Adele Manzella

Investigation of geothermal structures by magnetotellurics (MT): an example from the Mt. Amiata area, Italy

During 1999 a magnetotelluric (MT) survey was carriedout on the southern margin of the Mt. Amiata geothermal region (Tuscany, Italy), with the aim of defining the shallow and deep electric structures relatedto the local geothermal reservoirs andsystem heat recharge. Local andremote d ata were collectedalong a SW–NE profile andprocessedwith two d ifferent robust algorithms. After a detailed study of the EM strike, the data were inverted and twodimensional (2D) models of electrical resistivity and impedance phase were computed. The interpretation revealeda goodcorrelation between the features of the geothermal fieldand resistivity distribution at depth. In particular, a shallow conductor (0.5–4 km) detected by the MT survey shows a goodcorrelation with the areal extension of the geothermal reservoirs. # 2003 CNR. Published by Elsevier Science Ltd. All rights reserved.

Subsurface thermal conductivity assessment in Calabria (southern Italy): a regional case study

Determining the suitability of a local area at a regional or local scale for the geothermal application of low enthalpy systems requires the knowledge of rock thermal conductivity values to evaluate the possibility of low-enthalpy heat exchange. A digital cartographic tool is also needed to synthesize the thermal properties of the underground. This tool should be easily accessible and upgradeable and thus suitable for territorial planning and environmental control. In order to address these key issues, a methodological approach was developed within the framework of the national VIGOR Project, dedicated to evaluating the geothermal potential in southern Italy. In this paper the region of Calabria was selected as a case study. Around 70 samples that were representative of the main geological formations were collected from all over the area. Thermal property tests were carried out both in dry and wet conditions, using a thermal device in accordance with the modified transient plane source method. The thermal conductivity values were then compared with data from the international literature. In order to consider the influence of the entire stratigraphic sequence on the thermal conductivity parameters, a geostatistical analysis of the available lithostratigraphic data was performed using the MATLAB toolbox Modalstrata, specially developed for this purpose. A comprehensive geothermal subsurface characterization of Calabria was thus obtained.

Contour map of the top of the regional geothermal reservoir of Sicily (Italy)

An integrated review of existing geological and geophysical data – partly acquired during oil and gas exploration – combined with new data provided by deep geothermal studies of selected key areas, was used for the 3D modeling and mapping of the top of the geothermal reservoir developed at a regional scale in Sicily (Central Mediterranean). The resulting 1:500,000 scale map covers the area of the whole Sicily (about 25,700 km2) and is devoted to represent the main input for both the thermal modeling and the evaluation of geothermal potential at a regional scale. As the map indicates the distribution at depth of a likely target for geothermal drilling, it can be also used as a rough indicator of expected drilling cost for geothermal projects. Such a map can be seen as a useful planning tool for any geothermal project, and related exploration to be carried out in the Sicily region in the future.

Surface-subsurface structural architecture and groundwater flow of the Equi Terme hydrothermal area, northern Tuscany Italy

A multidisciplinary integrated approach was used to study the structural architecture influencing the circulation pattern of geother -mal fluids in the Equi Terme area (NW Alpi Apuane, Tuscany). Geological-structural surveys were carried out to define the structural setting of the area and to characterize geometries and kinematics of fault systems. Chemical (major components) and isotopic analyses (δ18O‰, δ2H‰, 3H, δ13C‰[DIC], δ34S‰[SO4]) were performed on thermal water and cold springs. A geophysical survey was also conducted by means of both Magnetotelluric and Electrical Resistivity Tomography methodologies, in order to gain insight into the resistivity distribution at depth and to indirectly image the subsurface structure. This multidisciplinary approach proved to be a powerful tool, since it unravels the complexity of this natural geothermal system and provides useful suggestion for reconstructing the fluid circulation outflowing at the Equi Terme thermal spring. Results pointed out how the E-W oriented fault system (the Equi Terme Fault) play a key role in controlling the thermal groundwater outflow, and the chemical-physical features of this resource. This structural lineament separates high permeability carbonate complexes (footwall), in which both shallow and deep flow paths develop, from a medium-low permeability succession (hangingwall) that contains evaporitic formations from which thermal water acquires a high salinity and a composition of the Na-Cl (Ca-SO4) type. During the uprising along the fault system, the thermal water is also affected by a mixing with shallow fresh-cold waters that lead to a strong seasonal variation in the chemical-physical properties of the thermal springs.

