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The EU H2020 GECO project is primarily aimed to set-up technologies to lower emissions from geothermal power generation by capturing them for either reuse or storage, to turn captured emissions in to commercial products and demonstrate the technical and economic feasibility of the injection method. To achieve this goal a site specific characterization and modelling of geology and geochemistry of the geothermal reservoir are in progress for optimization of the injection experiments at four distinct geothermal systems throughout Europe are in progress. The Italian GECO demonstration site is Castelnuovo, which is located in the northeaster side of the Larderello geothermal area and where Graziella Green Power and Storengy are planning to exploit a deep seated high temperature resource for power production with the scope of no non condensable gases (NCGs), release in atmosphere. The geothermal fluid will be extracted from 2 production wells and then it will be reinjected in the reservoir by mean of 1 reinjection well. A Zero emissions ORC power plant will produce 5MWe. For the geological assessment of Castelnuovo site an integrated methodology was designed and is applied to obtain the most reliable and accurate assessment of the site. The geological, reservoir and chemical reactive modelling are performed using field or labs data and observations (i.e., geology, geophysics, geochemistry surveys). Moreover, we adopted a double scale approach where regional, and larger, model was built to provide constrains to local, smaller and detailed, models. At regional scale a geological model including the main structures of the area is modelled to create the geometries needed to local models. At locale scale, firstly the thermal steady state of the rock volume and secondly the reinjection simulations on reservoir and fluids-rocks interaction during the reinjection are numerically computed.

We report the results of an experimental multianalytical characterisation of industrial cristobalite powders, used as raw materials for artificial stone production. Cristobalite is considered a serious threat to human health. The study was carried out through X-ray diffraction (XRD), scanning electron microscopy with energy dispersive microanalysis (SEM/EDS), continuous-wave (cw) and pulse electron paramagnetic resonance (EPR) spectroscopy. Our results point out a sub-micrometric size of the structural coherence in cristobalite, associated with numerous stacking defects. Moreover, the material was found characterised by the presence of superoxide radicals, whose persistence appears conceivably long. Radicals in a material synthesized through a high-temperature treatment were generated during the grinding step in the industrial production of cristobalite. During this process, in fact, both superoxide generation and structural defectivity are induced. Indeed, cristobalite powders already result activated by a radical population, before any kind of process in artificial stone production.

In this study, we carried out reactivation potential analysis of discontinuities revealed from four exploration boreholes penetrating heavily faulted and folded Upper Carboniferous rock strata of the Ruhr region. We performed this study based on the notion that slip is controlled by the ratio of shear to effective normal stresses acting on a pre-existing plane of weakness in the prevailing stress field configuration. The results of this analysis were supported by indicators of localized fluid flow, both on micro- and macro-scales, which confirm relationship between secondary permeability and in situ stress state in the Ruhr region. Findings from this study, in conjunction with results of destructive laboratory testing, indicate that the steep NW–SE- and NNE–SSW-striking planar discontinuities are likely to be either close to the critical state or critically stressed in the in situ stress configuration in the Ruhr region. These planar structures, as evidenced by indicators of localized permeability, are the main fluid pathways in the studied region. The NE–SW-striking discontinuities, on the other hand, are most likely to be closed and hydraulically inactive in the prevailing stress state. Based on results gained from this study, implications for utilization of deep geothermal energy in the region were discussed.

The Campi Flegrei geothermal system sets in one of the most famous and hazardous volcanic caldera in the world. The geothermal dynamics is suspected to have a crucial role in the monitored unrest phases and in the eruption triggering as well. Numerical models in the literature do not properly consider the geochemical effects of fluid-rock interaction into the hydrothermal circulation and this gap limits the wholly understanding of the dynamics. This paper focuses on fluid-rock interaction effects at the Campi Flegrei and presents relevant information requested for reactive transport simulations. In particular, we provide: (1) an extensive review of available data and new petrographic analyses of the San Vito cores rearranged in a conceptual model useful to define representative geochemical and petrophysical parameters of rock formations suitable for numerical simulations and (2) the implemented thermodynamic and kinetic data set calibrated for the San Vito 1 well area, central in the geothermal reservoir. A preliminary 0D-geochemical model, performed with a different contribution of CO2 at high (165 °C) and low (85 °C) temperatures, firstly allows reproducing the hydrothermal reactions over time of the Campanian Ignimbrite formation, the most important deposits in the case study area.

