Mineral Resources Potential - Geothermal Resources

222 Mind Resources Potential of Ethiopia
oxbow lakes and muskegs. Generally, oil shales are considered to
Ix formed by accumulation of algai debris.
Oil can be extracted from oil shale, but they must be heated
to high enough temperatures to drive the oil out. Since this process
quires a lot of energy, exploitation of oil shale is not currently
cost-effective, but may become so as other sources of petroleum
become depleted. Known deposits of oil shale are extensive,
Unlike coal, oil shale does not necessarily require low mineral and
ash content, as it is not used for burning, and mineral waste in oil
liquefaction plants is easier to deal with. Eventually, and usually
due to the initial onset of orogeny or other tectonic events, the
algal swamp-forming environment is disrupted and oil shale
accun~ulation
ceases. Oil shale is known as 'rock that bums'.
Oil shale occurrenm in Ethiopia
Oil shale is said to occur in the south western P h u of the
a country and between Lake Ziway and Lake Abyiata in the valleys
of the Bulbul River and its tributaries. The fluvid-lacustrine oil
shale bearing formations of Delbi, Mefeso, Lalo-Sapo, Solo,
Soyoma, and Mojo-Anchema are an Inter-Trappean continental
sedimentadon on the south western Plateau of Ethiopia. The
deposits occur intercalated within Cenozoic volcanics. The oil
shale is characterized by high ash contents, low calorific value and
low fixed carbon. The Pelbi oil shale has a fixed carbon ranging
from 27.6%83,0% and a calorific value r&iging from 58 1-6,165
kcalkg. Recent drillidg data proved the presence of 1W120
million tons of oil shale deposits at Delbi (Wolela, 199 1 ; 1995).
No details are known for the Bulbul River deposits.
7.2 Geothermal raources
Geothermal energy resources result from complex geologic
processes that lead to heat concentration at accessible depths. The
different forms of gmthermd energy resources-hydmthed, hot