| Abstract |
To assess on behalf of GSE (Geological Survey of Ethiopia) the feasibility of development and exploitation of Dubti geothermal resources (Tendaho Graben, Ethiopia) the available documentation was reviewed by ELC Electroconsult and an updated assessment of the project status was elaborated. Such documentation included the results of numerous geoscientific investigations and of five wells drilled in the area to depths included between 460 and 2,200 m, out of which three are productive. The evaluation of the geothermal prospect and in particular of the existence of a deep resource and of a commercially exploitable shallow reservoir was conducted through the following steps: Independent Review of the Scientific Work, Program for Drilling of Geothermal Wells and Technical, Economic and Financial Streamline Feasibility Study. Among the different scenarios, the immediate exploitation of the proven resource pertaining to the shallow reservoir was recommended, through the installation of a geothermoelectric power plant with a capacity of up to 12 MW. The liquid dominated shallow reservoir is encountered at depths in the 220-510 m range, with pressure and temperature close to a Boiling Point for Depth distribution. Different options were analysed as refers to drilling of production wells for the exploitation of the shallow resources. The recommended solution was to make use of the Kremco drilling rig owned by GSE, after an adequate refurbishment. The utilization of the Massarenti drilling rig, owned by GSE too, should be considered as a “mitigation option” in case the Kremco rig is not available for any reason. The level of knowledge of the shallow reservoir is largely sufficient to start the development of the entire project together with the preparation of the procurement process for the power plant and the gathering system. The need of drilling additional production wells closer to the upflow zone, as well as the lack of a numerical model of the reservoir, suggest to postpone the final assessment of the power plant capacity. The analysis of alternative exploitation technologies allowed to select as most suitable, from the technical and economic viewpoints, a single flash condensing power plant. Following such selection, the basic design of the Fluid Collection and reinjection System and of the power plant has been carried out. |