MAGNETOTELLURIC IMAGING OF GEOTHERMAL ANOMALIES IN THE EASTERN OLKARIA DOMES, KENYA

Olkaria is the most explored volcano along the Kenyan Rift Valley and it is in the advanced stages of development. Despite Olkaria's success as an energy provider, there is continued research into methods to improve the development of the fields. The area, east of the domes only has a single well OW-922 unfortunately, it did not sustain discharge during testing. A combination of 1D Magnetotelluric (MT) and Transient Electromagnetics (TEM) methods were utilized to understand the area resistivity structures. However, there were limitations in mapping the deep-seated structures. A geoscientific study has to be done to gain a deeper understanding of the resistivity structures of the subsurface. Geothermal investigation was carried out using the MT method to identify potential areas and subsurface structural information in the eastern side of Olkaria domes, Kenya. Dimensionality analysis using phase tensor was conducted to determine the presence and dimensions of the underlying structures using 50 MT soundings. MT data analysis was done to derive a dataset suitable for defining the resistivity model of the Earth from the observed MT data. Dimensionality analyses demonstrated that the MT data can be interpreted using two-dimensional approaches, but some localized 3D effects are observed. The inversion of data into resistivity models was performed using Occam 2D. The resultant 2D resistivity models were interpreted to identify the components of the eastern side of the Olkaria domes geothermal system. The two profiles obtained revealed a similar structure which can be construed as a potential pathway of low resistivity used by geothermal fluid to migrate and manifest on the earth’s surface