Federal Institute for Geothermal Development Kenya Electricity Ministry of Energy, African Union Geosciences and Company, Kenya Generating Company Kenya Natural Resources, Germany A Field Guide to the Greater Olkaria Geothermal area for the Regional Geothermal Stakeholders’ th th Workshop 15 -17 March 2010 By John Lagat, Geothermal Development Company Ltd, P. O. Box 100746-00100, Nairobi. Tel: +254 20 242 751619, +254 710 711722 FIELD ITINERARY TIME ACTIVITY 07:00 hrs Delegates leave Nairobi Sarova Panafric Hotel 08:00-08:30 hrs STOP 1: Great Rift Valley View point 10:00-10:30 hrs STOP 2: Olkaria II - Tea and refreshments 10:30-11:00 hrs Tour of Olkaria II power plant 11:00-12:00 hrs STOP 3: Oserian greenhouse tour 12:00-13:00 hrs STOP 4: Rig and a discharging well 13:30-14:30 hrs Lunch Break 14:30-15:00 hrs STOP 5: Maasai Cultural Center 15:00 hrs Departure through Elsa gate (Site seeing) 17:00 hrs Arrival at Nairobi, Sarova Panafric Hotel 2 08.00-08.30 hrs STOP 1: THE GREAT RIFT VALLEY VIEW POINT View the Great Rift Valley, Mt. Longonot, Mt. Suswa and Mt. Margaret LONGONOT Longonot volcano consist of a cone which rises 1000 m above the rift floor and has a gentle slope to the south. Arcuate ridges extend around the western and the southern side of the cone and are topographic expression of a caldera rim. The main events of the volcanological history of Longonot volcano are outlined below: Building of a ‘shield’. Caldera formation. Building of pyroclastic and lava cones. Formation of the summit crater. Flank and crater floor eruptions. The age of the last eruptions at the northern flank and the caldera floor is about 200 years BP. Surface studies were carried out in Longonot in 1998 and from the Geoscientific studies the prospect has a potential of 650 MWe. Figure 1: Geological map of Longonot prospect. Plate 1: Longonot crater Suswa is the southernmost of a series of Quaternary caldera volcanoes in the Kenya rift. SUSWA The volcano has two nested calderas: outer and inner with diameters of 10 and 4 km, respectively (see picture). Volcanism at Suswa that comprised trachytes and phonolites started about late Pleistocene and continued to less than 1,000 years ago (Omenda, 1997). Results from detailed surface studies suggest reservoir temperatures of 250oC based on gas geothermometry. Seismic and gravity studies show that the heat source under the caldera is at about 6-8 km deep with a NE-SW bias. The estimated potential of the prospect is >600 Plate 2: Aerial view of Suswa caldera MWe. 3 Figure 2: The excursion route around the Greater Olkaria geothermal field 4 THE GREATER OLKARIA GEOTHERMAL FIELD Geology The Olkaria geothermal area is located within the Greater Olkaria Volcanic Complex which consists of a series of lava domes/flows and ashes; the youngest (Ololbutot) of which was dated at 180 50 yr BP (Clarke et al., 1990). It is believed that the intrusive portions of these magmas are responsible for the high heatflow in the area. Rhyolitic volcanism, which is so prominent in the Olkaria area, commenced about 400,000 years ago. Olkaria Hill is the main landmark in the area and the fields are named according to their position with respect to the Hill. Plate 3: View of Olkaria Hill from the East. Explosion craters and rhyolite dome are visible in the photo. Geothermal Potential To date, over 120 geothermal wells have been drilled in Olkaria. The current installed power potential at Olkaria stands at 174 MWe. However, it is estimated that the geothermal potential of the entire area could exceed 800 MWe. Olkaria geothermal area has been divided into seven development sectors out of which only three are committed to development. The sectors (fields) are Olkaria East, Olkaria North East, Olkaria South West, Olkaria Central, Olkaria North West, Olkaria South East and Figure 3: Geological map of Olkaria Geother- Olkaria Domes. The fields are named in respect mal Area. to the Olkaria Hill. GREATER OLKARIA EXCURSION PROGRAMME 10:00-10:30 hrs STOP 2: OLKARIA II POWER PLANT 10:30-11:30 Tour of Olkaria II Power plant Thirty three wells were drilled in Olkaria North East field and twenty-two wells are connected to Olkaria II power station. Most of the wells produce from the Olkaria fault that runs ENE-WSW. All the discharge brine is being re-injected hot at the borders of the field. The power plant was commissioned in 2003. An additional 35 MWe unit is being constructed and will be commissioned in 2010. 