Stanford Geothermal WorkshopFebruary 9-11, 2026

The Olkaria geothermal field, located within the Great Rift Valley in Kenya, is characterized by diverse geothermal manifestations, including geothermal grass, silica sinters, altered ground, and prominently steaming grounds and fumaroles. These fumaroles exhibit high temperatures ranging from 70°C to 90°C, indicating a substantial subsurface potential for geothermal energy harnessing and utilization. Most drilled wells in the area show high temperatures at reservoir depths greater than 200 ℃. Integrated geophysical methods have been employed to identify subsurface geological structures that govern the geothermal reservoir. These methods correlate resistive and dense signatures, providing extensive information about subsurface geological formations. The geothermal gradient in the Olkaria field is estimated at about 45°C per kilometer. The formations exhibit a resistive propylitic reservoir zone with high-density bodies, characterized by resistivity values greater than 70 Ωm and densities greater than 2600 kg⁄m^3 . Although most production wells in the Olkaria geothermal field are drilled to depths of about 3 km, 3-D resistivity inversion models suggest the presence of a heat source at depths of approximately 5 – 8 km below the surface and a reservoir depth of about 2.5 – 4 km. This indicates potential for future expansion by deepening production wells beyond 3000 m. A structurally conspicuous anomaly trending NNE-SSW has been observed, connected to some high-producing wells in the Olkaria Domes field. Microgravity observations reveal mass changes across the field, with primary natural recharge appearing to come from the northwest and east of the Domes field. The potential recharge zone is marked by a high resistive signature, which may indicate cold water infiltration into the reservoir system.

Topic: Geophysics