Geothermal deep closed-loop heat exchangers: A novel technical potential evaluation to answer the power and heat demands, 2022
This paper investigates and optimises the thermal performance of deep closed-loop heat exchanger ... more This paper investigates and optimises the thermal performance of deep closed-loop heat exchanger (DCHE) systems by applying a computational numerical approach. The investigated DCHE configuration accounts for two deep vertical boreholes, an injection and a production well, connected by a horizontal borehole at depth and an insulated pipeline at the surface, establishing an effective closed-loop system. First, a parametric sensitivity study explores the effects of the environmental, design and operating variables on the production temperature. The simulation uses realistic geological and geothermal conditions, depths, circulation rates and injection temperatures. Two complex numerical models are then solved for site-specific DCHEs in different geological scenarios: a foreland basin and a convergent margin hosting low-to-intermediate and high-temperature geothermal resources, respectively. Production temperatures beyond 40-60°C and 100°C, sustainable for both heat and electric power generation, are obtained, depending on the geothermal conditions and closed-loop dimensions. Furthermore, circulation rates of 0.02-0.04 m 3 s − 1 are cost-effective, and the system's efficiency and sustainability increase when a fluctuating and periodic heat extraction strategy is employed. When efficiently operated, DCHEs are a viable solution for renewable energy production and should be integrated into the local heat market and distribution network infrastructure.
This paper describes a data integration tool used to identify potentially undiscovered geothermal... more This paper describes a data integration tool used to identify potentially undiscovered geothermal resources in the island of Sicily. The factors facilitating the recovery of exploitable geothermal energy were defined, and their spatial correlation established by Geographic Information System (GIS) models. By prioritizing favourable conditions using an Index Overly method, "favourability" maps of Sicily were obtained. The maps considered both geological and economic aspects, and energy recovery was considered for current technologies. Our approach and maps are useful for developing and planning local or national energy policies including geothermal energy.
The growing interest on renewable energy sources is stimulating new efforts aimed at the assessme... more The growing interest on renewable energy sources is stimulating new efforts aimed at the assessment of geothermal potential in several countries, and new developments are expected in the near future. In this framework, a basic step forward is to focus geothermal investigations on geological environments which so far have been relatively neglected. Some intracontinental sedimentary basins could reveal important low enthalpy resources. The evaluation of the geothermal potential in such geological contexts involves the synergic use of geophysical and hydrogeological methodologies.
<p>Based on a joint analysis of geothermal indicators (e.g. temperature map... more <p>Based on a joint analysis of geothermal indicators (e.g. temperature map at different depth, surface heat flux) and practical features (e.g. restricted areas, existing research lease), two promising areas in southern Tuscany were identified to perform a more detailed geothermal resource characterization. An area is located on the north-east of the Larderello-Travale geothermal field, and the other one is located on the west of the Mt. Amiata geothermal field.</p> <p>A quantitative geothermal resources assessment was performed in the aforementioned areas of Tuscany by solving numerical thermo-fluid dynamic models and by computing the geothermal potential using the ‘ThermoGIS’ software, as further developed for the Italian case (Trumpy et al., 2016).</p> <p>First of all, geological and geophysical data required for geological and thermo-fluid dynamic modelling were collected and organised. The geological data were used to build a 3D geological model of the two areas of interest suitable for numerical simulations. Static temperature data gathered from the Italian National Geothermal Database together with site-specific heat flow measurements were used to calibrate the simulated steady state temperature distribution.</p> <p>The geothermal potential computed by integrating geological, thermal and petro-physical information implementing the volume method used in ThermoGIS provided estimates of the heat in place and the geothermal technical potential maps. The resulting technical potential in the area close to Larderello –Travale is 330 MW<sub>e</sub> and in the Mt. Amiata sector is 50MW<sub>e</sub>.</p> <p>References</p> <p>Trumpy E., Botteghi S., Caiozzi F., Donato A., Gola G., Montanari D., Pluymaekers M., Santilano A., Van Wees, J.D., Manzella A. Geothermal potential assessment for a low carbon strategy: a new systematic approach applied in southern Italy. Energy 103, 167-181, 2016.</p>
International Journal of Terrestrial Heat Flow and Applications
We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m de... more We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m depth range to unravel thermal regime beneath the central-northern Apennines chain and the surrounding sedimentary basins. We particularly selected deepest bottom hole temperatures, all recorded within the permeable carbonate Paleogene-Mesozoic formations, which represent the most widespread tectono-stratigraphic unit of the study area. The available temperatures were corrected for the drilling disturbanceand the thermal conductivity was estimated from detailed litho-stratigraphic information and by taking into account the pressure and temperature effect. The thermal resistance approach, including also the radiogenic heat production, was used to infer the terrestrial heat flow and to highlight possible advective perturbation due to groundwater circulation. Only two boreholes close to recharge areas argue for deep groundwater flow in the permeable carbonate unit, whereas most of the obtaine...
This paper describes a data integration tool used to identify potentially undiscovered geothermal... more This paper describes a data integration tool used to identify potentially undiscovered geothermal resources in the island of Sicily. The factors facilitating the recovery of exploitable geothermal energy were defined, and their spatial correlation established by Geographic Information System (GIS) models.
We exploit the concept of the geothermal favourability, widely used for hydrothermal and EGS syst... more 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.
