16:00 〜 16:15
[MIS04-13] Geochemical monitoring by using a multidisciplinary approach in an active seismic region: the high Agri Valley case (southern Italy)
キーワード：Multidisciplinary approach, geochemical monitoring, thermal water, geofluids, microseismicity, high Agri valley (southern Italy)
The multidisciplinary monitoring (e.g., geochemical, geodetic and geophysical) of tectonically active areas strongly contributes to enhance the comprehension of crustal deformation processes. Fault systems and the related fractures may act as preferential conduits for natural fluids uprising at shallow levels, while the physic-chemical processes within the fault zones modify the chemical and isotopic composition of fluids. The High Agri Valley (HAV), an inter-montane basin of the Apennine chain (southern Italy) characterized by complex geological setting and active tectonics, hosts the largest onshore oil and gas reservoir in West Europe thus representing a key natural laboratory to better understand the relationship between geochemical signatures in the fluids and crustal deformations related to seismicity. The HAV is also one of the most seismic hazardous areas in Italy where a Mw 7.0 earthquake occurred in 1857 (Burrato and Valensise, 2008). Here we investigate fluids emitted at TRA_2 unproductive well, with thermal water (~28 °C), Na-HCO3 hydrofacies, and CH4-dominant bubbling gases. We estimated a total gas flux of 165 ton/year. Helium isotopes indicate a radiogenic component of fluids with a 15% of a mantle-derived helium. Given its peculiar characteristics TRA_2 well was considered suitable for long-term geochemical monitoring.
Since January 2022, it was equipped with a multiparametric probes for continuous data acquisition and remote data transmission of groundwater level, Temperature (T) and Electrical Conductivity (EC). In addition, eight discrete sampling campaigns enabled to analyze water and gas chemistry, stable isotope (O and H), C-isotope of CH4 and CO2 and noble gas. In the same area there is a dense network of geodetic and seismic monitoring stations, the latter enhanced since 2016 by the HAVO seismic network (Stabile et al., 2020), so multidisciplinary long-data series catalogues allow to reconstruct possible correlations between the local seismicity and geofluids.
Main goals of this work are: to define a geochemical conceptual model of the fluid origin (deep vs shallow) and of the processes related to their uprising to the surface; to verify eventual correlations between geochemical (long and short data series), hydro-meteorological (rainfall and air temperature) and seismic time-series. Preliminary results indicate the occurring of mantle and crustal fluids in the regional natural reservoirs. Furthermore, we also solved the processes at depth (e.g., rock-water-gas interaction) that modify the geochemical signature of fluids emerging at the surface. Combining geochemical and geological data at local and regional scale we solved that the mantle fluids are fossil and stored in the natural reservoirs for millions of years.
This study highlighted seasonal and daily water temperature fluctuations of about 0.1 and 0.03 °C, respectively. The EC values are constant, while groundwater level varies mainly with the bubbling activity. The observed values were correlated with meteorological data showing no significant correlation. During the monitoring, only isolated seismic events with Mw < 3 were recorded close to TRA_2 unproductive well; moreover, long and short geochemical data series show no correlations with seismic signals. Now, we are integrating the long geochemical data series with those from other disciplines and discuss them by using a 3D model about the origin of fluids at depth and the processes that control their chemistry during their storage in natural reservoirs and migration through the crust along the faults. Our preliminary results would be a key tool for future multidisciplinary approach for an efficient monitoring focused to the knowledge of the seismogenic processes in a complex geological area.
Burrato and Valensise, 2008
Stabile et al., 2020
Since January 2022, it was equipped with a multiparametric probes for continuous data acquisition and remote data transmission of groundwater level, Temperature (T) and Electrical Conductivity (EC). In addition, eight discrete sampling campaigns enabled to analyze water and gas chemistry, stable isotope (O and H), C-isotope of CH4 and CO2 and noble gas. In the same area there is a dense network of geodetic and seismic monitoring stations, the latter enhanced since 2016 by the HAVO seismic network (Stabile et al., 2020), so multidisciplinary long-data series catalogues allow to reconstruct possible correlations between the local seismicity and geofluids.
Main goals of this work are: to define a geochemical conceptual model of the fluid origin (deep vs shallow) and of the processes related to their uprising to the surface; to verify eventual correlations between geochemical (long and short data series), hydro-meteorological (rainfall and air temperature) and seismic time-series. Preliminary results indicate the occurring of mantle and crustal fluids in the regional natural reservoirs. Furthermore, we also solved the processes at depth (e.g., rock-water-gas interaction) that modify the geochemical signature of fluids emerging at the surface. Combining geochemical and geological data at local and regional scale we solved that the mantle fluids are fossil and stored in the natural reservoirs for millions of years.
This study highlighted seasonal and daily water temperature fluctuations of about 0.1 and 0.03 °C, respectively. The EC values are constant, while groundwater level varies mainly with the bubbling activity. The observed values were correlated with meteorological data showing no significant correlation. During the monitoring, only isolated seismic events with Mw < 3 were recorded close to TRA_2 unproductive well; moreover, long and short geochemical data series show no correlations with seismic signals. Now, we are integrating the long geochemical data series with those from other disciplines and discuss them by using a 3D model about the origin of fluids at depth and the processes that control their chemistry during their storage in natural reservoirs and migration through the crust along the faults. Our preliminary results would be a key tool for future multidisciplinary approach for an efficient monitoring focused to the knowledge of the seismogenic processes in a complex geological area.
Burrato and Valensise, 2008
Stabile et al., 2020