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The Nirano mud volcano is located in the western sector of the Modena Apennine margin (Italy). It represents one of the most spectacular phenomena of sedimentary volcanism in the entire Italian territory and is among the largest in Europe. Here numerous aligned gryphon clusters and seeping pools constantly burst gas and mud inside a morphological depression. Besides the obvious surface expressions of these emission spots, until now the type and amount of gas released in the rest of the large Nirano caldera zone remained unknown. An extensive geochemical soil gas survey (O2, N2, CO2, CH4, 222Rn, He, H2, and light hydrocarbons) and exhalation fluxes (CO2 and CH4), was carried out inside the mud volcano field with the aim of identifying soil degassing distribution, and to estimate the micro- and macro-seepage budget for both CO2 and CH4. Soil gas data highlight the presence of two zones characterized by high concentrations and flux values. These enhanced seepage zones are located in the SW and NE sectors of the mud volcano suggesting that the enhanced gas emissions present in the peripheral zones, are controlled by caldera collapse structures. The most significant CO2 flux (up to 91 g m−2 d−1) and 222Rn anomalies are located in the central part of the crater in correspondence of a morphological escarpment. Here we infer the presence of a buried tectonic system of collapsed terraces that facilitate fluids degassing. In contrast, CH4 fluxes show a scattered distribution and low values (mean 221 mg m−2 d−1). Overall the CH4 degassing budget is low (27.09 t km−2 y−1) when compared with other Italian mud volcanoes. This could be related to a relative low emission activity during the period of the geochemical survey and to a more homogeneous dilution of surface distribution of the emission point-s. Chemical and isotopical composition of the gas discharged from the active gryphons is methane-dominated and the thermogenic signature (ranging from −41 to −47‰) suggests a deep reservoir source. This conclusion is supported by noble-gas measurements (He, Ne, Ar, Kr, Xe) conducted in the pore water phase of the emitted mud, indicating a secondary gas exchange occurring at a depth of a few kilometers. The geochemical anomalies found in this study, successfully predicted the occurrence of new degassing phenomena towards the NE sector of the caldera. Indeed recently (i.e. after the survey data acquisition) new manifestations of mud and gas emissions appeared in the north-eastern edge of the caldera.

Several soil gas surveys were performed from 2008 to 2015 in Medolla (Northern Italy) within a farming area characterized by macroseeps, absence of vegetation and anomalous temperatures of soil to investigate the soil gas migration mechanism and verify the presence of a buried fault intersecting the macroseeps. In this work, we show results of soil gas measurements of radon and thoron activities, and helium and carbon dioxide concentrations, which have been carried out in the area struck of the 2012 seismic sequence.We found that the seismic sequence sensibly influenced the soil gas distribution in the area. Indeed, soil gas anomalies are useful to recognize influences of surface features on natural gas migration. The study of the association of different gases with different origin and physical/chemical behaviour, the collection of a large number of samples during the dry season and the use of proper data analysis are fundamental in the comprehension of gas migration mechanism. The study of spatial distribution of soil gas anomalies can give information on the origin and processes involving deep and superficial gas species. In particular, the study of the spatial distribution of radon, often together with other soil gases, appears to be a suitable tool for identifying active tectonic structures in faulted areas.222Rn and 220Rn were recorded starting from 2012, early after the mainshock of 20th May. The May 2012 distribution map shows a broad sector of the area with anomalous values approximately aligned NW-SE. Radon vs thoron distribution data highlighted two different circulation mechanisms. After an initial perturbation of the system in May, a deep fluid migration is prevalent in September 2012. From 2013, the soil degassing returned to the main shallow origin. Over time, the anomalous high values of all the investigated species were always measured in correspondence of macroseeps supporting the hypothesis of a hidden fault. However, 222Rn values collected early after the mainshocks have ubiquitous distribution, likely due to perturbation of the system which enhanced the degassing of surficial layers and masked the deep contribution. The shallow and deep contributions presumably coexist for the other data, located at the intersection of the two trends. Over time 222Rn is better related to CO2 concentrations than CH4, in particular for the May 2012, 2013 and 2015 surveys (0.43 < r > 0.60) and, to a lesser degree, for Sept 2012 (r = 0.25). This relationship suggests that CO2 likely acts as a carrier for 222Rn allowing it to quickly reach the surface. Although, generally, radon concentrations increase with flow, elevated mass flux due to high flows can dilute the 222Rn activities and its values recorded at the surface. This phenomenon could justify the slightly anomalous values in correspondence of macroseeps.Geochemical surveys highlight the importance to carry out a discrete monitoring that can help to study the stress/strain changes related to seismic activity that may force crustal fluid to migrate up, thereby altering the geochemical characteristics of the fault zone at surface before and after earthquakes.

