九大地熱・火山研究報告第 11 号 (2002) 12-15 頁

GEOTHERMAL EXPLORATION IN ETHIOPIA, COUNTRY REPORT
Tadesse Mamo

ABSTRACT
Geothermal exploration started in Ethiopia in 1969. The study covered 150,000 km2 in the Ethiopian Rift valley
and identified over 500 thermal features. Semi-detailed scientific study including geology, geochemistry andgeophysics has been carried out in most parts of the Afar Rift and the Main Ethiopian Rift. Further more, adetailed geoscientific study has been conducted in Aluto - Langano, Tendaho, Corbetti, Abaya, Gedemsa and Tulu
Moye areas and the out come of the study indicate a promising result for further feasibility study. Based on theprevailing results follow up feasibility study was carried out in Aluto - Langano Geothermal field and indicateda potential of 30 MWe. Currently a 7.5 MWe pilot plant has been installed and connected to the national grid. InTendaho geothermal field (Afar Rift) a follow up feasibility study is underway and the present status shows thatthe field has a potential of 20 MWe.
1. INTRODUCTION

Based on the encouraging results of the 1969 surveya detailed geoscientific study was conducted in AlutoLangano, Corbetti and Abaya geothermal prospects
jointly by Ethiopian Government and UNDP.

1.1 Background
Geothermal exploration started in Ethiopia in 1969
jointly by the Ethiopian Government and the United
Nations Development Program (UNDP). The main
purpose of the work was to study the geology,
geochemistry and hydrology of hot springs of the East
African Rift System within Ethiopia. The Ethiopian
Rift Valley extends from the Ethio - Kenyan borderin the south and running in NNE direction to the Red
Sea to the north. The study covered 150,000 km 2
area of the Ethiopian Rift including Afar Rift and theMain Ethiopian Rift (MER) and identified more than
500 hydrothermal features (Fig. 1). The study has
confirmed that Ethiopia has a potential of about 700
MWe of Geothermal resources in the Ethiopian Rift
Valley.

2.1.1. Aluto-Langano Geothermal Field
This field has been intensively explored. The
exploration work included geological, geochemicaland geophysical surveys. Following these detailed
investigations, eight deep exploratory wells weredrilled in the area between 1981 to 1985. Five of thedrilled wells turned out to be productive.
The productive wells have proved a geothermal
reservoir having fluids with high enthalpy (1500-1900kj/kg) and temperature of 335 °C. Feasibility study
shows the Aluto-Langano geothermal field is capableof generating 30 MWe for 30 years. Currently a 7.5
MWe pilot geothermal plant has been constructed.
The plant is a binary type supplied with steam
and brine from four productive wells. One of theexploratory wells is serving as reinjection well. The
plant is connected to the national grid and supplyelectricity. There is also a continuous program toupgrade the capacity to 30 MWe by drilling additionalwells.

The Ethiopia Government encouraged furtherexploration works. Geothermal exploration studies
were conducted at different levels and their status will
be discussed as follow:
2. GEOTHERMAL ACTIVITY IN ETHIOPIA

2.1. Main Ethiopian Rift
Geothermal Division, Ethiopian Geothermal Survey P.O. Box 40069, Addis Ababa, ETHIOPIA

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GEOTHERMAL EXPLORATION IN ETHIOPIA, COUNTRY REPORT

temperature 241°
C. The third well (TD-3) turned out
to be non productive.

2.1.2. Corbetti Geothermal Prospect
The Corbetti prospect area is one of the mostpromising geothermal field. A detailed geoscientificinvestigation including geology, geochemistry
and geophysics was carried out. Eight shallow
temperature gradient holes were drilled. The resultsof the temperature gradient wells survey indicate an
encouraging result for the drilling of deep exploratory
geothermal wells.

Based on the results of the three deep wells thepermeable zone is observed at shallow level (250 350m). Therefore, three additional shallow wells weredrilled (TD-4, TD-5 and TD-6) between 1994 and1998. Feasibility study was carried out and the results
have indicated the presence of a shallow reservoir.
Currently, the productive wells could supply enoughsteam to operate a pilot power plant of about 5 MWe.
In addition the study has estimated a total potential of
20 MWe.