Studies on hydrothermal fluids circulation and tectonic structures improve the geothermal exploration and ex- ploitation in Iceland. In this paper we present the results of an integrated study (structural, kinematic, fluid inclu- sions analyses) carried out on a fossil and exhumed geothermal system at Geitafell (SE Iceland), considered an analogue of the active Krafla geothermal system (NE Iceland). Our work is addressed to the relationships be- tween the main structures and the paleo-geothermal fluids circulation at the boundary between the magma chamber (with magma of gabbroic composition) and host rocks, with the aim to get information on those factors having controlled the hydrothermal fluids flow, its storage and the rocks-fluid interaction, at 1-2 km crustal depth. The structural study is mostly based on defining the architecture of mineralized brittle shear zones, where, by measuring length and width of mineralized fractures, permeability was computed in 1.3 × 10-14 m2. As regards the hydrothermal paleo-fluids, fluid inclusions in hydrothermal quartz and calcite, usually associated with epidote and chlorite (i.e., the typical alteration minerals found in Icelandic geothermal fields), re- corded a fluid circulation with temperature ranging from about 255 °C to 320 °C, and boiling at the highest tem- perature. Transient pressure drop, likely related to fracture opening and propagation during tectonic activity, triggered local boiling process testified by fluid inclusions in a calcite sample. During a late evolution the system progressively cooled down to 60-90 °C. Paleo-geothermal fluids were characterized by low-salinity meteoric water, although higher salinity fluids (up to 10.6 wt% NaCl equiv.) entered in the system and mixed with mete- oric fluid. In the end, based on results from fluid inclusions, derived fluid density, permeability values and model- ing of viscosity, hydraulic conductivity between 2.8 × 10-8 to 1.8 × 10-7 m/s, was also computed within the fluids-channelling brittle shear zones. We finally encourage the key-study of fossil geothermal systems as a tool for getting parameters commonly obtained after drilling in active systems.

The aim of this work is to study the alteration of class G Cement at ambient temperature under a relatively high CO2 partial pressure through suitably designed laboratory experiments, in which cement hydration and carbonation are taken into account separately. First, the hydration process was carried out for 28 days to identify and quantify the hydrated solid phases formed. After the completion of hydration, accompanied by partial carbonation under atmospheric conditions, the carbonation process was investigated using a stirred micro-reactor by reacting cement powder with pure CO2(g) (PCO2 = 11 bar) and MilliQ water for different reaction times. The reaction time was varied to constrain the reaction kinetics of the carbonation process and to investigate the evolution of primary and secondary solid phases. Mineralogical analyses (X-ray Powder Diffraction and Scanning Electron Microscope) were carried out to this purpose. Water analyses were also performed by ion chromatography at the end of each experimental run to investigate the chemical effects of cement carbonation on the aqueous solution. The carbonation degree was calculated from the results of Thermo-Gravimetric analysis (TGA). The main results of these experiments is the quick conversion of portlandite and Ca1.60SiO3.6?2.58H2O (C-S-H) to calcite. In fact, the carbonation degree attains 80 % after 6 hours of reaction time. Experimental outcomes will be simulated by means of the PHREEQC software package to obtain further indications on cement carbonation.

This study presents the results obtained by studying well integrity in the natural analogue for the geological storage of CO2 of Sant'Albino, Southern Tuscany, which is affected by intense CO2 degassing and where a thermal spa and a CO2 production plant are present. Reaction Path Modeling (RPM) of cement hydration and carbonation as well as Reactive Transport Modeling (RTM) of cement alteration were used to investigate the processes occurring near a hypothetical average production well with a damaged leaking zone, affecting casing and cement, assuming a defined composition of class G Portland cement. It turns out that the advective flow of CO2 from the damaged zone, first, leads to completion of cement carbonation and, second, promotes further cement alteration through considerable dissolution of carbonate minerals. These processes takes place in a relatively short time, in the order of some years. The ultimate consequence of these CO2-promoted comparatively fast chemical reactions is most likely CO2 leakage to the surface.

