Geophysical mapping of shallow structures controlling geothermal reservoir recharge in Eburru geothermal field, Kenya Rift

Abstract

Eburru Geothermal Field, herein referred to as the study area, that lies in the Kenya rift has been geophysically investigated. The aim of the research was to delineate shallow geological structures beneath Eburru geothermal field with a view to determining their influence to the recharge of Eburru geothermal reservoir. A total of 149 VES data were used to generate both 2D geo-resistivity sections and 3D images. From the research findings, it is envisaged that the study area is underlain by a three layered earth to a depth of about 1000 m. Cross cutting vertical geo-electric features are fault lines connecting shallow aquifers to deep aquifers. Pockets of low resistivity (< 10 Ωm) observed in the study area are possibly due to low temperature secondary minerals of clay such as smectite and illite. On the basis of these findings, it is noted that the geothermal reservoir is recharged through surface infiltration and deep faults. Thus, the deep faults facilitate connection of shallow and deep aquifers. Buried fissure have facilitated accumulation of water behind them and in some cases controlled groundwater flow.