Magnetotelluric Exploration at Tendaho High Temperature Geothermal Field in North East Ethiopia

Abstract

Tendaho is one of the high temperature geothermal areas in Afar depression in north east Ethiopia. A total of 85 MT sites were acquired from Tendaho high temperature field. The main objective of this study is to understand the deep geothermal reservoir not reached by vertical electrical sounding. 2D inversion of MT data along seven profiles was performed in Dubti, Ayrobera and Kurub areas. The 2D inversion of MT data from Tendaho high temperature field revealed three main resistivity structures down to a depth of 10 km: low resistivity surface layer underlain by a resistive layer followed by good conducting structure. The low resistivity surface layer can be interpreted as sediments, lateral flow of geothermal fluids or Zeolite-clay alteration zone. Below the conductive layer, high resistivity is observed, which can be correlated to Afar stratoid basalts or epidote alteration zone .The high resistivity structure can also be associated with the deep reservoir of the geothermal system. The deep highly conductive body is presumably associated with the heat source of the geothermal system. The possible fracture zone inferred in the Afar stratoid basalts may give high temperature and high permeability. The 2D resistivity elevation slices showed possible upflow zone south east of the exploratory wells drilled in Dubti area.