Soil gas and Electrical Resistivity Tomography (ERT) surveys were performed in Medolla (Emilia-Romagna Region, northern Italy) within a farming area characterized by macroseeps, absence of vegetation and anomalous temperatures of soil to investigate the soil gas migration mechanism and verify the presence of a buried fault intersecting the macroseeps. Soil gas (222Rn, 220Rn, He and C2H6) concentrations and flux (φCO2 and φCH4) measurements were carried out from 2008 to 2015, comprising the 2012 Emilia seismic sequence. Moreover, in 2016 a ERT survey, combined with new flux measurements, was performed along four profiles (ranging from 180 to 630 m long) centered on the main macroseep. We found that the seismic sequence sensibly influenced the soil gas distribution in the area. All investigated species, but He, increased their values early after the mainshocks, likely due to crustal deformation which promoted the geogas uprising. In 2015, when the stress has vanished, these concentrations gradually decreased toward pre-seismic values. Helium concentrations showed an opposite behavior as they decreased in May 2012 and then gradually increased over time. This trend may be reasonably due to the enhancement of the strain field which promoted the He dissipation from soil to the atmosphere, due to its high volatility. In all the geochemical surveys conducted from 2008 to 2015, soil gas high values around the main macroseeps were identified, delighting the presence of an alignment in the E-W direction. This trend, identified for several gas species, ultimately supports the theory of a hidden fault which favors the intensification of fluids migration along zones characterized by greater permeability. ERT results highlighted a sub-horizontal layering characterized by different resistivity intervals, roughly matching local stratigraphy. In most profiles we observed a slightly increase of resistivity and a sharp interruption of the electro-layering in correspondence of the main macroseep, both near the surface and at depth. This implies that a fracture zone due to the presence of a buried fault cannot be excluded. The combined use of geochemical and geophysical techniques in this study confirmed the usefulness of such multiparametric approach for mapping out hidden structures in tectonically active areas, allowing to better understanding the fluid migration processes through preferential leakage pathways.

The worldwide increasing energy demand triggered studies focused on defining the underground energy potential even in areas previously discharged or neglected. Nowadays, geological gas storage (CO2 and/or CH4) and geothermal energy are considered strategic for low-carbon energy development. A widespread and safe application of these technologies needs an accurate characterization of the underground, in terms of geology, hydrogeology, geochemistry and geomechanics. However, during pre-feasibility study-stage, the limited number of available direct measurements of reservoirs, and the high costs of reopening closed deep wells must be taken into account. The aim of this work is try to overcome these limits, proposing a new methodology to reconstruct vertical profiles, from surface to reservoir base, of: i) thermal capacity, ii) thermal conductivity, iii) porosity and iv) permeability, through integration of well-log information, petrographic observations on inland outcropping samples and, flow and heat transport modelling. As case study to test our procedure we selected a deep-structure, located in the medium Tyrrhenian Sea (Italy). Obtained results are consistent with measured data, confirming the validity of the proposed model. Notwithstanding intrinsic limitations due to manual calibration of the model with measured data, this methodology represents a useful tool for reservoir and geochemical modellers that need to define petrophysical input data for underground modelling before the well reopening. This article is protected by copyright. All rights reserved.