We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m de... more We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m depth range to unravel thermal regime beneath the central-northern Apennines chain and the surrounding sedimentary basins. We particularly selected deepest bottom hole temperatures, all recorded within the permeable carbonate Paleogene-Mesozoic formations, which represent the most widespread tectono-stratigraphic unit of the study area. The available temperatures were corrected for the drilling disturbance and the thermal conductivity was estimated from detailed litho-stratigraphic information and by taking into account the pressure and temperature effect. The thermal resistance approach, including also the radiogenic heat production, was used to infer the terrestrial heat flow and to highlight possible advective perturbation due to groundwater circulation. Only two boreholes close to recharge areas argue for deep groundwater flow in the permeable carbonate unit, whereas most of the obtained heat-flow data may reflect the deep, undisturbed, conductive thermal regime.
In this paper we develop a model of the ground deformation behaviour occurred at Ischia Island (S... more In this paper we develop a model of the ground deformation behaviour occurred at Ischia Island (Southern Italy) in the 1992-2010 time period. The model is employed to investigate the forces and physical parameters of the crust controlling the subsidence of the Island. To this aim, we integrate and homogenize in a Finite Element (FE) environment a large amount of data derived from several and different observation techniques (i.e., geological, geophysical and remote sensing). In detail, the main steps of the multiphysics model are: (i) the generation of a 3D geological model of the crust beneath the Island by merging the available geological and geophysical information; (ii) the optimization of a 3D thermal model by exploiting the thermal measurements available in literature; (iii) the definition of the 3D Brittle/Ductile transition by using the temperature distribution of the crust and the physical information of the rocks; (iv) the optimization of the ground deformation velocity model (that takes into account the rheological stratification) by considering the spatial and temporal information detected via satellite multi-orbit C-Band SAR (Synthetic Aperture Radar) measurements acquired during the 1992-2010 time period. The achieved results allow investigating the physical process responsible for the observed ground deformation pattern. In particular, they reveal how the rheology modulates the spatial and temporal evolution of the long-term subsidence phenomenon, highlighting a coupling effect of the viscosities of the rocks and the gravitational loading of the volcano edifice. Moreover, the achieved results provide a very detailed and realistic velocity field image of the subsurface crust of the Ischia Island Volcano.
We present an analysis on thermal properties, density and porosity of clastic, chemical/biochemic... more We present an analysis on thermal properties, density and porosity of clastic, chemical/biochemical and intrasedimentary volcanic rocks collected from petroleum exploration wells of the Po Basin (Northern Italy). Moreover, we investigate the applicability of the Hashin-Shtrikman's model for a mineral aggregate in combination with the Zimmerman's model that takes pore shape into account, to calculate the bulk thermal conductivity. In case of macroscopically isotropic rocks, deviations between predicted and measured values range from −2.2 per cent to 6.9 per cent, and significantly decrease if a proper pore aspect ratio is chosen. Regarding the volumetric heat capacity, approximate estimates were obtained by means of a weighted average of the volumetric heat capacity of the mineral grains and that of the pore-filling water. The differences between the computed and measured values range from -6.2 per cent to 4.9 per cent and, on average, the computed volumetric heat capacity is lower by 1.6 per cent. The water loss during compaction and the temperature increase with depth are main factors controlling thermal properties. An anisotropy effect occurs in the case of rocks rich in sheet silicates. Due to rotation of these minerals, the vertical thermal conductivity of sheet silicates decreases exponentially with burial depth from 2.13 W m −1 K −1 at the surface to 0.52 W m −1 K −1 at 4.5 km. The laboratory data allow the formulation of compaction curves for the different sedimentary rock types. Examples of estimations of in situ vertical thermal conductivity and heat flow are finally given for two petroleum wells at which lithostratigraphic information is known in good detail.
A revised surface heat flow map of a sector of the Northern Apennines is presented, constrained b... more A revised surface heat flow map of a sector of the Northern Apennines is presented, constrained by recently available thermal and petrophysical logs from 174 wells drilled for geothermal and hydrocarbon exploration purposes. The borehole temperatures have been corrected for drilling, inclination, and palaeoclimate effects. The corrected temperature data, combined with petrophysical parameters for each individual formation, have been used to derive shallow geotherms (down to a maximum depth of 8 km), which have yielded site-specific heat flow values. These values, once corrected for palaeoclimatic topographic and erosion/sedimentation effects, have been contoured by a kriging procedure to obtain the heat flow map.
On the basis of lithostratigraphic data from petroleum wells, geophysical logs and laboratory mea... more On the basis of lithostratigraphic data from petroleum wells, geophysical logs and laboratory measurements, we revised surface heat-flow values from previous studies and obtained new data for the western sector of the Po Basin (Italy). The available bottom-hole temperatures were corrected for mud circulation. The in situ thermal conductivity was estimated by taking into account the combined effects of mineral composition, anisotropy, temperature and porosity. The radiogenic heat of the basin rocks was evaluated from natural γ -ray logs and with laboratory γ -ray spectrometry. After correction for sedimentation and palaeoclimate influences, the inferred surface heat flow of the basin is 73 ± 4 mW m −2 in the undeformed Po foredeep and decreases to 64 ± 6 mW m −2 in the Alps and Apennines buried units, affected by active thrust. Numerical and analytical calculations indicate that such a decrease is likely caused by thrusting. Local heat flow minima (<60 mW m −2 ) may be related to groundwater movement. These data together with those available for the surrounding orogenic belts allow redrawing the heat-flow pattern of northwestern Italy.