5 Plate 4: Photo showing Olkaria II power plant 11:00-12:00 hrs STOP 3: OSERIAN GREENHOUSE PROJECT 11:10-12:00 Guided tour of Oserian Greenhouse Project The primary aim of Oserian’s greenhouse heating is to control night-time (and wet season) humidity levels in the greenhouses, thereby alleviating fungal disease. The project utilizes steam from well OW-101, which is one of the early exploration wells in that sector of the field. Tests have shown the well to have a typical average output of about 8 or 9 MWth. CO2 within the greenhouses is used to provide enriched levels of CO2 in air, which result in improved plant growth as well as a reduction in disease due to traces of H2S. The heating system uses plate heat exchangers (PHEs) for transferring the geothermal heat into the Plate 5: Oserian’s greenhouse heating using secondary fresh water loop. geothermal steam 12:00-13:00 STOP 4: TOUR OF OLKARIA DOMES FIELD 12:00-13:00 Tour of Olkaria Domes, drilling rigs and discharging well Surface exploration in Olkaria Domes field was completed in 1993 and drilling of the three exploration wells were carried out in 1998-1999. Drilling of 6 appraisal wells started in 2007 and the results from the drilled wells updated the conceptual model which led to the siting and drilling of the production wells. 6 GDC is currently drilling more production wells using hired Chinese Contractor. The field is earmarked to be developed as Olkaria IV. Plate 6: View of the Domes area from the north. Plate 7: Drilling well OW-903B at Olkaria Domes. Plate 8: A well discharging at Olkaria Domes 14:30-15:00 STOP 5: MAASAI CULTURAL CENTRE Visit the Maasai cultural Centre Drive through Hell’s Gate Park The Maasai is one of the acknowledged indigenous communities living adjacent to the power plant. In the Maasai village, there is a Cultural Centre, which is a major attraction for visitors interested in learning more about the Maasai culture. They also demonstrate to the visitors how they construct their traditional huts. The Morans wear their traditional regalia and display dance shows. Plate 9: Maasai dancers performing at the Maasai Cultural Centre 7 Ol’ Njorowa Gorge and Hell’s Gate Park 15:00 Drive through Hell’s Gate Park Most area of the park lies within the Ol’ Njorowa Gorge. The gorge developed from about 9,000 years ago due to erosion caused by southward outflow during the high stands of the old Lake Naivasha. The erosion cut through ashes to depths of between a few metres to more than 200 m in the south leaving volcanic necks/plugs that dot the landscape of the gorge. Hell’s Gate National park was gazetted in 1984, two years after commissioning of first unit of Olkaria I power plant. The park derives its name from the northern end of the Gorge, which due to its nature was dubbed as the ‘gate to hell’! The park has a variety of flora, fauna and avifauna. Among the animals include giraffe, zebra, buffalo, antelope etc. Birds include ostrich, eagle etc. As a measure for sustainable utilization of resources at Olkaria, KenGen signed a memorandum of understanding with Kenya Wildlife Service which is the organization charged with the responsibility of managing the park. Plate 10: View of Hell’s Gate Park from Elsa KWS Gate. In the centre is Fischer’s Tower, a volcanic plug, named after a German explorer who visited the area early last century. 17:00 Arrival Sarova Panafric Hotel END OF EXCURSION 8 .