Sub-surface petrochemistry, stratigraphy and hydrothermal alteration of the Domes area, Olkaria geothermal field, Kenya

Shioya, Xavier M.. Sub-surface petrochemistry, stratigraphy and hydrothermal alteration of the Domes area, Olkaria geothermal field, Kenya. University of Iceland, 2015.

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  • Sub-type Master's thesis
    Author Shioya, Xavier M.
    Title Sub-surface petrochemistry, stratigraphy and hydrothermal alteration of the Domes area, Olkaria geothermal field, Kenya
    Year 2015
    University University of Iceland
    Department Faculty of Earth Sciences
    Place of Publication Reykjavik
    Publisher United Nations University Geothermal Training Programme
    Pages 100
    Language eng
    Abstract Wells OW-905A, OW-910 and OW-917 have been drilled in the Domes area of the Olkaria geothermal field. Wells OW-905A and OW-910 have been drilled inside the caldera while OW-917 has been drilled on the eastern margins of the caldera rim. The caldera rim is characterised by a ring of rhyolitic domes to the east, south and southwest margins. Plans are underway to expand production drilling to the east of the Domes field. This study presents an in-depth look at the variation in reservoir characteristics across the Domes field and to the east of the ring structure. The study also delineates magma differentiation processes involved in the evolution of the GOVC. Wells OW-905A and OW-910 cut across seven stratigraphic units namely basalt, trachybasalt, basaltic trachyandesite, trachyandesite, trachyte, rhyolite and tuff. Well OW-917 only cuts across trachyte and rhyolite. Intrusives cut by the wells include micro-granite, syenitic, trachytic and basaltic dykes. Well OW-910 has a high abundance of high-temperature alteration minerals, OW-905A has moderate abundance while OW-917 has low abundance of these minerals. Higher temperatures are observed at shallower depth in OW-910, at relatively greater depth in OW-905A and at greater depth in OW-917. High permeability is observed in wells OW-905A and OW-910. Well OW-917 shows poor permeability. Well OW-905A is located in a recharge zone, OW-910 in the up-flow zone close to the heat source and OW-917 in a down-flow zone. The main magma differentiation processes involved in generation of the basalt-trachyte suite are fractional crystallisation and magma mixing. Rhyolites have been generated through fractionation of trachytes and anatexis of syenites. The GOVC has had different episodes of eruptions. Its plumbing system consists of independent discrete magma chambers and conduits in which magma underwent modification before eruption.
    UNBIS Thesaurus STRATIGRAPHY
    GEOTHERMAL ENERGY
    PETROCHEMICALS
    Keyword Petrochemistry
    Hydrothermal alteration
    Olkaria geothermal field
    Copyright Holder United Nations University Geothermal Training Programme
    Copyright Year 2015
    Copyright type Fair use permitted
    ISBN 9789979683742
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    Created: Wed, 24 Feb 2016, 00:27:10 JST by Malfridur Omarsdottir on behalf of UNU Iceland