| Title | High Temperature Hydrothermal Alteration in Active Geothermal Systems a Case Study of Olkaria Domes |
|---|---|
| Authors | James Nyandigisi and Christine Katana |
| Year | 2016 |
| Conference | ARGeo |
| Keywords | Epidote, High temperature alteration, geothermal reservoir/systems |
| Abstract | The Olkaria Domes Production Field (DPF) is one of the main geothermal fields within the Greater Olkaria Geothermal Area (GOGA) that is currently being developed for geothermal energy generation. DPF is approximately bound by the Hell’s Gate-Ol’Njorowa gorge to the west and a ring of domes to the east and south of the area. Detailed surface investigations were conducted in the area in 1992/93; this developed a basic working model, from which exploration wells drilled. Three exploration wells were drilled in the field between September 1998 and May 1999. All these wells encountered High Temperature Hydrothermal Alteration Minerals (HTAMs). Since then more geothermal wells have been drilled at DPF. Several methods are used in advanced geothermal exploitation evaluation and understanding of the geothermal system and reservoir. The First occurrence of well-crystallized HTAMs is one of them. HTAMs are known to occur at stable pressure and temperature regimes for example epidote occurs at temperatures of over 250°C. To map the first appearance of HTAMs, Olkaria geothermal wells data was used to evaluate and understand the DPF geothermal reservoir. The depth of first occurrence of HTAMs in the DPF wells was compared with the present formation temperature at that same depth to identify the equilibrium, heating up and cooling down sections within reservoir system. This is important in determination of casing depths to be adopted of the DPF. This paper presents the finding of the HTAMs mapping, comparison of HTAMs occurrence with current formation temperature and recommends best casing depths within DPF within the Greater Olkaria Geothermal Area (GOGA). |