CO2 injection in saline aquifers is one solution to avoid the emission of this greenhouse gas to the atmosphere. This process induces a pore-pressure build-up around the borehole that generates tensile and shear micro-earthquakes which emit P and S waves if given pressure thresholds are exceeded. Here, we develop a simple model to simulate micro-seismicity in a layer saturated with brine, based on an analytical solution of pressure diffusion and an emission criterion for P and S waves. The model is based on poroelasticity and allows us to obtain estimations of the hydraulic diffusivity on the basis of the location of the micro-earthquakes (defining the CO2 plume) and the triggering time. Wave propagation of P and S waves is simulated with a full-wave solver, where each emission point is a source proportional to the difference of the pore pressure and the tensile and shear pressure thresholds. Finally a reverse-time migration algorithm is outlined to locate the asynchronous sources induced by the fluid flow, determinated by the maximum amplitude at each cell versus the back propagation time.

Soil surveys were performed in Medolla (Italy), a peculiar area characterized by spotty high soil temperature, gas vent, and lack of vegetation, to determine the migration mechanisms and spatial behavior of gas species. Hereby we present soil gas measurements and their isotopic ratios measured between 2008 and 2015, including the 2012 Emilia-Romagna seismic sequence. We found that soil gas concentrations markedly changed during the main shocks of May 20 and 29, 2012 (Mw 6.1 and 6.0, respectively), highlighting the presence of a buried fault intersecting the gas vents. We suggest that crustal dilation associated with seismic activity favored the uprising of geogas towards the surface. Changes in the isotopic signature highlight the contribution of two distinct sources, one deeper, thermogenic and another superficial related to organic-rich layer, whose relative contribution varied before, during and after the earthquake. We suppose an increase of microbial component likely due to the ground shaking of shallower layers linked to seismic sequence, which masks the thermogenic contribution. Although the changes we detect are specific for an alluvial plain, we deduce that analogous processes may be active elsewhere, and that soil gas geochemistry represents an useful tool to discriminate the gas migration related to seismic activity.

$$\hbox {CO}_{2}$$ sequestration in geological formations requires specific conditions to safely store this greenhouse gas underground. Different geological reservoirs can be used for this purpose, although saline aquifers are one of the most promising targets due to both their worldwide availability and storing capacity. Nevertheless, geochemical processes and fluid flow properties are to be assessed pre-, during, and post-injection of $$\hbox {CO}_{2}$$ . Theoretical calculations carried out by numerical geochemical modeling play an important role to understand the fate of $$\hbox {CO}_{2}$$ and to investigate short-to-long-term consequences of $$\hbox {CO}_{2}$$ storage into deep saline reservoirs. In this paper, the injection of $$\hbox {CO}_{2}$$ in a deep structure located offshore in the Tyrrhenian Sea (central Italy) was simulated. The results of a methodological approach for evaluating the impact that $$\hbox {CO}_{2}$$ has in a saline aquifer hosted in Mesozoic limestone formations were discussed. Seismic reflection data were used to develop a reliable 3D geological model, while 3D simulations of reactive transport were performed via the TOUGHREACT code. The simulation model covered an area of $$>$$ 100 km $$^{2}$$ and a vertical cross-section of $$>$$ 3 km, including the trapping structure. Two simulations, at different scales, were carried out to depict the local complex geological system and to assess: (i) the geochemical evolution at the reservoir–caprock interface over a short time interval, (ii) the permeability variations close to the $$\hbox {CO}_{2}$$ plume front, and (iii) the $$\hbox {CO}_{2}$$ path from the injection well throughout the geological structure. One of the most important results achieved in this study was the formation of a geochemical barrier as $$\hbox {CO}_{2}$$ -rich acidic waters flowed into the limestone reservoir. As a consequence, a complex precipitation/dissolution zone formed, which likely plays a significant role in the sequestration of $$\hbox {CO}_{2}$$ due to either the reduction of the available storage volume and/or the enhancement of the required injection pressure.

