| Title | THE POTENTIAL OF GEOTHERMAL EMISSIONS STORAGE IN THE TAUPŌ VOLCANIC ZONE, NEW ZEALAND |
|---|---|
| Authors | I. Galeczka, I. Chambefort |
| Year | 2021 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | CCS, CO2 mineral storage potential,Wairakei, Kawerau, Rotokawa, CarbFix |
| Abstract | New Zealand’s low carbon aspirations are in line with the goals of the Paris Agreement to constrain anthropogenic warming to 1.5–2°C. The enhanced utilisation of renewable geothermal resources is crucial to reduce the greenhouse gases emissions sourced from the energy sector that is the third largest industrial emitter in the country after national transport and manufacturing industries. Although more than a magnitude lower in CO2 release comparing to coal-burning power plants, New Zealand geothermal power stations emit on average 76 gCO2eq/kWh, which equals to about 530 ktCO2/yr. As a result, necessary efforts must be undertaken to transform the geothermal industry into a neutral or negative carbon emissions energy source. Two solutions are currently developed worldwide to mitigate anthropogenic geothermal CO2. The first one is the reinjection of the emissions back to the reservoir with the reinjection waters. The second one that is yet to be tested in New Zealand is the CarbFix mineral storage method. The latest is currently developed in Iceland where about 12 kt of CO2 and 8 kt of H2S are captured and injected annually into the subsurface. The CO2 and H2S are mineralised into carbonate and sulphide minerals as a result of interaction between the reinjected gases and the basaltic host rock that is enriched in divalent cations (Ca, Mg, Fe). This study aims to investigate three geothermal areas for their CO2 and H2S storage potential: Wairakei, Kawerau, and Rotokawa geothermal fields, all located in the Taupō Volcanic Zone, New Zealand. In contrast to the basaltic reservoir at the CarbFix injection site, here, the subsurface consists of silicic tuff, andesitic greywacke, andesite, and rhyolite that are depleted in divalent cations, possibly limiting the CO2 mineral storage. To address these limitations, geochemical reaction path models were created using the compositions of the geothermal reservoir fluids and rocks. The outcome of the simulations was used to assess the maximum mineral storage capacity of these geothermal sites. |