| Abstract |
The surface investigations of the geothermal resources of Rwanda have been carried out along approximately the 30 last years. The investigations were carried out in two potential prospects which are: the young volcanic lava flows of the Virunga massif which are hosting active volcanoes in its western limb in the Democratic Republic of Congo (Nyiragongo and Nyamuragira volcanoes) and the Upper-Tertiary volcanic field of the Bugarama graben in the South-western part of Rwanda. In both domains, the geothermal manifestations are mainly hot springs, warm springs, gas-rich mineralized springs and travertine either along North-South faulted zones of the Virunga area or in the Bugarama graben. The Virunga geothermal domain was investigated in details and two exploration wells (of the three planned) were drilled. The Bugarama, Gisenyi and Kinigi prospects did not go beyond the reconnaissance phase. Sampling of cold waters, hot waters, soil gas, gasses and rock samples for their chemical analyses and interpretations, geophysical measurements using TEM, MT, passive seismicity etc. and finally the remote sensing-based geological investigations were used for the reconnaissance survey. The key outcome of these researches was that a geothermal resource may exist within the Virunga Massif and/or surroundings. A cross-check of different lithological units, tectonic features and different cones/craters was conducted from October 29th to November, 7th, 2012. The geological and geothermal survey carried out in the Karisimbi area consisted of detailed mapping. This was done stepwise with an understanding and a description of rock units, the structural features of the study area, the geothermal alterations and the relationship between them. Additionally to that, the first exploration well, KW01, was drilled from mid-July 2013 to December 2013. Moreover, the exploration drilling of KW02 started on 14/12/2013. The history of the exploration drilling, challenges and results are summarized in the present work. The gained data will serve for the improvement of the geological conceptual model in the Virunga area and specifically in the Karisimbi prospect. |