Traccianti e indicatori geochimici per la valutazione di risorse geotermiche

Responsabili di progetto

Orlando Vaselli, Sheng Rong Song

Accordo

TAIWAN - NSTC - National Science and Technology Council

Bando

CNR-MoST (ex NSC) 2016-2017

Dipartimento

Scienze del sistema terra e tecnologie per l'ambiente

Area tematica

Scienze del sistema Terra e tecnologie per l'ambiente

Stato del progetto

Rinnovo

Relazione per il rinnovo

report-previous-project.pdf

Proposta di ricerca

Geothermal energy is a renewable energy, which is generated and stored in Earth. The exploitation of geothermal energy contains several stages; fluid geochemistry is particularly important on investigating geothermal reservoirs. In this project, we are using several geotracers (e.g. noble gases) and geoindicators (e.g. H2, CH4) to calculate the deep temperature and estimate the geothermal energy along with those associated with the liquid phase, such as Cl, B, Li, Rb, Cs and Na, K, Mg, Ca, SiO2, respectively. In the previous project, the Taiwan and Italy team has investigated the Tatun volcanic complex with promising results in terms of geothermal exploration since equilibrium temperature >400 °C where calculated by using inorganic (H2-CO-CO2-H2O system at redox conditions controlled by the SO2-H2S buffer) and organic (propane-propene system) gas compounds. The relatively high abundance of CH4 and the respective isotopic ratios have indicated the contribution of a thermogenic, shallow source, which affects the deep component. This observation was validated when the cold CH4-rich gas discharges from the southern part of Tatun were collected and analyzed since they show for the organic gas component, similarities with the Tatun fumarolic gases.
For the next two years project, owing to the good achievements gathered from the Tatun volcanic area, we are planning to carry our a detailed investigation on the Ilan region, which is located in the northern-eastern sector of the Island of Taiwan. Ilan county is considered, along with Tatun, one of the most important geothermal areas of the country. Here, many gas-rich hot and cold springs are discharging in the whole territory of Ilan. This area can be considered a pioneer case in the development of geothermal energy. In fact, several investigations have taken into account this area and particularly in the Ilan Plain. Nevertheless, a detailed investigation of the geochemical and isotopic features of the fluid discharges is still lacking. As a consequence, in this two years project we are willing to carry out a systematic collection of the most significant fluid (thermal waters and gases) discharges and apply a similar geochemical and isotopic approach used for the Tatun volcanic area. Another interesting aspect that characterizes the Ilan Plain is the presence of relatively deep wells, which are expected to provide more exhaustive information along with the surface fluid discharges. Water and gas samples will also be collected in the surrounding areas of the Ilan Plain with the aim to define the possible extent of the geothermal anomaly. Furthermore, geostructural investigations are expected to be carried out to relate the fluid discharges with the tectonic setting of the area. Such studies are very important in terms of geothermal exploration since they produce useful information to understand the geological deep setting of the area and, possibly, comprehend the productive fault systems.
Contemporarily, the Taiwan colleagues when visiting Italy will be involved in a sampling campaign at the Island of Vulcano (Sicily) where low (100 °C) to relatively high (400 °C) temperature fumarolic gases are discharged from the flanks and the crater summit, respectively, and the not exploited geothermal field of the Vicano-Cimini volcanic district (central Italy). As for the Ilan Plain gases, the Taiwan colleagues will be in charge of the isotopic ratios of the noble gases, which are useful tracers of the deep sources feeding the surface gases.
The Taiwan and Italian working team consists of researchers with a large experience in the field of fluid geochemistry and structural geology. Their different scientific competencies are expected to adequately respond to the aims of the project.
The results deriving from this study will disseminate through international congresses such as the WRI (Water-Rock Interaction, October 2016, Évora, Portugal) and the IMOG (International Meeting of Organic Geochemistry, September 2017, Florence, Italy) meetings (for the participation to these congresses CNR-IGG or Department of Earth Sciences funds will be used) and a workshop that will be held in Florence or Taipei at the end of the project to summarize the principal achievements.

Obiettivi della ricerca

Geochemical tracers, i.e. ions, molecules or isotopes not affected by secondary chemical reactions once entering a geological system such a geothermal reservoir, and geoindicators, i.e. ions, molecules or isotopes expected to participate at secondary chemical reactions at controlled physical-chemical conditions, are useful parameters, which can successfully be applied to thermal water and gas discharges during geothermal exploration for estimating i) the geochemical features of geothermal reservoirs and ii) their equilibrium temperature and redox conditions. The working team can operate within a wide spectrum of geochemical and isotopic parameters, allowing to constrain the physical-chemical features of any geothermal system and integrated these data with those obtained by geostructural investigations. Thus, the main aim of the present proposal is that to depict a geological-geochemical conceptual model the Ilan area (northern-eastern Taiwan), where this approach has not been applied, although geophysical studies and preliminary geochemical data have indicated this area as a potentially favorable site for geothermal exploitation. The previously described concepts will be applied to two Italian hydrothermal systems: a) the active volcanic system of Vulcano (characterized by relatively high temperature fumarolic discharges) and b) the extinct volcanic complex of Vicano-Cimini since previous investigations have suggested this area is a not exploited geothermal field.

Ultimo aggiornamento: 08/06/2025