Fluid-rock interaction experiments with andesite at 100°C for potential carbon storage in geothermal reservoirs

Geothermal energy extraction often results in the release of naturally occurring carbon dioxide (CO₂) as a byproduct. Research on carbon storage using volcanic rock types other than basalt under both acidic and elevated temperature conditions has been limited so far. Our study uses batch reactor experiments at 100°C to investigate the dissolution of andesite rock samples obtained from an active geothermal reservoir in Sumatra (Indonesia). The samples are subjected to reactions with neutral-pH fluids and acidic fluids, mimicking the geochemical responses upon reinjection of geothermal fluids, either without or with dissolved acidic gases, respectively. Chemical elemental analysis reveals the release of Ca²⁺ ions into the fluids through the dissolution of feldspar. The overall dissolution rate of the rock samples is 2.4 × 10^–11 to 4.2 × 10^–11 mol/(m² · s), based on the Si release during the initial 7 h of the experiment. The dissolution rates are about two orders of magnitude lower than those reported for basaltic rocks under similar reaction conditions. This study offers valuable insights into the potential utilization of andesite reservoirs for effective CO₂ storage via mineralization.