Geophysical Study on Nord Ghoubet Geothermal Prospect, Djibouti
Salahadine MAHAMOUD, Nasradin IBRAHIM and Hassan MAGAREH
As part of the development of renewable energy, especially geothermal energy, a vast program of multidisciplinary studies carried out on the North Ghoubet prospect. This site is located in the central part of the Republic of Djibouti north of the Bay of Ghoubet Al Kharab, between Lake Assal and the Gulf of Tadjourah. The CERD (Center for Research and Studies of Djibouti) has just carried out a prefeasibility study on the geothermal site located north of the screen, which presents tectonic effects of the Assal rift, structures of Makarassou and structures ancient tectonics. This site is never far from the sites of Asal-Fiale and Galé-le-Coma. This site presents the normal NNW-SSE and WNW-ESE faults and the N-S erosion corridors, with Wadi descending in the Goda Mountains (1799m). The purpose of the geophysical survey was to delineate the boundaries of the geothermal reservoir. This site has hydrothermal events such as hot springs and fumaroles on normal faults. Surface and sub-surface surveys have already been carried out in this area in 1979, 1980 and 1982 as part of Geothermal reconnaissance survey by gravimetric, electrical and audio-magnetotelluric (AMT) surveys. In 2010, the geophysical campaign conducted by the CERD team carried out 30 magnetotelluric (TM) and 26 electromagnetic time domain (TDEM) soundings. A map of residual anomalies of Bouguer established by the BRGM (1993) provides information on three negative anomalies. After these geophysical studies, three areas of geothermal interest from about 1000 m have been selected. Different methods in geothermometry indicate a wide range for tank temperatures that are between 100/160 °C and 260/280 °C.These areas are at the top of the horst Moudoud, southeast of the prospect and at the foot of the south-west. A complementary multidisciplinary study (geophysical, geochemical and geological) is planned in February 2019 on this prospect. The objective of this complementary study is initially to densify the number of MT and TDEM stations in the field in order to cover the entire prospect and in a second to consider when interpreting these data an approach multidimensional that better takes into account the geological reality of the mapped basement.
|        Topic: Geophysics||Paper Number: 13129|