Evaluation of Kenyan bentonite clay as geothermal well drilling mud

Abstract

The quest for the development of geothermal plants with capacities up to 10,000 MWe in Kenya has recen tly placed greater demand on bentonite clay. Bentonite clay is at present largely imported into the countr y at the great expense of foreign exchange. There is thu s, need to source for bentonite clay locally. In th is study, the suitability of Kenyan bentonite, in its raw for m for possible use in well drilling was evaluated. Selected samples from Isinya, Amboseli and Lewa were charact erized by scanning electron microscopy, energy- dispersive x-ray, x-ray diffraction and x-ray fluor escent to determine the microstructural, elemental, mineralogical and chemical composition respectively . Moreover, rheological analyses were performed on raw samples to evaluate the bentonite clay's suitab ility in geothermal well drilling applications. Res ults revealed that chemical, mineralogical and rheologic al properties of unmodified clays are not adequate for use in drilling application. However, by modificati on of Isinya and Amboseli clays, the composition of calcium may be reduced significantly leading to imp roved flow properties required in drilling mud.