Data integration and conceptual modelling of the Larderello geothermal area, Italy

Gola, Gianluca; Bertini, G.; Bonini, Marco; Botteghi, S.; Brogi, Andrea; Franco, R. de; Dini, Andréa; Donato, Assunta; Gianelli, Giovanni; Liotta, Domenico; Manzella, Adele; Montanari, Domenico; Montegrossi, Giordano; Petracchini, Lorenzo; Ruggieri, Giovanni; Santilano, Alessandro; Scrocca, Davide; Trumpy, Eugenio

doi:10.1016/j.egypro.2017.08.201

Cited by 32 publications

(27 citation statements)

References 21 publications

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“…Regarding the size, the estimated horizontal axis length of the pluton (14 km) is in agreement both with the width proposed by Mongelli et al (1998), on the basis of the magnetotelluric data (Fiordelisi et al, 1995), and compatible with the dimension of the pluton deduced from the geological cross-sections published by . The estimated age of emplacement of the magmatic body (300 kyr) is in agreement with the model estimates of Mongelli et al (1998) and Gola et al (2017) and turns out to be comparable with the age estimated for the volcanic activity of the neighbouring Mt. Amiata (Dini et al, 2005).…”

Section: Discussionsupporting

confidence: 79%

Regional thermo-rheological field related to granite emplacement in the upper crust: implications for the Larderello area (Tuscany, Italy)

2018

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We modelled thermo-rheological perturbations, related to the emplacement of a magmatic body in the upper crust. This approach was considered relevant for the areas characterized by elevated surface heat flow and chiefly for the geothermal fields. The numerical conductive thermal model applied to the Larderello geothermal area in Tuscany, allowed to constrain size, depth and timing of emplacement of the pluton. We inferred that the emplacement of a magmatic body, at a minimum depth of 3 km, having a horizontal extension of 14 km and a maximum thickness of 8 km, can reasonably reproduce the observed regional surface heat flow anomaly of the Larderello area, when 300 (± 100) kyr are elapsed from the magma emplacement. Even assuming an incremental growth, the first magma injection should not be older than 1 ± 0.3 Ma.Results of the thermal model were used to set up a rheological model and to simulate the drifting of the brittle-ductile transition during the cooling of the pluton. A comparison with the K-horizon profile, a prominent seismic reflector in the Larderello area, was then performed. It was found that the K-horizon approximately corresponds with the pluton roof and with the current location of the brittle-ductile transition.ARTICLE HISTORY

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Section: Discussionsupporting

confidence: 79%

Regional thermo-rheological field related to granite emplacement in the upper crust: implications for the Larderello area (Tuscany, Italy)

2018

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“…Early studies interpreted the K‐horizon as a brittle to ductile transition following the

450 \pm 50

°C isotherm (Batini et al, ; Liotta & Ranalli, ). The reflector was suggested to mimic the shape of the granitic intrusions at depth with no direct correlation with lithological discontinuities (Bertini et al, ; Gianelli et al, ; Gola et al, ; Piana Agostinetti et al, ). The drilling of the Venelle 2 reached 400 °C at 2,700 m depth (i.e., 200–300 m above the upper limit of the K‐horizon Bertani et al, ) pointing out that the isotherm marking the K‐horizon must hold higher values as suggested by the (suddenly) much higher temperatures encountered at 2,900 m depth (Bertani et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

Tectonic and Anthropogenic Microseismic Activity While Drilling Toward Supercritical Conditions in the Larderello‐Travale Geothermal Field, Italy

