Characterizing Permeability from Geological and Geochemical Data in the Olkaria Domes Field in Kenya.

  • Harriet Nkatha Achini Pan African University Life and Earth Sciences Institute
  • Olubunmi C Adeigbe University of Ibadan
  • Bernard Kipsang Rop, PhD Jomo Kenyatta University of Agriculture and Technology
Keywords: Geothermal, Dome, Permeability, Mineral phase, Geothermal gradient, Weak zone
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Abstract

Olkaria geothermal field is located in the Kenyan Rift Valley that is a part of the Great East Africa Rift System (EARS). The geothermal field continues to be associated with a high geothermal gradient that arises from shallow magmatic activities which are ongoing in the enormous igneous province. Exploration and drilling of wells that were undertaken in the past revealed the existence of exploitable geothermal steam. The Olkaria field is divided into seven sections namely; Olkaria East field, Olkaria North East field, Olkaria North West field, Olkaria South East field, Olkaria South West field, Olkaria Central field, and Olkaria Domes field. The productivity of the geothermal wells continues to be influenced by factors such as subsurface permeability. Permeability is one of the parameters used for the characterization of geothermal fields. Other parameters used for characterization are associated with geotechnical weak zones and include features such as; fractures, vein bodies, and deformational fault systems. The research work involved geoscientific characteristics of the Olkaria Domes field based on the geological and geochemical factors to characterize the permeability of the field. The research involved studying rock types in the area by analysing drill cuttings obtained from six drilled wells in the Olkaria Domes field. Three of the six drill wells were considered for correlative description for the purpose of this paper. Correlation of the main lithologies and zones for loss of circulation in the field was also undertaken as well as the creation of mineralogical maps to capture the distribution of the minerals that were derived from hydrothermal weathering processes. The depths and formation for major loss circulation zones in the reservoir section of the field were identified and included in the description. Analysis of soil gas survey using radon as a geochemical tool in the Domes field was also carried out successfully. The relatively high levels of the soil gas ratios that were analysed captured the ratio distribution of carbon dioxide to radon at various reservoir depths. The detection of the two gases at the surface showed the existence of permeable zones which facilitated the movement of the gases through the fault-controlled structural systems of the studied Olkaria Domes field.

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References

Baker, B. T., & Wohlenberg, J. (1971). Structure and evolution of the Kenya Rift Valley. Nature, 229(5286), 538-542.

Baker, B. H., Mitchell, J. G., & Williams, L. A. J. (1988). Stratigraphy, geochronology and volcano-tectonic evolution of the Kedong–Naivasha–Kinangop region, Gregory Rift Valley, Kenya. Journal of the Geological Society, 145(1), 107-116.

Clarke, M.C.G., Woodhall, D.G., Allen, D., and Darling, G., 1990: Geological, volcanological

and hydrogeological controls of the occurrence of geothermal activity in the area surrounding Lake Naivasha, Kenya. Ministry of Energy report.

Haerudin, N., Wahyudi., Munadi, S., & Suryanto, W. 2013. A Soil Gas Radon Survey to

Determine Fault at Southern Part of Rajabasa Geothermal Field, Lampung Indonesia. International Journal of Engineering & Technology, IJET-IJENS Vol. 13 (1), pp. 75-81

Heap, M. J., Reuschlé, T., Farquharson, J. I., & Baud, P. (2018). Permeability of volcanic rocks to gas and water. Journal of Volcanology and Geothermal Research, 354, 29-38.

Lagat, J. K. E., Arnorsson, S., & Franzson, H. (2004). Geology, hydrothermal alteration and fluid inclusion studies of Olkaria Domes geothermal field, Kenya. Háskóli Íslands, jarð-og landfræðiskor.

Mwania, M. M. (2015). Evaluation of subsurface structures using hydrothermal alteration mineralogy-A case study of Olkaria South East field. GRC Trans, 39, 559-566.

Omenda, P. A. (1997). The geochemical evolution of Quaternary volcanism in the south-central portion of the Kenya Rift. The University of Texas at El Paso.

Omenda, P. A. (1998). The geology and structural controls of the Olkaria geothermal system, Kenya. Geothermics, 27(1), 55-74.

Omwenga, B. M. (2019). Characterization of Subsurface Permeability of the Olkaria East Geothermal Field. 44th Workshop on Geothermal Reservoir Engineering. Stanford University, Stanford, California, Feb 2019. SGP-TR-214.

Rop, B. K. and Namwiba W. H. (2018). Fundamentals of Applied Geology: Competency and Evaluation Approach. Verlag/Publisher: LAP LAMBERT Academic Publishing.

Rop, B. K., Anyona, S., Kipseba, E. K., Namwiba, W. H. and Kipkiror, L. J. (2020). Review of Geothermal Resources as Manifestations of Volcanism in Eastern Africa. Proceedings of the Sustainable Research and Innovation Conference, JKUAT Main Campus, Kenya.

Schön, J. H. (2015). Physical properties of rocks: Fundamentals and principles of petrophysics. Elsevier.

Simiyu, S. M. (2010, April). Status of geothermal exploration in Kenya and future plans for its development. In Proceedings world geothermal congress (pp. 25-29).

Smith, M. C. (1983). A history of hot dry rock geothermal energy systems. Journal of Volcanology and Geothermal Research, 15(1-3), 1-20.

Smith, M., and Mosley, P., 1993: Crustal heterogeneity and basement influence on the development of the Kenya rift, East Africa. Tectonics, 12, 591-606.

Whitebread, D. H. (1976). Alteration And Geochemistry of Tertiary Volcanic Rocks In Parts Of The Virginia City Quadrangle, Nevada.

Published
5 October, 2021
How to Cite
Achini, H., Adeigbe, O., & Rop, B. (2021). Characterizing Permeability from Geological and Geochemical Data in the Olkaria Domes Field in Kenya. East African Journal of Environment and Natural Resources, 3(1), 161-182. https://doi.org/10.37284/eajenr.3.1.429