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand -outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
A B S T R A C T Low-to-medium temperature fluid reservoirs hosted in carbonate rocks are some of ... more A B S T R A C T Low-to-medium temperature fluid reservoirs hosted in carbonate rocks are some of the most promising and unknown geothermal systems. Western Sicily is considered a key exploration area. This paper illustrate a multidisciplinary and integrated review of the existing geological, geochemical and geophysical data, mainly acquired during oil and gas explorations since the 1950s, specifically re-analyzed for geothermal purposes, has led to understanding the western Sicily geothermal system as a whole, and to reconstructing the modalities and particular features of the deep fluid circulation within the regional reservoir. The data review suggests the presence of wide groundwater flow systems in the reservoir beneath impervious cap rocks. We identified the main recharge areas, reconstructed the temperature distribution at depth, recognized zones of convective geothermal flow, and depicted the main geothermal fluid flow paths within the reservoir. We believe that our reconstruction of geothermal fluid circulation is an example of the general behavior of low-to-medium enthalpy geothermal systems hosted in carbonate units on a regional scale. Due to the recent technological developments of binary plants, these systems have become more profitable, not only for geothermal direct uses but also for power production.
In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences... more In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences and Earth Resources (CNR-IGG) and sponsored by the Ministry of Economic Development (MiSE), dedicated to the evaluation of geothermal potential in the regions of the Convergence Objective in Italy (Puglia, Calabria, Campania and Sicily), is expected to evaluate the ability of the territory to heat exchange with the ground for air conditioning of buildings. To identify the conditions for the development of low enthalpy geothermal systems collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a synergistic and simplified way the physical parameters (geological, lithostratigraphic, hydrogeological, thermodynamic) that most influence the subsoil behavior for thermal exchange. The litho-stratigraphic and hydrogeological database created for every region led to the production of different cartographic thematic maps, such as the thermal conductivity (lithological and stratigraphical), the surface geothermal flux, the average annual temperature of air, the climate zoning, the areas of hydrogeological restrictions. To obtain a single representation of the geo-exchange potential of the region, the different thematic maps described must be combined together by means of an algorithm, defined on the basis of the SINTACS methodology. The purpose is to weigh the contributions of the involved parameters and to produce a preliminary synthesis map able to identify the territorial use of geothermal heat pump systems, based on the geological characteristics and in agreement with the existing regulatory constraints.
We revised the concept of convective, intrusive geothermal plays, considering that the tectonic s... more We revised the concept of convective, intrusive geothermal plays, considering that the tectonic setting is not, in our opinion, a discriminant parameter suitable for a classification. We analysed and compared four case studies: (i) Larderello (Italy), (ii) Mt Amiata (Italy), (iii) The Geysers (USA) and (iv) Kizildere (Turkey). The tectonic settings of these geothermal systems are different and a matter of debate, so it is hard to use this parameter, and the results of classification are ambiguous. We suggest a classification based on the age and nature of the heat source and the related hydrothermal circulation. Finally we propose to distinguish the convective geothermal plays as volcanic, young intrusive and amagmatic.
In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences... more In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences and Earth Resources (CNR-IGG) and sponsored by the Ministry of Economic Development (MiSE), dedicated to the evaluation of geothermal potential in the regions of the Convergence Objective in Italy (Puglia, Calabria, Campania and Sicily), is expected to evaluate the ability of the territory to heat exchange with the ground for air conditioning of buildings. To identify the conditions for the development of low enthalpy geothermal systems have been collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a synergistic and simplified way the physical parameters (geological, lithostratigraphic, hydrogeological, thermodynamic) that most influence the subsoil behavior for thermal exchange. The litho-stratigraphic and hydrogeological database created for every region led to the production of di...
Geothermal deep closed-loop heat exchangers: A novel technical potential evaluation to answer the power and heat demands, 2022
This paper investigates and optimises the thermal performance of deep closed-loop heat exchanger ... more This paper investigates and optimises the thermal performance of deep closed-loop heat exchanger (DCHE) systems by applying a computational numerical approach. The investigated DCHE configuration accounts for two deep vertical boreholes, an injection and a production well, connected by a horizontal borehole at depth and an insulated pipeline at the surface, establishing an effective closed-loop system. First, a parametric sensitivity study explores the effects of the environmental, design and operating variables on the production temperature. The simulation uses realistic geological and geothermal conditions, depths, circulation rates and injection temperatures. Two complex numerical models are then solved for site-specific DCHEs in different geological scenarios: a foreland basin and a convergent margin hosting low-to-intermediate and high-temperature geothermal resources, respectively. Production temperatures beyond 40-60°C and 100°C, sustainable for both heat and electric power generation, are obtained, depending on the geothermal conditions and closed-loop dimensions. Furthermore, circulation rates of 0.02-0.04 m 3 s − 1 are cost-effective, and the system's efficiency and sustainability increase when a fluctuating and periodic heat extraction strategy is employed. When efficiently operated, DCHEs are a viable solution for renewable energy production and should be integrated into the local heat market and distribution network infrastructure.
This paper describes a data integration tool used to identify potentially undiscovered geothermal... more This paper describes a data integration tool used to identify potentially undiscovered geothermal resources in the island of Sicily. The factors facilitating the recovery of exploitable geothermal energy were defined, and their spatial correlation established by Geographic Information System (GIS) models. By prioritizing favourable conditions using an Index Overly method, "favourability" maps of Sicily were obtained. The maps considered both geological and economic aspects, and energy recovery was considered for current technologies. Our approach and maps are useful for developing and planning local or national energy policies including geothermal energy.