A potential CO2 storage site located offshore the west coast of Italy, has been modelled using PFLOTRAN assuming an injection rate of 1.5 Mtons/year for 20 years. The model predicts a CO2 footprint characterised by a diameter of about 3.5 km and a maximum pressure build up of 38 bars. The solubility trapping has been quantified, predicting a dissolution in brine of 69% and 79% of the total amount of CO2 injected after 1000 and 2000 years respectively. The residual trapping has also been found to play an important role, with 9% and 6% of the injected CO2 being locked into the hosting matrix pores after 1000 and 2000 years respectively. Considering a worst-case scenario for leakages, where zero critical capillarity pressure has been assumed, minor CO2 leakages through the caprock have been identified, caused by the combined effects of the long-term structural trapping and the large and lasting overpressure caused by the CO2 injection in an ideally closed system. Finally, some preliminary work undertaken as part of an ongoing effort to couple a geochemical model to the multi-phase flow simulations reveals i) small changes in mineral volume fraction and porosity during and after the injection (~5% after 1000 years), and ii) a not negligible self-sealing effect due to precipitation of calcite in the lower layer of the caprock. Further investigations and longer physical time runs are needed to confirm this assumption, but also to gain more confidence on the geochemical model built so far and to estimate the mineral trapping potential for this site. © 2013 The Authors. Published by Elsevier Ltd. Selection and peer-review under responsibility of SINTEF Energi AS.

In recent decades, the worldwide demand for energy has been increasing, with an associated rise in CO2 emissions being observed. In such conditions, the development of “low carbon energy technologies” and strategic energy-mix plans is necessary, and an evaluation of the underground energy potential may be a useful step in developing these plans. This evaluation involves the synergic development of such technologies as: coal combustion in combination with CO2 geological storage (CCS), natural gas geological storage (CH4-GS) and geothermal energy (GE), especially in densely populated countries, such as Italy. Currently, 13.7% of Italian energy demand is met by foreign providers. Most of the Italian regions have energy deficits, and the Latium Region (in Central Italy) represents one of those in the worst conditions. This work proposes a methodology to develop energy-mix scenarios, starting in Latium, to identify areas that are potentially suitable for CCS, CH4-GS and GE. Six geothermal systems and one CO2/CH4 storage potential area were identified. Three main scenarios are proposed: (A) a combination of CH4-GS with methane as cushion gas and GE; (B) a combination of CH4-GS with CO2 as cushion gas and GE; (C) a combination of CCS and GE. Scenario A results in a reduction of the regional energy deficit that ranges from 21.8% to 45.6%. In Scenario B, the regional energy deficit reduction ranges from 30.8% to 80.7% and the CO2 emissions reduction ranges from 1.4% to 5.6%, supposing an injection of 20 years. Scenario C shows a decrease in the regional energy deficit that ranges from 15.9% to 22.1%, while the CO2 emissions reduction ranges from 7.1% to 31.3%, over the same time period. The proposed scenarios may be useful not only for the scientific community but also for policymakers as they identify the most reliable energetic strategies. Thus, this case study could be extended to the entire Italian territory with the ultimate goal of reaching energy autonomy in each region.

The estimation of CO2 storage capacity in deep geologic formations is a pre-requisite for an efficient and safe application of Carbon Capture and Storage (CCS). The evaluation of storage resources for CO2 geological sequestration is a challenging task and has been tackled using several static algorithms and dynamic methods, on a variety of scales ranging from country to site-specific. The purpose of this study is to present an up-to-date as well as an overall review of the storage capacity algorithms for oil and gas reservoirs, coal seams, and deep saline aquifers, including some worldwide estimation examples. Moreover, a practical application at local scale was also performed for an Italian deep reservoir located in the Po Plain (Northern Italy). The effective storage capacities were obtained applying the commonly established static methods, using both the theoretical and the geocellular volume of the reservoir. Although a conservative approach, this study demonstrates that the selected structure has favorable characteristics for CO2 geological storage and has the capacity to host the most part of the Po Plain CO2 emissions for several decades.

One of the most promising options to stabilize and reduce the atmospheric concentration of greenhouse gases is Carbon Capture and Storage (CCS). This technique consists of separating CO2 from other industrial flue gases and storing it in geological reservoirs, such as deep saline aquifers, depleted oil and/or gas fields, and unminable coal beds. A detailed reworking of all available Italian deep-drilling data was performed to identify potential storage reservoirs in deep saline aquifers. Data were organized into a GIS geo-database containing stratigraphic and fluid chemistry information as well as physiochemical characteristics of the geological formations. Caprock efficiency was evaluated via numerical parameterization of rock permeabilities, defining the “Caprock Quality Factor” (Fbp) for each well. The geo-database also includes strategic information such as the distribution of deep aquifers, seismogenic sources and areas, seismic events, Diffuse Degassing Structures, heat flow, thermal anomalies, and anthropogenic CO2 sources. Results allow the definition of potentially suitable areas for future studies on CO2 geological storage located in the fore-deep domains of the Alps and Apennines chains, where efficient marly-to-clayish caprocks lie above deep aquifers hosted in sands or limestones. Most of them are far form seismogenic sources and Diffuse Degassing Structures.

