| Abstract |
The Greater Olkaria Geothermal Field is in the southern part of the Kenyan rift, south of Lake Naivasha, approximately 120 km northwest of Nairobi. Exploration for geothermal resources in Kenya started in 1950’s with mainly geological investigations in the region between Olkaria and Lake Bogoria in the north rift. In 1970’s, exploration was concentrated in Olkaria and by 1976, six deep wells had been drilled. After evaluation of these initial wells, development was found to be feasible. Utilization of the geothermal resource began in 1981 when the first 15 MWe generating unit was commissioned by KenGen at Olkaria I power plant in Olkaria East. Thereafter, unit 2 and 3, each 15 MWe, were commissioned in 1982 and 1985, respectively. Olkaria II power plant, in Olkaria Northeast, also owned by KenGen, was commissioned in 2003 with an installed capacity of 70 MWe. Additional 35 MWe unit was added to this plant in May 2010, bringing the total installation to 105 MWe. Olkaria III power plant, owned and operated by an Independent Power Producer (IPP), Orpower4 Inc, was commissioned in Olkaria West in 2000 with initial capacity of 13 MWe and currently generates 134 MWe. Between 2014 and 2015 KenGen commissioned additional 280 MWe in Olkaria Domes and Olkaria East. A Pilot Wellhead plant was installed in Olkaria East in 2012 with a capacity of 5.5 MWe. Following success of the Pilot plant, a total of 15 wellhead plants have been installed in Olkaria, with 81.1MWe generation capacity. The total power generation in the KenGen’s concession area of the Greater Olkaria Geothermal Field now stands at 511.1MWe. Moderate pressure drawdowns have been observed in the field during exploitation. The representative pressure drawdown observed for Olkaria East is ~ 12 bars, Olkaria Northeast ~ 13 bars during the thirteen years of operation of the Olkaria II plant, which is an equivalent of average annual pressure drawdown rate of 1 bar/year. The rate of pressure decline for the Olkaria Domes is ~1.2 bar/year. Re-injection has helped to minimize the rate of pressure decline. Currently the total mass produced in the KenGen’s concession area is ~5600 t/hr and ~50% of which is reinjected. The general trend indicates a rise in the Cl content for Olkaria East Production Field and a decline for Olkaria North East Production Field. |