| Title | Precipitation Rates of Quartz Fiom Wairakei (New Zealand) Geothermal Field Brine at Temperatures of Between 200?C and 250?C and Calculation of Aquifer Surface Areas |
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| Authors | E.K. Mroczek, S. P. White & B. W. Mountain |
| Year | 2000 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | |
| Abstract | Quartz precipitation experiments appear to show that the precipitation rates h m g e o t h d fluid are much slower than predicted from models available in the literature. In particular using Dove's (1994) model the silica concentrations at the outlet of the plug flow reactor were expected to be in equilibrium with quartz between 200 "C and 250?C at flow rates up to 2 d m h (residence time 29 minutes). However only at 250?C were the outlet solutions in equilibrium with quartz. The precipitation rate of quartz calculated h m Dove's (1994) model was used to calculate Wairakei aquifer surfgce areas by matching the observed disequiliirium between measured silica concentrations and the concentrations expected if the fluids were in equilibrium with quartz. The calculated surfhce areas were between 3000 and 7000 m2/m3 of fluid if the fluid boiled one week before production reducing to between 65 and 1700 m2/m3 of fluid if the fluid boiled one month before production. These are reasonable estimates and given the very high hcture flows at Wairakei suggest boiling occurs less than 1 month before production. |