MAGNETOTELLURIC AND GRAVITY DATA ANALYSIS OF THE OLKARIA GEOTHERMAL FIELD, KENYAN RIFT: PRELIMINARY RESULTS

Olkaria is a large volcanic complex with no visible caldera within the Kenyan Rift, East Africa. The volcanic complex has successfully been exploited for geothermal power since 1981 currently producing over 250 Mwe. In order to investigate the source of the geothermal system, magnetotelluric (MT) and gravity data have been collected during the past 10 years in order to image the magma bodies and crustal structure that is associated with the geothermal system. The MT data analysis will include determining the data dimensionality, and inverting the data for 2D and 3D electrically conductivity structure. These MT models will be compared with 3D gravity inverse models to draw a comparison of these methods in determining the presence of the hot magma intrusives and the electrically conductive zones in the case of the geothermal reservoir. The models will be used to estimate future development of the field, as the field continues to be exploited for geothermal energy. It is estimated the field has a potential to produce about 2000Mwe. The gravity data and the subsequent analysis (including wavelength filtering and derivative analyzes) will serve as a baseline in future to monitor any changes in reservoir geometry with time. These preliminary models will determine where to collect additional MT, gravity and magnetic data in order to fully investigate the geothermal potential at Olkaria.