• Energy Research

We exploit the concept of the geothermal favourability, widely used for hydrothermal and EGS systems, to present an innovative methodology for assessing geopressured-geothermal resources occurring in terrigenous units in sedimentary basin plays. Geopressured-geothermal systems are an unconventional resource for power trigeneration exploiting three forms of energy from hydrocarbons, hydrothermal fluids, and well-head overpressure. This paper is intended to be a practical analytical framework for the systematic integration of the relevant data required to assess geopressured-geothermal resources. For this purpose, innovative parameters were also implemented in the methodology. The final result is the favourability map for identifying prospective areas to be further investigated for the appraisal of the geopressured-geothermal potential. We applied our methodology to the foredeep-foreland domains of the Apennines thrust belt in the Abruzzo region (central Italy). We analysed hundreds of deep hydrocarbon wells in order to create 3D geological and thermo-fluid dynamic models at a regional scale as well as to obtain information on the pressure regimes and on the chemistry of the system. The final favourability map for the Abruzzo case study is a first attempt at ranking these kinds of unconventional geothermal resources in a region that has been historically explored and exploited mostly for hydrocarbons.

Climate change and the energy crisis forced industrialized countries to contain CO2 emissions and use indigenous renewable energy sources. Geothermal energy undoubtedly has great potential, particularly thermal energy, given that 48% of the final energy consumption in the EU20 countries in 2021 was related to heating and cooling systems. The present study verifies and compares the feasibility of realizing district heating systems in two different contexts: (i) depleted hydrocarbon fields with the repurposing of existing hydrocarbon wells into geothermal wells and (ii) areas with documented geothermal resources. The two selected case studies are located, respectively, near Romentino (Northern Italy, province of Novara) and Tuscania (Central Italy, province of Viterbo). Following an assessment of the geothermal resources in the two selected case studies, specific methodological tools have been developed to evaluate the energy demand in the municipalities and determine the projects’ economics. Both case studies show positive economic indices assuming heat tariffs aligned with the values recorded in the 2020–2021 period. However, our results show how reusing hydrocarbon wells in geothermal wells constitutes an excellent opportunity to access geothermal resources, significantly reducing the necessary investment and the mining risk and strongly improving the economics of the projects.

Geothermal energy plays a key role in the green energy transition since it represents a low-carbon alternative to traditional fuels, but the high exploration costs and mining risks still hinder its use. Therefore, the reuse of pre-existing subsurface geological data can represent a way to counteract these limiting factors and promote the use of geothermal resources. We reconstructed a 3D geological model of the Guardia Lombardi area (Campania Region, southern Italy) and evaluated its geothermal potential interpreting vintage oil and gas subsurface data (i.e., seismic reflection profiles and well data). The exploitation potential of the geothermal resource and the related costs were also evaluated. The study revealed the presence of a geothermal reservoir with 125 °C at just 2300 m depth and an exploitation potential of about 70 kg/s, employable for residential heating and/or cooling and for electricity production in the nearby Grottaminarda town, with an appreciable economic benefit. These results demonstrate how the reuse of pre-existing subsurface geological data provided by past oil & gas exploration can considerably reduce costs and mining risks associated with geothermal resource exploration, contributing to a faster and considerable reduction in CO2 emissions.

In the frame of the Integrated Method for Advanced Geothermal Exploration (IMAGE) Project, a reliable exploration and resource assessment workflow was implemented on the basis of an integrated and multidisciplinary approach. Our study addressed to a better understanding of the thermal structure of the deepest part of the Larderello geothermal field (Southern Tuscany, Italy) by integrating structural, geological, geochemical, geochronological, petrological and geophysical data. With the aim to characterize the reservoir located nearby an important seismic reflector (the K-horizon), we systematized the available data and, successively, we applied a numerical thermal modelling approach to test our hypotheses and concepts.

Geothermal energy has similar social acceptability issues as other renewable energy technologies. The territory of a geothermal project should be known in depth, understood and respected, including the public and its value, the energy issues and the entire socio-economic and political context as well. This knowledge can only be acquired with the tools provided by social sciences. It will be the key to build a project adapted to the territory, to communicate with and engage the public in a suitable way. Three tools helpful in fostering constructive interactions with the public have been examined: information sharing, creating local benefits, and public participation.

Geothermal plants have been producing power in Italy for more than a century. Since local opposition to geothermal development is often fuelled by incomplete and inaccurate environmental information, this paper provides a comprehensive description of the effect of geothermal development on the air, water and soil and investigates potential disturbance from noise, subsidence, and seismicity, as well as the visual impact on the local area. After discussing the risks associated with the geothermal development and the reference data, the paper describes the wide-reaching environmental monitoring and mitigation measures in Italy that have maintained impact values below the thresholds defined by European and Italian regulation. The social benefits for areas where geothermal energy is developed are also described, with the aid of case studies highlighting that citizens do not feel that they are sufficiently informed to have a voice in the innovation process. A regular and comprehensive review of the geothermal environmental and safety regime, as the one carried out in this paper, and a mutual exchange of knowledge between the different stakeholders should be strongly encouraged.

Within the framework of the VIGOR project, the geothermal assessment of medium enthalpy resources in the "Guardia dei Lombardi" area, located in the Campania region (Southern Italy, Province of Avellino), has been undertaken. Due to the intense hydrocarbon exploration, carried out particularly during the 1956-1996 period, a wide dataset exists in the study area. This dataset, made up by seismic reflection profiles, well data, logs and cores, has been accesible to our research group thanks to the cooperation agreement with the Italian ENI oil company. The overall structural-stratigraphic setting of the reservoir/caprock system has been defined on the basis of the integrated interpretation of the available composite dataset of surface and subsurface geological, geophysical and geochemical information. The main geothermal reservoir is made up by a fractured carbonate reservoir, that is constituted by the Cretaceous-Eocene sequence of the Apulian shallow water carbonate platform (e.g., Scrocca, 2010 and reference therein). Following the Apennine orogenesis, the Apulian platform was deformed to shape a buried antiformal stack (Nicolai & Gambini, 2007). In the study area (Fig. 1) the culmination of the uppermost thrust unit reaches a depth of about -250 m below the sea level (i.e. about -1125 m below the ground level). According to well test results, the reservoir fluids are mainly composed of CO2, which rests above an accumulation of brackish water in the central and upper part of the culmination of the deep carbonatic aquifer (i.e., Monte Forcuso 1 and 2 wells). The reservoir fluid do not show a free gas phase but only saline water along the flank of the buried anticline (e.g., Bonito 1 Dir, Ciccone 1 wells). As already suggested by previous assessments (e.g., ENEL, 1987; ENEL/ENI/CNR/ENEA, 1994), available well data temperature highlight the presence of reservoir fluid that reaches temperature of 120°C at depth of 3000 m below ground level (e.g., Bonito 1 Dir well). This conclusion is also in agreement with estimations of reservoir fluid temperature up to about 124°C calculated using different geothermometers by Duchi et alii (1995) on water samples collected from thermal springs (e.g., Terme di San Teodoro). On the basis of well tests, cores analysis and mud losses/absorptions, it has been possible to re-estimate the reservoir properties, confirming quite good permeabilities for the fractured carbonate reservoir. One of the main results of this research is the development of an integrated 3D geological model which provides the base for a detailed assessment of the possible geothermal exploitation of the carbonate reservoir. The preliminary results of our analysis suggest that the "Guardia dei Lombardi" site could be indicated as an interesting area for the geothermal medium enthalpy exploitation, although the presence of the CO2 gas cap should be carefully evaluated.