5 Reserve estimates
The investigation indicates that the most important coal-bearing sequences are found within the Upper Cretaceous formation of Yesomma Sandstone. The Jurassic aged coal deposits are very thin while the Tertiary deposits are poor in quality.
The available data on the coal deposits of the Upper Cretaceous is currently inadequate for definitive evaluation of either the quantitative or qualitative factors of the resource. The potentially coal-bearing sequences in the upper part of the Cretaceous sequence are often not exposed for regional investigation due to the thick coverage of Auradu limestone. Both in Hed-Hed and the Guveneh areas, the coal deposits occur 40–50 meters below the base of the Auradu limestone which is highly resistant to erosion and weathering. As a result, the outcrops of coal-bearing beds are only exposed over small distances making it difficult to adequately evaluate their quality and reserves.
Furthermore, open cast mining will probably not be economically feasible due to the high stripping ratio (>10) and thick and hard overburden rocks (Auradu limestone) which will require considerable drilling and blasting prior to excavation. Another major problem for future development of this resource is that the deposits are located hundreds of kilometers from the major cities of the country (such as Hargeisa, Burao, and Berbera) and there is currently no road access to any of the deposits. To reach the Guveneh deposit it currently takes at least a day of off-road driving and trekking on foot from the Las Dureh village.
Therefore, all of the coal deposits which have been investigated are not presently recognized as being a resource or reserve due to their relatively low calorific value, poor quality, high ash and sulphur contents, and difficulties in accessing the deposits. The deposits may still have the potential to provide an important alternative fuel resource in the future. However, further investigation of the coal deposits of Somaliland, including drilling and laboratory analyses particularly of the Upper Cretaceous coal seams, is required to effectively evaluate the quality and resource potential of these deposits.
6 Conclusions
The outcrops and available geological and drilling data show that Somaliland has a high potential for coal deposits. In summary, this study found that:
- Lignitic to sub-bituminous coal deposits of various ages from Jurassic to Oligocene-Miocene have been formed at various locations across the country, including Hed-Hed valley south of Onkhor, Guveneh north of Las Dureh, and Daban Basin southeast of Berbera.
- The Jurassic coal of Gal Hamud has the highest quality with low ash content and high calorific values. However, the coal-bearing horizon is very thin.
- Four seams of varying thickness are recognized in the Hed-Hed area within the Upper Cretaceous Yesomma (Nubian) Sandstone. These seams are lignite to sub-bituminous in rank with calorific value of 4,712 kcal/kg to 5,550 kcal/kg, moisture content of 8% to 17.4%, volatile matter of 33.9% to 38.1%, sulphur content of 0.55% to 0.65% and vitrinite reflectance (%Ro) ranging from 0.38 to 0.44.
- The depositional environment for the formation of the Hed-Hed and Guveneh coal seams was upper delta plain with peat swamps that were not dense enough to develop clean coal beds. Both in Hed-Hed and Guveneh the peat accumulations were not isolated from clastic influx and, as a result, high ash content of impure coals developed.
- Oligocene-Miocene coal deposits of the Daban Basin have lower quality compared to the other deposits. The coal has a high percentage of ash and a relatively low calorific value. The depositional environment for the formation of the seams was that of an estuarine with low acidity and high sulphate content.
- Available geological and drilling data of the coal seams are inadequate to accurately estimate reserves of the deposits. The coal-bearing sequences of Upper Cretaceous are unexposed in many parts of the country and therefore inaccessible for regional investigation.
- Coal deposits preserved in the country have the potential to alleviate the growing shortage of traditional fuels and assist in reducing dependence on imported energy. However, more exploration work and in particular sub-surface drilling is needed, especially in the Cretaceous basins to determine the lateral extent, thickness, and quality of the deposits.
Acknowledgments
I am grateful to Suleiman Weirah, Suleiman Mohamed Ali, and Sahal Adan Mohamed for assisting my fieldwork in Somaliland. I thank Ahmed Behi, Ahmed Ali, and James Small for many valuable discussions. Two anonymous reviewers greatly improved the manuscript.
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