The growing interest on renewable energy sources is stimulating new efforts aimed at the assessme... more The growing interest on renewable energy sources is stimulating new efforts aimed at the assessment of geothermal potential in several countries, and new developments are expected in the near future. In this framework, a basic step forward is to focus geothermal investigations on geological environments which so far have been relatively neglected. Some intracontinental sedimentary basins could reveal important low enthalpy resources. The evaluation of the geothermal potential in such geological contexts involves the synergic use of geophysical and hydrogeological methodologies.
&amp;lt;p&amp;gt;Based on a joint analysis of geothermal indicators (e.g. temperature map... more &amp;lt;p&amp;gt;Based on a joint analysis of geothermal indicators (e.g. temperature map at different depth, surface heat flux) and practical features (e.g. restricted areas, existing research lease), two promising areas in southern Tuscany were identified to perform a more detailed geothermal resource characterization. An area is located on the north-east of the Larderello-Travale geothermal field, and the other one is located on the west of the Mt. Amiata geothermal field.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;A quantitative geothermal resources assessment was performed in the aforementioned areas of Tuscany by solving numerical thermo-fluid dynamic models and by computing the geothermal potential using the &amp;amp;#8216;ThermoGIS&amp;amp;#8217; software, as further developed for the Italian case (Trumpy et al., 2016).&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;First of all, geological and geophysical data required for geological and thermo-fluid dynamic modelling were collected and organised. The geological data were used to build a 3D geological model of the two areas of interest suitable for numerical simulations. Static temperature data gathered from the Italian National Geothermal Database together with site-specific heat flow measurements were used to calibrate the simulated steady state temperature distribution.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;The geothermal potential computed by integrating geological, thermal and petro-physical information implementing the volume method used in ThermoGIS provided estimates of the heat in place and the geothermal technical potential maps. The resulting technical potential in the area close to Larderello &amp;amp;#8211;Travale is 330 MW&amp;lt;sub&amp;gt;e&amp;lt;/sub&amp;gt; and in the Mt. Amiata sector is 50MW&amp;lt;sub&amp;gt;e&amp;lt;/sub&amp;gt;.&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;References&amp;lt;/p&amp;gt; &amp;lt;p&amp;gt;Trumpy E., Botteghi S., Caiozzi F., Donato A., Gola G., Montanari D., Pluymaekers M., Santilano A., Van Wees, J.D., Manzella A. Geothermal potential assessment for a low carbon strategy: a new systematic approach applied in southern Italy. Energy 103, 167-181, 2016.&amp;lt;/p&amp;gt;
International Journal of Terrestrial Heat Flow and Applications
We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m de... more We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m depth range to unravel thermal regime beneath the central-northern Apennines chain and the surrounding sedimentary basins. We particularly selected deepest bottom hole temperatures, all recorded within the permeable carbonate Paleogene-Mesozoic formations, which represent the most widespread tectono-stratigraphic unit of the study area. The available temperatures were corrected for the drilling disturbanceand the thermal conductivity was estimated from detailed litho-stratigraphic information and by taking into account the pressure and temperature effect. The thermal resistance approach, including also the radiogenic heat production, was used to infer the terrestrial heat flow and to highlight possible advective perturbation due to groundwater circulation. Only two boreholes close to recharge areas argue for deep groundwater flow in the permeable carbonate unit, whereas most of the obtaine...
This paper describes a data integration tool used to identify potentially undiscovered geothermal... more This paper describes a data integration tool used to identify potentially undiscovered geothermal resources in the island of Sicily. The factors facilitating the recovery of exploitable geothermal energy were defined, and their spatial correlation established by Geographic Information System (GIS) models.
We exploit the concept of the geothermal favourability, widely used for hydrothermal and EGS syst... more 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.
We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m de... more We analyzed thermal data from deep oil exploration and geothermal boreholes in the 1000-7000 m depth range to unravel thermal regime beneath the central-northern Apennines chain and the surrounding sedimentary basins. We particularly selected deepest bottom hole temperatures, all recorded within the permeable carbonate Paleogene-Mesozoic formations, which represent the most widespread tectono-stratigraphic unit of the study area. The available temperatures were corrected for the drilling disturbance and the thermal conductivity was estimated from detailed litho-stratigraphic information and by taking into account the pressure and temperature effect. The thermal resistance approach, including also the radiogenic heat production, was used to infer the terrestrial heat flow and to highlight possible advective perturbation due to groundwater circulation. Only two boreholes close to recharge areas argue for deep groundwater flow in the permeable carbonate unit, whereas most of the obtained heat-flow data may reflect the deep, undisturbed, conductive thermal regime.
In this paper we develop a model of the ground deformation behaviour occurred at Ischia Island (S... more In this paper we develop a model of the ground deformation behaviour occurred at Ischia Island (Southern Italy) in the 1992-2010 time period. The model is employed to investigate the forces and physical parameters of the crust controlling the subsidence of the Island. To this aim, we integrate and homogenize in a Finite Element (FE) environment a large amount of data derived from several and different observation techniques (i.e., geological, geophysical and remote sensing). In detail, the main steps of the multiphysics model are: (i) the generation of a 3D geological model of the crust beneath the Island by merging the available geological and geophysical information; (ii) the optimization of a 3D thermal model by exploiting the thermal measurements available in literature; (iii) the definition of the 3D Brittle/Ductile transition by using the temperature distribution of the crust and the physical information of the rocks; (iv) the optimization of the ground deformation velocity model (that takes into account the rheological stratification) by considering the spatial and temporal information detected via satellite multi-orbit C-Band SAR (Synthetic Aperture Radar) measurements acquired during the 1992-2010 time period. The achieved results allow investigating the physical process responsible for the observed ground deformation pattern. In particular, they reveal how the rheology modulates the spatial and temporal evolution of the long-term subsidence phenomenon, highlighting a coupling effect of the viscosities of the rocks and the gravitational loading of the volcano edifice. Moreover, the achieved results provide a very detailed and realistic velocity field image of the subsurface crust of the Ischia Island Volcano.
