Updated Conceptual Model and Capacity Estimates for the Greater Olkaria Geothermal System, Kenya

Abstract

The conceptual model of the Greater Olkaria Geothermal System has been revised based on available geological- and geophysical information, temperature- and pressure data, various reservoir testing and monitoring data as well as information on the chemical content of reservoir fluids. Most important are data from about 60 deep wells drilled in the area since 2007. The Olkaria geothermal resource can be split in two; a heavily explored part where extensive drilling has delineated the resource and long-term utilization experience exists and a less explored part where drilling has been limited and mainly indirect indications on an exploitable resource exist. The conceptual model for the former part is quite accurately defined while the model for the latter part is quite speculative. At least three deep magmatic heat sources are assumed in the system with hot water up-flows into the four main well-fields. The resources anticipated in the less explored part require exploration through comprehensive geophysical surveying. The electrical generation capacity of the heavily explored part of KenGen‘s concession area in Olkaria is estimated to be 630 MWe or more based on a volumetric resource assessment, lumped parameter pressure response modelling and detailed numerical modelling (see a separate paper). This includes 150 MWe already installed and 280 MWe under construction. The results of the three different assessment methods are quite comparable, which adds confidence to the results. The electrical generation capacity of the less explored part is estimated to be about 300 MWe based on a volumetric assessment, an estimate that needs to be confirmed through comprehensive exploration and drilling.