The energy potential of geothermal reservoirs mainly depends on thermal regime, geological structure, and petrophysical properties. However, practical issues have a main importance in the planning, such as the kind of energy utilization, the design of the geothermal doublet, or the vicinity of energy end users. The evaluation approach here described tackles and integrates the different aspects. The approach is tested in the medium-enthalpy geothermal reservoir of Guardia Lombardi (Campania, Italy). The surface area of the entire study region is about 42 km by 28 km. It is characterized by specific surface heat flow of up to 90 mW m-2 and geothermal gradients of about 58 K km-1. The geothermal target is the shallow water Apulian Platform, a fractured and possibly locally karstified carbonate layer, dissected by a number of steep faults. The complex geological structure has been interpreted from several seismic profiles and hydrocarbon exploration wells. A numerical model was set up describing the relevant regional advective and conductive heat transport processes in the reservoir. A set of borehole-temperature data was used for its calibration. As simulator we used the code SHEMAT-Suite. First, we investigate the natural flow and temperature conditions in the entire reservoir. Second, we choose several sub-models, based on temperature and flow rates as well as on social decision parameters such as vicinity to villages or natural reserve restrictions. For these sub-models we assess the rates of energy production and sustainability for various utilization scenarios. Relevant aspects, beside infrastructure and natural reserve restrictions, are: (a) borehole locations and distance between injector and producer; (b) drilling depth vs. estimated temperature; (c) influence of preexisting fracture and fault systems; (d) stimulation.

The operative agreement between the Italian Ministry of Economic Development (Directorate General for Nuclear Energy, Renewable Energy, and Energy Efficiency) and the Italian National Research Council (Department of Earth and Environment), signed in 2010, promoted a new project (VIGOR project) to evaluate the geothermal potential and the implementation of innovative use of geothermal resources in the so-called Regions of Convergence (i.e., Campania, Puglia, Calabria, and Sicilia). Within this context, a characterization of medium enthalpy geothermal resources have been carried out in the promising "Guardia dei Lombardi" area, located in the Campania region (Southern Italy, Province of Avellino). Intense subsurface hydrocarbon exploration has been carried out in the area over the last decades (particularly during the 1956-1996 period), providing large quantities of seismic and geochemical data. This exploration activity has demonstrated the presence of 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 platform was deformed to shape a buried antiformal stack (NICOLAI & GAMBINI, 2007). In the study area 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). 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 (e.g., Monte Forcuso 1 and 2 wells), and saline water along the flank of the buried anticline (e.g., Bonito 1 Dir, Ciccone 1 wells). In previous assessment mainly made by ENEL (1987; 1994), a reservoir fluid has been estimated in the area that reaches temperature of 120°C at the depth of 3000 m below ground level, associated to a heat flow of 90 mW/m2. (DELLA VEDOVA et alii, 2001). These parameters suggest the presence of a medium enthalpy geothermal resource. The presence of thermal waters in the area (Terme di San Teodoro) provides further constrain about the geochemical characteristics of the reservoir water.. Reservoir fluid temperature up to about 124°C were calculated using different geothermometers (DUCHI et alii, 1995). In this study, the overall structural-stratigraphic setting of the reservoir/caprock system has been defined on the basis of the integrated interpretation of a composite dataset of surface and subsurface geological, geophysical and geochemical information. In particular, thanks to the cooperation of ENI Company, we have had access to a wide dataset composed by seismic reflection profiles, well data, logs and cores. A careful assessment of temperature field at depth has been carried out analyzing the well logs through Horner plot construction (RIDER, 1996 and reference therein). Where the data were scarce, the approach proposed by DELLA VEDOVA, et alii (2001) has been applied. 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