| Title | Characterisation of tonalite and andesite prior to reaction with CO2-rich fluids |
|---|---|
| Authors | B. Lynne, A. Morriss, E. Kaya, L. Adam, J. Mering |
| Year | 2024 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Andesite, tonalite, core, reversing carbon emissions, CO2-rich injectate |
| Abstract | The physical properties of two cores from high-temperature geothermal fields were examined and characterised as part of CO2-rich fluid injection investigations. One core is tonalite from injection well NM9 (3201.1-3201.55 m depth) in the Ngā Tamariki geothermal field, New Zealand. The second core is andesite from 972.3-972.6 m depth, from well N3 in the Palinpinon geothermal field, the Philippines. To characterise the rock properties of the cores, analytical methods used included: (1) Scanning Electron Microscopy to assess microscopic void dimensions, distribution, connectivity and to examine reactive surfaces, (2) X-Ray Diffraction and petrography to determine the mineralogy, (3) X-Ray Fluorescence to identify elemental compositions, (4) Computerised Tomography and density and porosity measurements to establish rock density, and connected flow pathways, (5) Porosity and seismic velocity testing, to assess rock porosity, and (6) Compressibility testing to document rock strength. The tonalite and andesite core samples were then placed inside an experimental chamber and saturated with CO2-rich fluid. The experimental chamber conditions were 140°C and 10 barg within a chamber containing pure water saturated with CO2. The resulting fluid had a measured pH of 5.5. Samples were exposed to these conditions for 24 hours. The same analytical methods used to characterise the tonalite and andesite samples at the pre-experiment stage, will be repeated after they have been saturated with CO2-rich fluid inside the experimental chamber. To date, compressibility testing has been performed on both the tonalite and andesite cores postexperimental chamber analyses. Compressibility results revealed a weakening of both the tonalite and andesite cores after exposure to CO2-rich fluid. |