Geological storage is presently one of the most promising options for reducing anthropogenic emissions of CO 2 . Among the several projects investigating the fate of CO 2 stored at depth, the EnCana's CO 2 injection EOR ( Enhancing Oil Recovery ) project at Weyburn (Saskatchewan, Canada) is the most important oil production development that hosts an international monitoring project. In the Weyburn EOR Project CO 2 is used to increase recovery of heavy oil from the Midale Beds, a Mississippian reservoir consisting of shallow marine carbonate, where about 3 billions standard m 3 of supercritical CO 2 have been injected since 2000 with an injection rate of 5000 ton/day. In this work the available dataset (bulk mineralogy of the reservoir, gas-cap composition and selected pre- and post-CO 2 injection water samples) provided by the International Energy Agency Weyburn CO 2 Monitoring & Storage Project has been used in order to: i) reconstruct the pre-injection reservoir chemical composition (including pH and the boundary conditions at 62 °C and 15 MPa); ii) assess the evolution of the reservoir subjected to CO2 injection and predict dissolution/precipitation processes of the Weyburn brines over 100 years after injection; iii) validate the short-term (September 2000–2003) evolution of the in situ reservoir fluids due to the CO2 injection, by comparing the surface analytical data with the composition of the computed depressurized brines. To achieve these goals the PRHEEQC (V2.14) Software Package was used with both modified thermodynamic database and correction for supercritical CO 2 fugacity. The oil–gas–water interaction and the non-ideality of the gas phase (with exception of CO 2 ) were not considered in the numerical simulations. Despite intrinsic limitations and uncertainties of geochemical modeling, the main results can be summarized, as follows: 1) the calculated pre-injection chemical composition of the Midale Beds brine is consistent with the analytical data of the waters collected in 2000 (baseline survey), 2) the main reservoir reactions (CO 2 and carbonate dissolution) take place within the first year of simulation, 3) the temporal evolution of the chemical features of the fluids in the Weyburn reservoir suggests that CO 2 can safely be stored by solubility (as CO 2(aq) ) and mineral trapping (via dawsonite precipitation). The short-term validation performed by calculating chemical composition of the reservoir fluids (corrected for surface conditions) after the simulation of 3 years of CO 2 injection is consistent (error ≤ 5%) with the analytical data of the wellhead water samples collected in 2003, with the exception of Ca and Mg (error > 90%), likely due to complexation effect of carboxilic acid.

Periodico semestrale del Servizio Geologico d'Italia - ISPRA e della Societa Geologica Italiana

Geochemical and geophysical surveys were carried out in the Cagno valley (Sila massif, central-northern Calabria, Italy) to investigate the gas bearing properties of a seismogenic fault (Lakes Fault, LF), discovered by paleoseismological analysis. Soil gas measurements (N2, O2, Rn, CO2, CH4 and light hydrocarbons) and exposure to γ radiations were performed along two detailed profiles (about 150 m long), trending almost parallel to a trench crossing the LF. The highest values of Rn, γ radiation, CO2, CH4 and light hydrocarbons were detected in the area around the LF and 100 m far away. In the central part of the profiles, where a hanging valley is present, geo-gas distribution is likely controlled by both lithology (colluvial deposits and peaty silt deposits, characterized by medium to low permeability) and the presence of a local cold aquifer. In particular, water table influences the circulation of the gas species in the sub-surface environment, as well as their distribution at the surface by playing a sort of sealing effect for the gas migration. In the area located about 100 m westward of the fault, characterized by soils originated from altered granodiorites, the occurrence of a previously unknown blind fault is supposed. The multidisciplinary approach of this work allows to better understand the relationship between geochemical and geophysical analyses linked to migration processes of deep fluid through preferential leakage pathways providing some hints on the spatial influence of active tectonic.

