Geology, hydrothermal alteration and fluid inclusion studies of Olkaria Domes geothermal field, Kenya

Abstract

Three geothermal exploration wells OW-901, OW-902 and OW-903 were drilled in Olkaria Domes field to evaluate its geothermal potential. The three wells were drilled to a depth of 2200 m and all encountered a high temperature system and discharged on test. The highest recorded measured temperatures in the wells are; 342°C at -290 masl, 248°C at 207 masl and 341°C at -107 masl for wells OW-901, OW-902 and OW-903 m respectively. Rocks encountered in the wells include pyroclastics, rhyolite, tuff, trachyte, basalt and minor dolerite and microsyenite intrusives. Fractures, vesicles, spaces between breccia fragments, glassy rocks and primary minerals exhibit little or no hydrothermal alteration in the upper parts of the wells with mainly silica, calcite, zeolites, phyllosilicates, oxides and sulphides being the alteration minerals present. In the deeper parts of the wells, however, hydrothermal alteration to ranged from high to extensive...