Gichira, J., Noor, Y.
Geothermal Development Company
With an estimated geothermal potential of 10,000 MWe, the Kenyan Rift section of the rift
valley is a beehive of exploration activities. A closer look at Menengai, a new geothermal
project under extensive exploration gives an insight of how to characterize a viable system.
This study involved resistivity and potential field methods mainly gravity. Surface studies done
in Menengai field have indicated a huge geothermal potential and has led to the drilling of
several wells. The purpose of this study was to employ resistivity and gravity methods to
understand the nature of Menengai field by developing resistivity and density structural models
to characterize this geothermal system. The data used was sourced from Geothermal
Development Company (GDC) and subjected to the necessary procedures before developing
final models using WinGLink and, a program by golden software. For resistivity data, the
outliers were removed then the data corrected for static shift followed by joint inversion and
finally run through a 3D code. For gravity data, reduction procedures were done followed by
trend surface analysis to separate regional from residual and finally specific filters applied to
achieve the aim of this study. From this study, 3D resistivity models and gravity structural
models were developed and the information used to characterize Menengai geothermal field as
a high temperature field. Resistivity models were able to identify possible heat sources and
outflow areas while gravity models identified permeability controls for Menengai geothermal
field as follows: caldera rim faults that contribute mostly to deep vertical recharge, NNE-SSW
faults along Solai graben, NNW-SSE faults along Molo axis, the southern fault extending
towards Lake Nakuru and the uplifting dome in the central part of the caldera which enhance
further fracturing within the caldera.
Key words: Geothermal, Resistivity, Potential.