We present an analysis on thermal properties, density and porosity of clastic, chemical/biochemic... more We present an analysis on thermal properties, density and porosity of clastic, chemical/biochemical and intrasedimentary volcanic rocks collected from petroleum exploration wells of the Po Basin (Northern Italy). Moreover, we investigate the applicability of the Hashin-Shtrikman's model for a mineral aggregate in combination with the Zimmerman's model that takes pore shape into account, to calculate the bulk thermal conductivity. In case of macroscopically isotropic rocks, deviations between predicted and measured values range from −2.2 per cent to 6.9 per cent, and significantly decrease if a proper pore aspect ratio is chosen. Regarding the volumetric heat capacity, approximate estimates were obtained by means of a weighted average of the volumetric heat capacity of the mineral grains and that of the pore-filling water. The differences between the computed and measured values range from -6.2 per cent to 4.9 per cent and, on average, the computed volumetric heat capacity is lower by 1.6 per cent. The water loss during compaction and the temperature increase with depth are main factors controlling thermal properties. An anisotropy effect occurs in the case of rocks rich in sheet silicates. Due to rotation of these minerals, the vertical thermal conductivity of sheet silicates decreases exponentially with burial depth from 2.13 W m −1 K −1 at the surface to 0.52 W m −1 K −1 at 4.5 km. The laboratory data allow the formulation of compaction curves for the different sedimentary rock types. Examples of estimations of in situ vertical thermal conductivity and heat flow are finally given for two petroleum wells at which lithostratigraphic information is known in good detail.
A revised surface heat flow map of a sector of the Northern Apennines is presented, constrained b... more A revised surface heat flow map of a sector of the Northern Apennines is presented, constrained by recently available thermal and petrophysical logs from 174 wells drilled for geothermal and hydrocarbon exploration purposes. The borehole temperatures have been corrected for drilling, inclination, and palaeoclimate effects. The corrected temperature data, combined with petrophysical parameters for each individual formation, have been used to derive shallow geotherms (down to a maximum depth of 8 km), which have yielded site-specific heat flow values. These values, once corrected for palaeoclimatic topographic and erosion/sedimentation effects, have been contoured by a kriging procedure to obtain the heat flow map.
On the basis of lithostratigraphic data from petroleum wells, geophysical logs and laboratory mea... more On the basis of lithostratigraphic data from petroleum wells, geophysical logs and laboratory measurements, we revised surface heat-flow values from previous studies and obtained new data for the western sector of the Po Basin (Italy). The available bottom-hole temperatures were corrected for mud circulation. The in situ thermal conductivity was estimated by taking into account the combined effects of mineral composition, anisotropy, temperature and porosity. The radiogenic heat of the basin rocks was evaluated from natural γ -ray logs and with laboratory γ -ray spectrometry. After correction for sedimentation and palaeoclimate influences, the inferred surface heat flow of the basin is 73 ± 4 mW m −2 in the undeformed Po foredeep and decreases to 64 ± 6 mW m −2 in the Alps and Apennines buried units, affected by active thrust. Numerical and analytical calculations indicate that such a decrease is likely caused by thrusting. Local heat flow minima (<60 mW m −2 ) may be related to groundwater movement. These data together with those available for the surrounding orogenic belts allow redrawing the heat-flow pattern of northwestern Italy.
District heating networks are commonly addressed in the literature as one of the most effective s... more District heating networks are commonly addressed in the literature as one of the most effective solutions for decreasing the greenhouse gas emissions from the building sector. These systems require high investments which are returned through the heat sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, prolonging the investment return period. The main scope of this paper is to assess the feasibility of using the heat demand -outdoor temperature function for heat demand forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 buildings that vary in both construction period and typology. Three weather scenarios (low, medium, high) and three district renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. The results showed that when only weather change is considered, the margin of error could be acceptable for some applications (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation scenarios, the error value increased up to 59.5% (depending on the weather and renovation scenarios combination considered). The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and renovation scenarios considered). On the other hand, function intercept increased for 7.8-12.7% per decade (depending on the coupled scenarios). The values suggested could be used to modify the function parameters for the scenarios considered, and improve the accuracy of heat demand estimations.
A B S T R A C T Low-to-medium temperature fluid reservoirs hosted in carbonate rocks are some of ... more A B S T R A C T Low-to-medium temperature fluid reservoirs hosted in carbonate rocks are some of the most promising and unknown geothermal systems. Western Sicily is considered a key exploration area. This paper illustrate a multidisciplinary and integrated review of the existing geological, geochemical and geophysical data, mainly acquired during oil and gas explorations since the 1950s, specifically re-analyzed for geothermal purposes, has led to understanding the western Sicily geothermal system as a whole, and to reconstructing the modalities and particular features of the deep fluid circulation within the regional reservoir. The data review suggests the presence of wide groundwater flow systems in the reservoir beneath impervious cap rocks. We identified the main recharge areas, reconstructed the temperature distribution at depth, recognized zones of convective geothermal flow, and depicted the main geothermal fluid flow paths within the reservoir. We believe that our reconstruction of geothermal fluid circulation is an example of the general behavior of low-to-medium enthalpy geothermal systems hosted in carbonate units on a regional scale. Due to the recent technological developments of binary plants, these systems have become more profitable, not only for geothermal direct uses but also for power production.
