and thermal properties of rock samples collected from outcrops were measured in laboratory to identify heat transfer processes prevailing in the geothermal systems. The highest values of porosity of 8.7% and 10.7% are found in Permian-Triassic sandstones and in the micashist, respectively. The matrix permeability of sedimentary formations varied around 8.0 mD (7.9×10-15 m2) with an average thermal conductivity around 3.6 W m-1 K-1, while the basement rocks have a permeability ranging between 0.001 mD (9.9×10-16m2) and 10.1 mD (1.0×10-14 m2) and an average thermal conductivity around 2.7 W m-1 K-1. The characteristics of geothermal systems in North of Madagascar share similarities with other geothermal systems in the world that have successfully harnessed resources with low-to moderate enthalpy. Ambilobe shares similarities with geothermal systems in western Great Basin in the Basin Range in America, whereas Ambanja is more comparable to geothermal systems in western Turkey. |