On May 20th and 29th, 2012 two earthquakes (ML 5.9 with hypocenter depth at 6.3 km and ML 5.8 with hypocenter depth at 10.2 km, respectively; ISIDe Database 2010) struck the Emilia area. The epicentre was located in the vicinity of Finale Emilia and Medolla (Modena). Co-seismic effects exemplified by liquefactions and surface ruptures occurred in the surrounding area (Provinces of Bologna, Ferrara, Modena, Reggio Emilia, Mantova and Rovigo). The maximum effects where concentrated along the towns located 15–25 km from the epicentre (SW portion of Ferrara Province). Soon after the main events, several geochemical and geophysical surveys were carried out in different sites at Modena and Ferrara Provinces, where surface rupture and liquefaction effects were most evident. Results gained from soil and dissolved gases and geoelectrical-geophysical surveys evidenced that the main liquefied layer is related to a medium coarse-grained sand saturated aquifer located at 8–12 m b.g.l. On the other hand, superficial unsaturated sediments underwent liquefaction represented by densification and lateral spreading. As a consequence, liquefied soil caused ground failures and damages to the built environment. The extent of the liquefaction phenomena, its concentration along the Reno paleo-river ridge and the building damage, has highlighted the need to further characterized the possible rule of lithology and natural gas content on the outset of liquefaction.

The epicentral area of the Emilia seismic sequence is located in the Emilia-Romagna Region (northern Italy), 45 km from the city of Modena (Figure 1). This area is sited within thrust-related folds of the Ferrara Arc, which represent the most external part of the northern Apennines. This sector is considered as having been active during late Pliocene to early Pleistocene times [Scrocca et al. 2007] and encompasses also the Mirandola and Ferrara seismogenic sources [e.g., Burrato et al. 2003, Boccaletti et al. 2004, Basili et al. 2008]. The main sedimentary infilling of the Po Plain is represented by Pliocene–Pleistocene alluvial deposits (alternating fluvial sands and clays) that overlie a foredeep clastic sequence, with a total average thickness of 2 km to 4 km [e.g., Carminati et al. 2010]. Soon after the mainshock, several liquefaction phenomena coupled to ground fractures were observed in the epicentral area (e.g., San Carlo, Ferrara). Soil liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. […] Collapsed caves reported in the literature and/or local press [e.g., Febo 1999, Martelli 2002] in the epicentral area were previously investigated by our research group in 2008, with several soil measurements of CO2 and CH4 fluxes. Immediately after the May 20, 2012, mainshock and during the Emilia seismic sequence, the collapsed caves were sampled again to determine any variations in these CO2 and CH4 fluxes. In this survey, newly formed collapsed caves were also found and measured (especially in the northern part of investigated area). […]