In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences... more In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences and Earth Resources (CNR-IGG) and sponsored by the Ministry of Economic Development (MiSE), dedicated to the evaluation of geothermal potential in the regions of the Convergence Objective in Italy (Puglia, Calabria, Campania and Sicily), is expected to evaluate the ability of the territory to heat exchange with the ground for air conditioning of buildings. To identify the conditions for the development of low enthalpy geothermal systems collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a synergistic and simplified way the physical parameters (geological, lithostratigraphic, hydrogeological, thermodynamic) that most influence the subsoil behavior for thermal exchange. The litho-stratigraphic and hydrogeological database created for every region led to the production of different cartographic thematic maps, such as the thermal conductivity (lithological and stratigraphical), the surface geothermal flux, the average annual temperature of air, the climate zoning, the areas of hydrogeological restrictions. To obtain a single representation of the geo-exchange potential of the region, the different thematic maps described must be combined together by means of an algorithm, defined on the basis of the SINTACS methodology. The purpose is to weigh the contributions of the involved parameters and to produce a preliminary synthesis map able to identify the territorial use of geothermal heat pump systems, based on the geological characteristics and in agreement with the existing regulatory constraints.
We revised the concept of convective, intrusive geothermal plays, considering that the tectonic s... more We revised the concept of convective, intrusive geothermal plays, considering that the tectonic setting is not, in our opinion, a discriminant parameter suitable for a classification. We analysed and compared four case studies: (i) Larderello (Italy), (ii) Mt Amiata (Italy), (iii) The Geysers (USA) and (iv) Kizildere (Turkey). The tectonic settings of these geothermal systems are different and a matter of debate, so it is hard to use this parameter, and the results of classification are ambiguous. We suggest a classification based on the age and nature of the heat source and the related hydrothermal circulation. Finally we propose to distinguish the convective geothermal plays as volcanic, young intrusive and amagmatic.
In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences... more In the framework of VIGOR Project, a national project coordinated by the Institute of Geosciences and Earth Resources (CNR-IGG) and sponsored by the Ministry of Economic Development (MiSE), dedicated to the evaluation of geothermal potential in the regions of the Convergence Objective in Italy (Puglia, Calabria, Campania and Sicily), is expected to evaluate the ability of the territory to heat exchange with the ground for air conditioning of buildings. To identify the conditions for the development of low enthalpy geothermal systems have been collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a synergistic and simplified way the physical parameters (geological, lithostratigraphic, hydrogeological, thermodynamic) that most influence the subsoil behavior for thermal exchange. The litho-stratigraphic and hydrogeological database created for every region led to the production of di...
A key requirement for a further production of geothermal energy, by increasing the number of proj... more A key requirement for a further production of geothermal energy, by increasing the number of projects as well as the variety of uses, is to clearly identify and rank resources and opportunities. In this work we provide a practical analytical framework for the systematic capture of information relevant to the assessment of the geothermal resources of Sicily (mainland). Any geothermal assessment necessitates an extensive search of the existing data. In Italy the most relevant existing information regarding the geothermal resources includes temperature data measured in oil and gas exploration boreholes and physical and chemical data from wells and natural thermal springs. [...]
Within more or less karstifed carbonates, fractures generally play an important role both in chan... more Within more or less karstifed carbonates, fractures generally play an important role both in channelling the geothermal fluid flow and in the hot water storage, making limestones and dolostones among the more important potential geothermal reservoirs, worldwide. Carbonate rocks constitute the backbone of the Italian Apennines that have to be considered as natural laboratories for the key study of these geothermal systems, and this is particularly true in the case of western Sicily. A multidisciplinary and integrated review of existing geological, geophysical, geochemical and thermometric data (mainly acquired during oil exploration), specifically reread for geothermal purposes, and the integration with new data acquired in particular key areas, such as the Mazara del Vallo site in the southern part of western Sicily, allowed us to better understand this -regional scale- medium-enthalpy geothermal system characterised by measured temperatures up to 100 °C. The interpretation of data also allowed to reconstruct different modalities and peculiarities of fluids circulation at shallow crustal levels, and to evaluate the geothermal potentialities of western Sicily, in general. We suggest that these findings could be taken as exemplificative of the behaviour of low-to medium enthalpy geothermal systems hosted in carbonate units that, also due to the recent technological developments in the geothermic exploitation of low-enthalpy fluids become even more interesting both for direct uses applications and power production with the new generation of binary power plants.
