| Abstract |
ReykjavÃk Geothermal (RG) is a development company that has been active in developing geothermal projects in several areas in the world over the past decade. The focus projects of RG have been in Ethiopia where three areas are currently progressing at different stages of development: the Corbetti and the Abaya area, in the Southern Nations, Nationalities, and Peoples Region and the Tulu Moye area, in the Oromia Region. RG signed a PPA with the Ethiopian government for 520 MWe for both the Corbetti and Tulu Moye geothermal prospects. Tulu Moye is in the Main Ethiopian Rift (MER), just 90 km SE of Addis Ababa. And 75 km N of the Aluto Langano geothermal powerplant. The license area includes part of the Gedemsa caldera to the north, Bora-Bericcha rhyolitic formations to the west, a large caldera wall to the east and reaching close Lake Ziway in the south. In the eastern part of the license area, the Wonji Fault Belt (WFB), the most active part of the MER, is present and trends from north to south across the entire concession. This eastern segment is characterized by active faulting, where in the eastern half of the segment there is no volcanic activity present, and on the western half resides a volcanically active feature called the Salen Volcanic Ridge (SVR). Recent formations, such as large obsidian domes as well as lava flows are clearly visible from aerial images, both within the SVR as well as west of the SVR. These formations have not been dated but have been suggested to be as recent as from the late 1800s from historic accounts. In addition, large surface hydrothermal alteration areas are visible and are found on and on a south western segment of a proposed caldera, covering approximately 170 km2 and located in the east of the concession. Geothermal manifestations in the Tulu Moye concession consist mainly of weak steam rising within a hydrothermally altered surface, with temperatures ranging from 37- 95 °C near the surface. These manifestations are aligned to the SVR and the southern segment of the caldera. Locals have used this steam by constructing steam baths on top of the manifestations and use them for bathing; over thirty steam baths have been visited. In 2002 five shallow temperature gradient wells were drilled and all reached more than 90 °C at less than 150 m depth, indicating a shallow boiling system. Gas samples collected in Tulu Moye indicate a reservoir temperature more than 250 °C. An extensive resistivity survey indicates a clay cap in the license area exceeding 200 km2; the full extent of the clay cap yet to be mapped as its boundary exceeds the concession area of interest. Tulu Moye shows the characteristics of a large high-enthalpy geothermal system complete with recent volcanism, extensive surface activity and accompanied with a high estimated reservoir temperature beneath an extensive clay cap, all of which suggests high geothermal potential. |