Shallow Geothermal Exploration by Means of SkyTEM Electrical Resistivity Data: An Application in Sicily (Italy)

A novel procedure for estimating the geothermal energy exchanged by a unit volume was tested in northern Sicily (Italy), where public well data for depicting the complex geological setting were insufficient. An airborne electromagnetic survey was carried out in 2011, providing a 3D cell distribution of resistivity values. The integrated analysis of geological and resistivity data was used to identify six Litho-Electrical Units and to build a 3D geological model. This model was integrated with laboratory thermal conductivity measurements on rock samples, and was used to characterize the heat exchange at depths of up to 200 m, which in turn can be exploited for planning and designing geothermal heating and cooling plants using GSHP (Ground Source Heat Pump).

Geothopica and the interactive analysis and visualization of the updated Italian National Geothermal Database

The Italian National Geothermal Database (BDNG), is the largest collection of Italian Geothermal data and was set up in the 1980s. It has since been updated both in terms of content and management tools: information on deep wells and thermal springs (with temperature > 30 °C) are currently organized and stored in a PostgreSQL relational database management system, which guarantees high performance, data security and easy access through different client applications. The BDNG is the core of the Geothopica web site, whose webGIS tool allows different types of user to access geothermal data, to visualize multiple types of datasets, and to perform integrated analyses. The webGIS tool has been recently improved by two specially designed, programmed and implemented visualization tools to display data on well lithology and underground temperatures. This paper describes the contents of the database and its software and data update, as well as the webGIS tool including the new tools for data lithology and temperature visualization. The geoinformation organized in the database and accessible through Geothopica is of use not only for geothermal purposes, but also for any kind of georesource and CO2 storage project requiring the organization of, and access to, deep underground data. Geothopica also supports project developers, researchers, and decision makers in the assessment, management and sustainable deployment of georesources.

Building a European geothermal information network using a distributed e-Infrastructure

ABSTRACT Geothermal data are published using different IT services, formats and content representations, and can refer to both regional and global scale information. Geothermal stakeholders search for information with different aims. E-Infrastructures are collaborative platforms that address this diversity of aims and data representations. In this paper, we present a prototype for a European Geothermal Information Platform that uses INSPIRE recommendations and an e-Infrastructure (D4Science) to collect, aggregate and share data sets from different European data contributors, thus enabling stakeholders to retrieve and process a large amount of data. Our system merges segmented and national realities into one common framework. We demonstrate our approach by describing a platform that collects data from Italian, French, Hungarian, Swiss and Icelandic geothermal data providers.

ThermoGIS World Aquifer Viewer - An Interactive Geothermal Aquifer Resource Assessment Web-tool

ThermoGIS World aquifer viewer (www.thermogis.nl/worldaquifer) is a global geographical information system for assessing the at a glance geothermal energy potential from sedimentary aquifers for low enthalpy applications. It is based on a newly compiled m

Electrical Resistivity Structures and their Relation to Geological Features at the Larderello Geothermal Field (Italy)

In this paper Magnetotelluric data were used to investigate the electrical resistivity structures of the Larderello-Travale geothermal system (LTGS) in southern Tuscany, Italy. MT data acquired by ENEL (Italian power company) in the ’90 were re-analysed and two-dimensional inversions were performed along a E-W profile crossing the LTGS. The near surface inhomogeneity effects have been reduced by means of tensor decomposition and inversion for static shift. The integration of geological, geophysical and well data was performed in a three-dimensional environment (Petrel, Schlumberger) in order to improve the 2D MT inversion by setting a well-constrained a-priori model and to check inversion results supporting the interpretation. Despite the lithological features, it was clear that an important reduction of the electrical resistivity was required in the crystalline basement to fit experimental data. The results of the MT inversion along the profile have been compared with available public geophysical data.

Geothermal energy and the dissemination of information: the role of the International Geothermal Association

The International Geothermal Association (IGA), founded on 6 July 1988, is an international, worldwide, non-profit and non-governmental association whose objective and mission is to promote the research and utilization of geothermal resources, through the compilation, publication, and dissemination of scientific and technical data and information. The Information Committee (IC) of the IGA is responsible for advising the IGA Board on policies concerned with the collection, compilation, publication, exchange and dissemination of geothermal information, including information on utilization, development, technical findings, scientific research, meetings, publications and Association activities. The Committee is also responsible for the implementation of information policies determined by the Board.