| Title | Reaction Path Modelling in Basalt–CO₂–H₂O Flow-Through Experiments |
|---|---|
| Authors | Koji Mori, Atsushi Neyama, Kentaro Masuoka, Hajime Yamamoto, Naoki Nishiyama, Masao Sorai, Amane Terai |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | The behavior of supercritical CO₂ in geothermal reservoirs, particularly its geochemical interactions with host rocks under high-temperature and high-pressure conditions, is not yet fully understood. In particular, the effects of secondary mineral precipitation and re-dissolution on reservoir porosity and permeability remain unclear. We conducted reactive transport modelling using the TOUGHREACT code to reproduce flow-through column experiments involving basalt–CO₂–H₂O systems and identified the dominant geochemical reaction pathways. The results suggest that two or more distinct transport mechanisms may coexist within the system. Post-experimental analysis revealed that, across all three experimental cases with different pressure differentials, dissolution was localized near the inlet zone of the column. In contrast, the downstream part of the column showed concurrent dissolution of the basalt matrix and formation of secondary phases such as boehmite and beidellite. A measurable decrease in sample weight was also confirmed after the experiments. We successfully identified a common reaction pathway model (THC-coupled) capable of reproducing these key experimental features, including solute concentration, mineralogical changes, and mass loss trends. This model was further extended to a field-scale demonstration using a typical five-spot well configuration, with simulations highlighting the short-term behavior following CO₂ injection. |