In the frame of the " Geothermal Atlas for Southern Italy " Project, a detailed 3D geological, t... more In the frame of the " Geothermal Atlas for Southern Italy " Project, a detailed 3D geological, thermal and rheological model of Ischia Island was built by integrating geological, geophysical and geochemical data. A critical review of publicly available data allowed us to organize a complete dataset in Petrel (Schlumberger) environment for the 3D geological modelling. The geological maps, well data and several geophysical data were used to constrain the shallow region of the model from the youngest deposits to the tuff rocks of the St. Nicola Synthem and the deposits of Ancient Ischia (for detail on stratigraphy see, Ispra web site 2015). Seismic data were used to constrain the deeper level of the Ischia Island up to the Meso-Cenozoic Carbonate rocks (Finetti & Morelli, 1974). Moreover, in order to implement the thermal and rheological analysis, we modeled the deeper surfaces of crystalline basement and Mohorovičić discontinuity based on previous studies in literature. In the second step, we performed a 3D numerical modelling of thermal field by using the a priori geological and geophysical information and by consideration of thermo-hydraulic properties including internal heat production and mechanical heterogeneities of the crust beneath the volcanic island. We solved, in a numerical context, the heat and fluid transport equation in a conductive/convective steady-state regime. We simulated the effects on the thermal field of a laccolith intrusion at shallow level in the crust (Paoletti et al., 2009). Subsequently, a parameters optimization procedure was applied to minimize the difference between the computed and measured temperature data. Finally, the thermal model was used as a priori information to image the 3D rheological stratification of the shallow crust beneath the volcanic Island of Ischia in order to understand the mechanical behavior of the crust in this area. As result of our study, we proposed the 3D geometry of the Brittle/Ductile transition, calculated numerically, for the active volcano of Ischia Island. The thermal field in the geothermal reservoir has also been figured out.
The assessment of geothermal potential and the mapping of suitability for different geothermal us... more The assessment of geothermal potential and the mapping of suitability for different geothermal uses are of relevance for deciding strategies regarding the eventual geothermal exploitation. The VIGOR project in southern Italy, founded by the Italian Ministry of Economic Development falls within this context, since one of main targets is the assessment of geothermal potential both at local and regional scale. Under this context, a new methodology has been optimized for geothermal potential assessment in collaboration with the Geological Survey of the Netherlands (TNO). The regional geothermal potential evaluation has the main purpose: i) to assess the resource up to 5000 m depth, therefore ii) to identify and locate the main potential reservoir, iii) to estimate the amount of heat in place and eventually the energy produced on the basis of the resource and the applications to be developed (e.g., power production by binary plant, type of direct use and co-heat). The procedure designed for the VIGOR project has been called VIGORThermoGIS, which is an implementation of the ThermoGIS TNO code, on its turn based on a three dimensional model discretised into a regular grid, spaced by a 1000 m side and by 100 m depth. For each cell the Heat In Place and Technical Potential are calculated, then the grid maps representing the bast place for a specific kind of application, are extracted. The VIGOR ThermoGIS code is written in Java, and can be executed on any computer. The required input data are: i) the reservoir thickness, ii) the thermal model for the considered volume, iii) the permeability values of the reservoir, and iv) a set of thermo-petrophysical properties of the water-rock system. Nowadays, the obtained output maps for Sicily and Puglia regions are published into the VIGOR webGIS, whereas the potential maps for Campania and Calabria regions are on their way (will be available soon). Being the assessment of the regional geothermal resources for the VIGOR Project in the last stages of development, the already gathered results will allow to go towards the next step regarding the economic features, by introducing parameters such as: plant, operations and maintenance costs, project life cycles, taxation, interest rates on debs and feed-in tariffs.
With the exception of volcanic areas where geothermal reservoirs are generally developed within p... more With the exception of volcanic areas where geothermal reservoirs are generally developed within permeable volcanic horizons, deep carbonate aquifers host probably the most important world geothermal resources. Although some cases of exploitation of this carbonate reservoirs are already effective both for electric power generation and district heating, it is not yet clear how, on a regional scale, geothermal fluids circulate, determining the temperature distribution at depth. In our vision, Western Sicily could represent a key area to better define how fluids circulate within this kind of reservoirs. We present a review of geochemical, geological and geophysical data, mainly acquired from wells drilled during the oil exploration since the 50s, specifically reread for geothermal purposes, has allowed to understand the western Sicily geothermal system (Fancelli et al. 1991; Montanari et al. 2015; Trumpy et al. 2015) and to reconstruct the modalities and peculiarities of deep fluids circulation within the regional carbonate reservoir. Being the carbonate reservoir as thick as several km, it is affected by the upward of rising CO2-rich convective deep thermal waters, at several places even with marked 3 He/ 4 He anomalies, such as in the area of Sciacca, where high-enthalpy systems at relatively shallow depth are possibly located off shore in the Sicily channel. In the remaining areas several structural highs of the carbonates, buried by impermeable flysch units and Neogene clay-rich sediments, likely host fluids with temperatures up to 100 °C at relatively shallow depths, locally affected by convective fluid circulation. The proposed reconstruction of geothermal fluids circulation on a regional scale could be taken as exemplificative of the general behavior of low-to-medium enthalpy geothermal systems hosted in carbonate units that, due to the recent technological developments of binary plants, have become more profitable, not only for direct uses but even for power production.
The multidisciplinary and integrated review of existing data (mainly acquired during oil explora... more The multidisciplinary and integrated review of existing data (mainly acquired during oil exploration), specifically reread for geothermal purposes, and the integration with new data acquired in particular key areas, such as the Mazara Del Vallo site in the southern part of western Sicily, allowed us to better understand this -regional scale- medium-enthalpy geothermal system (with measured temperatures up to 100 °C), to reconstruct the modalities and peculiarities of fluids circulation, and to evaluate the geothermal potentialities of western Sicily. We suggest that these findings could be taken as exemplificative of the behavior of low-to medium enthalpy geothermal systems hosted in carbonate units, that also due to recent technological developments become even more interesting both for direct uses applications and power production.
