The composition of high temperature geothermal fluids in New Zealand producing geothermal fields

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Mroczek, E.K.; Climo, M.; Evans, D. 2017 The composition of high temperature geothermal fluids in New Zealand producing geothermal fields. Revised ed. Lower Hutt, N.Z.: GNS Science. GNS Science report 2014/68 21 p.

Abstract: This literature review updates and summarises the chemical composition of geothermal waters from wells in the Taupo Volcanic Zone and Ngawha, with the aim of characterising the “typical” reservoir water composition for the developed, high-temperature geothermal systems. The reservoir liquid composition is also calculated to atmospheric pressure which is the maximum amount of steam separation. Most information was available on the major chemical components: Na, K, Ca, Cl, B, SiO2, SO4 and HCO3, but also minor components of Li, Rb, Cs and Mg. This study also presents limited information on trace elements and precious metals, in particular Au, Ag and Cu but data for these species is limited in the surface discharges. The representative concentration of each species is provided for nine high temperature geothermal fields; namely Ohaaki, Kawerau, Mokai, Ngatamariki, Ngawha, Rotokawa, Rotorua, Tauhara, Wairakei and Ngawha. The estimated annual flux of each species is given based on the representative concentration multiplied by the consented fluid take for the producing geothermal fields. This compositional and flux data provides input data for determining the economics of mineral extraction from New Zealand’s geothermal fields. This Report is an amended copy of GNS Science Report 2014/68 issued in 2015. Table 4.2 “Total annual flux of the major elements for producing geothermal fields in New Zealand” has been corrected so that all values (except) bicarbonate are calculated using the total discharge concentrations given in Table 4.1. (auth)