Application of Schlumberger soundings at Eburru, Kenya and TEM and MT methods at Bakki, S-Iceland

Abstract

The 2-D Schlumberger and the combined 1-D TEM/MT sounding interpretations have given results that relate to permeability, temperature, degree of hydrothermal alteration, and geological and structural features of Eburru and Bakki geothermal fields. The 2-D interpretation of Schlumberger sounding data from Eburru, Kenya has identified two anomalous areas of low resistivity (< 10 m) at 1000 m a.s.l. The first anomaly is in the Eburru crater area which is currently under exploratory drilling. The low resistivity seems to define an area of interpolated reservoir temperature of 200 C. The low resistivity above 1800 m a.s.l. is caused by hydrothermal alteration of pyroclastics by acidic steam condensates and lateral outflows mainly to the northwest, northeast and south along faultlines. The low resistivity area has sharp boundaries. Outside this area the resistivity is higher (> 30 m) due to low permeability and temperature which has been confirmed by exploration wells. The second anomaly is found in the Badlands in association with a gravity high and a magnetic low. The two areas are separated by high resistivity and an E-W structural discontinuity. The depth to the bottom of the low resistivity is not defined. The combined interpretation of 1-D TEM and MT sounding data at Bakki and a comparison with well data shows that the surface low resistivity layer ...