In densely populated countries there is a growing and compelling need to use underground for different and possibly coexisting technologies to produce “low carbon” energy. These technologies include (i) clean coal combustion merged with CO2 Capture and Storage (CCS); (ii) last-generation nuclear power or, in any case, safe nuclear wastes disposal, both “temporary” and “geological” somewhere in Europe (at least in one site): Nuclear wastes are not necessarily associated to nuclear power plants; (iii) safe natural gas (CH4) reserves to allow consumption also when the foreign pipelines are less available or not available for geopolitical reasons and (iv) “low-space-consuming” renewables in terms of Energy Density Potential in Land (EDPL measured in [GW h/ha/year]) as geothermics. When geothermics is exploited as low enthalpy technology, the heat/cool production could be associated, where possible, to increased measures of “building efficiency”, low seismic risks building reworking and low-enthalpy heat managing. This is undispensable to build up “smart cities”. In any case the underground geological knowledge is prerequisite. All these technologies have been already proposed and defined by the International Energy Agency (IEA) Road Map 2009 as priorities for worldwide security: all need to use underground in a rational and safe manner. The underground is not renewable in most of case histories [10] , [11] . IEA recently matched and compared different technologies in a unique “Clean Energy Economy” improved document (Paris, November 16–17, 2011), by the contribution of this vision too (see reference). In concert with “energy efficiency” improvement both for plants and buildings, in the frame of the “smart cities” scenarios, and the upstanding use of “energy savings”, the energetic planning on regional scale where these cities are located, are strategic for the year 2050: this planning is strongly depending by the underground availability and typology. Therefore, if both literature and European Policy are going fast to improve the concept of “smart cities” this paper stresses the concept of “smart regions”, more strategic than “smart cities”, passing throughout a discussion on the synergic and conflicting use of underground to produce energy for the “smart regions” as a whole. The paper highlights the research lines which are urgent to plan the soundest energy mix for each region by considering the underground performances case by case: a worldwide mapping, by GIS tools of this kind of information could be strategic for all the “world energy management” authorities, up to ONU, with its Intergovernmental Panel on Climate Change (IPCC), the G20, the Carbon Sequestration Leadership Forum (CSLF) and the European Platforms such as the “Zero Emissions Fossil Fuel Power Plants” (EU-ZEP Platform), the Steel Platform, the Biomass Platform too. All of these organizations agree on the need for synergistic and coexistent uses of underground for geological storage of CO2, CH4, nuclear waste and geothermic exploitation. The paper is therefore a discussion of the tools, methods and approaches to these underground affecting technologies, after a gross view of the different uses of underground to produce energy for each use, with their main critical issues (i.e. public acceptance in different cases). The paper gives some gross evaluation for the Lazio Region and some hints from the Campania Region, located in Central Italy. Energy Density Potential in Land (EDPL), is calculated for each renewable energy technology (solar, wind, geothermal) highlighting the potentiality of the last. Why the Italian case history among the densely populated countries? on the Italian territory is hard to find suitable areas (mostly if greenfields) to use the own underground, with respect to other European countries, due to the presence of seismotectonic activity and many faulted areas characterized by Diffuse Degassing Structures (DDSs, which are rich in CO2 and CH4). In this cases, public acceptance must be facilitated by the concerted efforts of researchers, universities, NGOs and policy-makers.

Italy is one of the most promising prone areas to study the CO 2 behavior underground, the caprock integrity to the CO 2 leakage, mostly in presence of pervious/geochemically active faults, due to a wide availability of CO 2 rich reservoirs at a depth between 1 and 10 km, as highlighted by recent literature. These deep CO 2 reservoirs generate at least 200 leakage areas at surface throughout Italy which have been defined “Diffuse Degassing Structures” (DDS) by INGV. These are widely studied by INGV institutionally by a long term convention with the Civil Protection Department (DPC) with the aim to catalog, monitor and assess the Natural Gas Hazard (NGH, namely the probability of an area to become a site of poisonous peri-volcanic gas exhalation from soils). More than 150 researcher of INGV are involved in monitoring areas affected by the CO 2 presence underground and at surface, by continuous monitoring on-line networks (around 40 stations throughout Italy, including the Etna area, Aeolian Islands, Umbria region, Piemonte region, etc.) and discretely (9 groups of research were involved in the last years to localize, define and monitor almost all the DDSs in Italy), by sampling and analyzing chemical and isotopic compounds, useful to discriminate the origin, evolution and natural gas hazards of the examined DDS. In this paper, we will discuss some DDS catalogued and studied by a Rome INGV Research Unit (UR 11) which focused its work in Central Italy, throughout different DDS, also in relation to the diverse seismotectonic settings, to discover buried faults as possible gas leakage pathways, mostly if they are “geochemically” activated. In particular we discuss, among the discrete monitoring techniques exploited by INGV, soil gas surveying, which consists in a collection of gas samples from the soil zone not saturated (dry zone) to measure the geogas gaseous species both in fluxes (CO 2 , CH 4 , 222 Rn) and in concentration (He, H 2 , H 2 S, helium, hydrogen, CO 2 , CH 4 , 222 Rn), that permeate the soil pores. The total CO 2 flux budget was calculated as “baseline” degassing rate of these “ CO 2 analogues”. A good discrete areal monitoring is prerequisite to design sound continuous monitoring network to monitor CO 2 related parameters in liquid/gas phases, to review the protocol of the Annex II of the European Directivity on CCS.