Oil exploration in western Sicily started in the late 1950s when several exploration wells were d... more Oil exploration in western Sicily started in the late 1950s when several exploration wells were drilled, and continued with the acquisition of many seismic reflection profiles and the drilling of new wells in the1980s. The geological interpretation of these data mainly provided new insights for the definition of geometric relationships between tectonic units and structural reconstruction at depth. Although it has not produced completely satisfactory results for oil industry, this hydrocarbon exploration provided a great amount of data, resulting very suitable for geothermal resource assessment. From a geothermal point of view western Sicily is, indeed, a very promising area, with the manifestation at surface of several thermal springs, localized areas of high heat flux and thick carbonates units uninterruptedly developing from surface up top great depths. These available data were often collected with the modalities and purposes typical of oil exploration, not always the finest for geothermal exploration as in the case of temperature measurements. The multidisciplinary and integrated review of these data, specifically corrected for geothermal purposes, and the integration with new data acquired in particular key areas such as the Mazara Del Vallo site in the southern part of western Sicily, allowed us to better understand this medium-enthalpy geothermal system, to reconstruct the modalities and peculiarities of fluids circulation, and to evaluate the geothermal potentialities of western Sicily. We suggest that western Sicily can be taken as a reference for the understanding of geothermal systems developed at a regional scale within carbonate rocks. This study was performed within the framework of the VIGOR project (http://www.vigor-geotermia.it).
A performance assessment of deep-seated geothermal systems was carried out in collaboration with ... more A performance assessment of deep-seated geothermal systems was carried out in collaboration with TNO (Netherlands Geological Survey) to evaluate at regional scale the geothermal energy potential of the VIGOR Project regions (Southern Italy). Three main components were considered in the analysis: the resource -estimating its magnitude and distribution, the technology -establishing requirements for extracting and utilizing energy from reservoir including the application to be developed and the economics -estimating costs per unit of power produced. The VigorThermoGIS code, based on the volumetric estimation method and Monte Carlo simulations, provided probabilistic estimates of the stored heat, theoretical technical potential and economic technical potential. The results for the Sicily Region are here presented.
(1200m b.s.l.), the medium-high enthalpy of the system (145°C at the top of the reservoir) and th... more (1200m b.s.l.), the medium-high enthalpy of the system (145°C at the top of the reservoir) and the presence of water and steam, as recorded by ENEL reports, allowed a preliminary individuation, at the culmination of the carbonatic ridge, of the shallowest resource to be considered for future exploitation.
L’Italia, da sempre protagonista nel settore geotermico, si propone di mantenere una posizione di... more L’Italia, da sempre protagonista nel settore geotermico, si propone di mantenere una posizione di tutto rispetto investendo in ricerca e ottimizzando la gestione dei sistemi energetici. La Legge Sviluppo n. 99/09 è stato l’atto di forza che ha dato nuova linfa portando allo sviluppo di progetti pilota. Il presente volume racchiude una parte dei contributi presentati al convegno, organizzato presso la Facoltà di Ingegneria Civile e Industriale dell’Università La Sapienza di Roma, sulla definizione e sulle modalità di utilizzo dei sistemi geotermici non convenzionali, il cui uso richiede l’impiego di metodi e tecnologie innovativi non del tutto mature dal punto di vista commerciale.
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Papers by Gianluca Gola
To identify the conditions for the development of low enthalpy geothermal systems collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a synergistic and simplified way the physical parameters (geological, lithostratigraphic, hydrogeological, thermodynamic) that most influence the subsoil behavior
for thermal exchange.
The litho-stratigraphic and hydrogeological database created for every region led to the production of different cartographic thematic maps, such as the thermal conductivity (lithological and stratigraphical), the surface geothermal flux, the average annual temperature of air, the climate zoning, the areas of hydrogeological restrictions.
To obtain a single representation of the geo-exchange potential of the region, the different thematic maps described must be combined together by means of an algorithm, defined on the basis of the SINTACS methodology. The purpose is to weigh the contributions of the involved parameters and to produce a preliminary synthesis map able
to identify the territorial use of geothermal heat pump systems, based on the geological characteristics and in agreement with the existing regulatory constraints.
The tectonic settings of these geothermal systems are different and a matter of debate, so it is hard to use this
parameter, and the results of classification are ambiguous. We suggest a classification based on the age and nature
of the heat source and the related hydrothermal circulation. Finally we propose to distinguish the convective geothermal plays as volcanic, young intrusive and amagmatic.
To identify the conditions for the development of low enthalpy geothermal systems collected and organized on a regional scale geological and stratigraphic data useful for the preparation of a specific thematic mapping, able to represent in a synergistic and simplified way the physical parameters (geological, lithostratigraphic, hydrogeological, thermodynamic) that most influence the subsoil behavior
for thermal exchange.
The litho-stratigraphic and hydrogeological database created for every region led to the production of different cartographic thematic maps, such as the thermal conductivity (lithological and stratigraphical), the surface geothermal flux, the average annual temperature of air, the climate zoning, the areas of hydrogeological restrictions.
To obtain a single representation of the geo-exchange potential of the region, the different thematic maps described must be combined together by means of an algorithm, defined on the basis of the SINTACS methodology. The purpose is to weigh the contributions of the involved parameters and to produce a preliminary synthesis map able
to identify the territorial use of geothermal heat pump systems, based on the geological characteristics and in agreement with the existing regulatory constraints.
The tectonic settings of these geothermal systems are different and a matter of debate, so it is hard to use this
parameter, and the results of classification are ambiguous. We suggest a classification based on the age and nature
of the heat source and the related hydrothermal circulation. Finally we propose to distinguish the convective geothermal plays as volcanic, young intrusive and amagmatic.