| Abstract |
It is often necessary to recognize the type of the heat carrier circulating in the geothermal system. In particular, it is difficult to distinguish between hot aqueous and gaseous fluids solely basing on the resistivity and/or seismic velocity cross-sections without prior information, which may come from geology, geochemistry, well logs, etc. Even joint analysis of the resistivity and seismic velocity data does not always provide enough information for drawing sound conclusions on the heat sources or type of geothermal fluids. In particular, electromagnetic sounding is mainly aimed at detecting low resistivity anomalies, which are interpreted as hydrothermal fluids circulating in the system. In doing so, we can miss the resistivity anomalies that could reflect the gaseous/steam/supercritical fluids. Meanwhile, joint analysis of the resistivity and temperature models preferably accompanied by the gravity data may not only provide the location but also identify the type of the fluids (aqueous / gaseous or liquid / steam). In this paper we study the feasibility of mapping the supercritical geothermal reservoir and discriminating the type of fluids circulating in the geothermal system by a joint analysis of the resistivity and temperature models of the Travale area up to the depth of 10km, the latter being revealed using the indirect electromagnetic geothermometer. The comparison of the resistivity and temperature cross-sections indicates that an extensive resistive area located in the depth range of 3 - 5.5km is characterized by temperatures higher than 500¢ªC. Considering the negative Bouguer anomaly over this area, it could be interpreted as a fractured granitic massif filled by supercritical mixture of gases and vapor, which is in agreement with geochemical data. Another remarkable feature of both structures is the shallow (0-2km) inclined slab detected both in the resistivity and temperature cross-sections. It is connected with a deep reservoir and could be considered as a channel for transporting the hot steam to the surface rather than as a separate near-surface reservoir predicted here by the interpretation of seismic data. |