et al. 2020

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This study investigates the seismic activity occurring at the Larderello‐Travale geothermal field, central Italy, from June 2017 to January 2018. We deployed a network composed of nine broadband stations around the Venelle 2 well drilling for supercritical fluids. During the experiment, we recognize two types of seismic events (type 1 and type 2). Type‐1 events have clear P and S wave arrivals and occur in clusters both above and below the K‐horizon, which is a seismic reflector marking a debated transition zone at depth. The distribution and evolution of the seismic sequences suggest that the K‐horizon could be interpreted as a fluid‐rich region at near‐lithostatic pressures. Type‐2 events usually occur in swarms and show a periodic pattern, a narrow frequency band, and almost identical waveforms. Their source is estimated to be located near the well, and their occurrence ceases after about 3 weeks from the conclusion of the drilling. We propose a causal link with the drilling operations where pressure fronts inside the well may promote phase changes and fluid flow across the drilled formations. Our study sheds light on the fluid‐driven tectonic and anthropogenic seismic activity at the Larderello‐Travale geothermal field. More generally, we show that microseismic activity occurring during drilling in high‐pressure and high‐temperature conditions can remain at low magnitudes and that geothermal wells targeting geothermal fluids in such systems may be handled safely despite the critical conditions encountered at depth. The drilling of the Venelle 2 well is an encouraging example for the development of geothermal energy in critical conditions.

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“…With regards to the intrusive complex, granites have been cored in several deep wells and range in age from 3.8 to 1.3 Ma [45]. Accordingly, some interpretations of the deep structure of the Larderello geothermal field propose the presence of very large batholites (e.g., [10,11,46]), and data suggest a still active magmatic emplacement with a partial melt occurring at depth of a few kilometers (e.g., [12] and references therein).…”

Section: Geofluidsmentioning

confidence: 99%

“…We studied the Lago Boracifero sector of the Larderello geothermal field in Italy, where superheated steam is currently exploited from both a shallow reservoir in sedimentary units and a deep reservoir in crystalline rocks ( [7][8][9][10][11][12] and references therein). In the Larderello geothermal field, the presence of a deep and enigmatic seismic marker, the K-horizon, has long been identified [13] in both 2D and 3D seismic surveys.…”

Section: Introductionmentioning

confidence: 99%

Synthetic Seismic Reflection Modelling in a Supercritical Geothermal System: An Image of the K-Horizon in the Larderello Field (Italy)

et al. 2019

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We tested synthetic seismic reflection modelling along a seismic line (CROP-18A) in the geothermal field at Larderello (Italy). This seismic line is characterized by a discontinuous but locally very bright seismic marker, named K-horizon, which has been associated with various geological processes, including the presence of fluids at supercritical conditions. Geological and geophysical data were integrated in order to develop a 3D subsurface model of a portion of the Larderello field, where extremely high heat flow values have been recorded. In the study area, the K-horizon is particularly shallow and supercritical deep conditions were accessed at depth. The 2D model of the main geological units up to the K-horizon was extracted from the 3D model along the CROP-18A and used to generate the synthetic TWT stacked seismic sections which were then compared with the observed stacked CROP-18A seismic section. To build the synthetic sections, generated through the exploding reflector approach, a 2D velocity model was created assigning to each pixel of the model a constant P-wave velocity corresponding to the related geological unit. The geophysical parameters and the geological model reconstructions used in the modelling process derive from a multidisciplinary integration process including geological outcrop analogues, core samples, and geophysical and laboratory information. Two geophysical models were used to test the seismic response of the K-horizon, which is associated with (1) a lithological discontinuity or (2) a physically perturbed layer, represented by a randomized velocity distribution in a thin layer. For the latter geophysical model (i.e., the physically perturbed layer), we have tested three different scenarios changing the shape and the thickness of the modelled layer. Despite the reliable calibration implied by the use of homogeneous units, the seismic modelling clearly shows that the physically perturbed layer provides a better explanation of the reflectivity features associated with the K-horizon.

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Data integration and conceptual modelling of the Larderello geothermal area, Italy

Cited by 32 publications

References 21 publications

Regional thermo-rheological field related to granite emplacement in the upper crust: implications for the Larderello area (Tuscany, Italy)

Regional thermo-rheological field related to granite emplacement in the upper crust: implications for the Larderello area (Tuscany, Italy)

Tectonic and Anthropogenic Microseismic Activity While Drilling Toward Supercritical Conditions in the Larderello‐Travale Geothermal Field, Italy

Synthetic Seismic Reflection Modelling in a Supercritical Geothermal System: An Image of the K-Horizon in the Larderello Field (Italy)

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