| Title | Tauranga Geothermal System: Temperature Distribution |
|---|---|
| Authors | L. Janku-Capova, S.J. Zarrouk, M.P.S. Zuquim |
| Year | 2022 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Tauranga geothermal system, temperature logs, geothermal gradient |
| Abstract | The city of Tauranga in the Bay of Plenty region of New Zealand lies on a warm (30 – 70°C) water geothermal resource classified as Geothermal Management Group 5 by the Bay of Plenty Regional Resources Plan. Despite the widespread use of the resource, mostly for bathing and frost protection and irrigation, this reservoir`s temperature distribution and extent is poorly understood. We constructed subsurface temperature maps in 50 m depth intervals to 300 m below sea level using temperature profiles from 40 wells in the Tauranga and Maketu low-temperature geothermal fields to constrain the resource and localise the hottest zone. These maps “slices” show two temperature anomalies. One, hotter (∼50°C) but poorly constrained due to insufficient data, lies southwest of Maketu Peninsula between Maketu and Te Puke. The other is below the city of Tauranga. Both thermal anomalies are confirmed by other evidence. The Maketu anomaly has been subject to interest since the 1960s due to the presence of nearby hot springs and a low resistivity anomaly. The Tauranga anomaly is expected as hundreds of water wells are used mostly for domestic and recreational purposes, with discharge temperatures mostly in the range of 35–45°C. Additional measurements, especially temperature logs in more wells in the area, as well as thermal conductivity and permeability measurements on samples of representative lithologies (rhyolites, andesites, ignimbrites and sediments of the Tauranga Group), are needed for a deeper understanding of this low-temperature geothermal resource and its potential commercial use. The Maketu anomaly is supported by geological, geophysical and hydrogeological evidence, so it might be worthy of further exploration. |