2.1.3. Abaya Geothermal Prospect
Abaya prospect has been well studied and has lots ofhydrothermal manifestations. A detailed geological(1:20,000) and geochemical investigations werecarried out. Currently a detailed geophysical survey is
being conducted in the area. The present level of study
proves that this field is a promising area for furtherinvestigation.

2.2.2. Southern Afar Area
In the Southern Afar area a coordinated study wascarried out as a project by Electroconsult (ELC)
in association with Geothermica Italian and theEthiopian Institute of Geological Surveys in the years
1985 - 1987. The project mainly concentrated on areconnaissance study of the geothermal sites in theSouthern Afar region and parts of the northern MER.
The areas included in the study were Gedemsa, Tulu
Moye, Kone, Dofan, Fantale, Meteka, Danab, Teo andAbhe geothermal prospects.

2.2. Afar Rift Valley
The Afar rift has been divided into Northern andSouthern Afar Rift areas.
2.2.1. Northern Afar Area
2.2.1.1. Dallol Geothermal Prospect
The prospect area is located in the Danakil
Depression. This area has been well studied during
the 1969 regional survey and it has a good geothermal
potential. Regional geological and geophysicalsurveys had been conducted and there is a future plan
to conduct more detailed geoscientific study.

Based on the result of the survey and socio economic aspect four of the prospect areas namely
Dofan, Fantale, Gedemsa and Tulu Moye areas wereselected for further geoscientific investigations.
Gedemsa prospect was given priority and two
shallow temperature gradient wells were drilled
and encountered cold aquifer. Recently a detailed
geological (1:20,000) and geophysical investigation
has been carried out in Tulu Moye area. Five shallow
temperature gradient holes have been drilled. The
results have confirmed that the Tulu Moye area isa promising field. There are also plans to do more
geoscientific study in Fantale and Dofan geothermal
prospect areas in the coming few years (couple ofyears).

2.2.1.2. Tendaho Geothermal Prospect
Tendaho geothermal prospect is located in the Afar
Depression which is a crossing point of three rifts,
two oceanic (Red Sea and Gulf of Aden Rift) and one
continental (East African Rift). This prospect has been
well studied and eight temperature gradient wells weredrilled by Aquater in 1979.

3. CONCLUSIONS

Prefeasibility study and deep drilling activities werecarried out by Aquater. The drilling has been carriedout jointly by the Ethiopian government and thetechnical cooperation of the Italian Government.
Three deep exploratory wells (TD-1, TD-2 and TD- 3) have been drilled from 1993 to 1994 TD-1
has low permeability and a fluid with maximum
temperature 277°
C. The second well (TD-2) has better
permeability and a water dominated reservoir having

The Ethiopian Rift Valley has a large potential ofgeothermal energy. Ethiopia could generate about
700 MWe using geothermal resources. The existenceof this indigenous energy will satisfy the energy
demand of the country. Aluto-Langano and Tendaho
geothermal fields will be fully operational in the near
future. There is also a plan to do detailed geoscientific13

Tadesse Mamo

investigations for different geothermal prospects.

Ethiopian Rift System, Milano, Italy.

Due to the finance limitation as indicated above thestudies have been conducted jointly by the assistanceof Ethiopian Government and others. Therefore, future
development should focus by attracting donating
governments, organizations and interested investors toparticipate.

Electroconsult (ELC) (1986): Exploration of Aluto-Langano Geothermal Resources, feasibility report,Geothermal Exploration Project, Ethiopian Institute ofGeological Surveys.
Meseret Teklemariam, Kibret Beyene, Yiheyis
Amdeberham and Zewdie Gebregziabher (2000):
Geothermal Development in Ethiopia. Proceedings
World Geothermal Congress 2000, Kyushu-Tohuku,
pg. 475-480.

REFERENCES

Aquater (1996): Tendaho Geothermal Project final
report, Ethiopian Institute of Geological Surveys,Ethiopia.

UNDP (1973): Geology, Geochemistry and Hydrologyof hot springs of the East African Rift System within
Ethiopia, pp 1-285.

Electroconsult (ELC) (1987): Geothermal
Reconnaissance study of selected sites of the14GEOTHERMAL EXPLORATION IN ETHIOPIA, COUNTRY REPORTFig. 1 Location map of the Ethiopian rift valley and the Afar depression showing the explored and geothermal
prospective areas.

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