Interpretation of recent temperature and pressure data and updated conceptual model of the Greater Olkaria geothermal system, Kenya

Abstract

Optimal development and utilisation of geothermal resources is dependent on the understanding of their size and nature, both in the natural undisturbed state as well as the dynamic response as a result of utilisation, hence the need to develop a conceptual model. The conceptual model is the main input for the complex field numerical modelling for resource estimates and field development plans. The temperature and pressure models are used as the basis for geothermal field concept development as well as geothermal well discharge characteristics such as enthalpy, mass flow and chemistry. The geology, geochemistry, geophysical information, surface geology and borehole geology play a significant role in understanding the heat source, the permeability, flow patterns and the origin of hot and cold recharge of a geothermal system.

The Olkaria Conceptual model has been updated several times, since the first simple one was presented by Sweco and Virkir in 1976, as new data was acquired. The present model was presented by the consortium of Mannvit/ÍSOR/Vatnaskil/Verkís during the field optimisation study in 2012. This report presents the updated temperature and pressure model of the Greater Olkaria geothermal system, based on newly acquired temperature and pressure data through ongoing drilling operations in the field. The perceived change in the conceptual model of the field as result of this new data is also pointed out and recommendations made on further drilling sites to give a better understanding of the Olkaria geothermal resource.