| Title | Decadal gas monitoring for geothermal production and exploration: Andean experience |
|---|---|
| Authors | P. Robidoux, M. Inostroza, J. Walter |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | Combining compositional gas sampling data from the Central-South Volcanic Zone of the Andes (Chile) provides a comprehensive overview for exploring and developing high-enthalpy geothermal systems. Decadal geochemical sampling along the South American volcanic arc offers critical insights for geothermal exploration, with at least nine sites used for resource power estimations (32–128 MWe). Characterizing CO₂-rich gas phases in hydrothermal systems enhances understanding of gas composition and associated physicochemical processes in wells drilled into high-enthalpy geothermal systems. A quantitative principal component analysis (PCA) of the dataset shows that gas chemistry in geothermal plants and exploration fields fluctuates between reducing and weakly oxidizing conditions, whereas natural fumarole systems exhibit extreme variations. Oxidation state (H₂/H₂O ratio) and vapor fraction increase upon cooling from the hydrothermal reservoir. Ar content and lower N₂/Ar ratios in recent samples highlight contrasts between natural hydrothermal, industrial as geothermal environments. Geological and gas parameters indicate optimal conditions for locating high-enthalpy systems occur when N₂/Ar correlates with reservoir temperature and H₂S/SO₂ ratios exclude volcanic halogen or SO₂ inputs. Reduced conditions are further indicated by the H₂/H₂O ratio. These conditions are optimum according to literature when an impermeable geological barrier supports a short distance between fumarole sampling sites and the nearest volcanic crater, minimizing fluid contamination from air. This integrated approach demonstrates how gas compositional analysis can guide the identification of high-enthalpy geothermal resources, improving both exploration accuracy and resource evaluation. |