CO2 Degassing in Sicily (Central Mediterranean) as Inferred from Groundwater Composition

The circulation of groundwater is influenced by several factors, including permeability changes due to the dynamics of the stress field acting along tectonic discontinuities. Open faults can act as preferential pathways for the escape of crustal and subcrustal gases, such as CO2, towards the surface, allowing their chemical interaction with meteoric fluids. Here, we present the first map of dissolved CO2 partial pressure in the groundwater of Sicily, Italy. Based on the chemical analysis of 557 samples of groundwater, which were collected in wells and springs, we calculated the related CO2 partial pressure (PCO2) using PHREEQC software. The spatial distribution of the calculated PCO2 values highlights a general homogeneity at the regional scale, interrupted by positive anomalies linked to the main seismogenic or volcanic areas. Faults work as preferential escape pathways for deep CO2. The subsequent CO2–water–rock interaction determines the chemical composition of circulating water. As a consequence, groundwater composition can be successfully used to identify anomalous degassing areas.

Anomalies in groundwater composition caused by earthquakes: examples and modeling issues

The examples of modeling hydrogeochemical anomalies recorded in the observation wells and sources of Kamchatka caused by the preparation of strong local earthquakes and the impact of seismic waves are considered. As a working hypothesis explaining the formation of such anomalies, assumptions about the change of conditions (1) of mixing of two waters, contrasting in chemical composition and (2) interaction in the «water – rock» system are used.

HYDROGEOLOGICAL STRATIFICATION OF CUTS OF THE ANABARO-KHATANG OIL AND GAS FIELD

A scheme of detailed hydrogeological stratification of Anabaro-Khatanga oil and gas region was constructed on the basis of complex interpretation of well logging data, results of core description and hydrogeochemical analysis of ground waters and the data of stratigraphy, lithology, sedimentology, geology and hydrogeology. The waterbearing stages, complexes, aquafers and seals were allocated. Groundwater composition are characterized. Different types of hydrogeological section are given.