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• A wellbore cement sheath damage model with the integration of acoustic measurements is proposed. Wellbore cement quality analysis can be refined with the joint interpretation of both sonic and ultrasonic bond logs. • A microannulus might propagate due to thermo-mechanical stresses throughout well lifecycle soon after cement curing. • High thermal stresses, due to drastic temperature changes throughout well lifecycle, induce cement sheath failure. • A fluid-filled microannulus might propagate due to thermo-mechanical stresses at various well operations soon after cement curing. This paper presents an analytical method of predicting cement sheath integrity with incorporation of wire-line acoustic measurements on an example of a deep, high-temperature geothermal well, located in central part of the Los Humeros Geothermal Field in the northern part of the Mexican Volcanic Belt. The developed method, accounting for mechanical properties of a coupled casing-cement-rock system with the influence of temperature changes, applied internal pressures, and isotropic far-field stresses, can be easily, without additional costs and in a non-destructive way, used to evaluate cement sheath integrity during various stages of a geothermal well life cycle and help to optimize and design drilling, production, and maintenance operations. [ABSTRACT FROM AUTHOR]

The electrochemical atomic layer deposition (E-ALD) growth of chalcogenides materials enables the deposition of technologically interesting ultra-thin films. However, this method raises some questions about the actual growth mechanism. We addressed one of the more interesting anomalies reported lately: the occurrence of the Zn-deficiency and of the polycrystalline thread-like overgrown structures in the E-ALD growth of Cu x Zn y S. The present study was developed using a computational speciation approach under the mass balance method. Exploiting a well-established computational approach, but uncommonly applied to the electrochemical science, we calculated the predominance charts and the equilibrium speciation of the solid phases during the electrochemical process. On this basis, we obtained a deep insight into the mechanism underlying the E-ALD process from a thermodynamic standpoint. Thus, we identified the crucial steps of the Cu x Zn y S growth leading to the anomalies object of this research. [ABSTRACT FROM AUTHOR]

This study presents the results obtained by studying well integrity in the natural analogue for the geological storage of CO 2 of Sant’Albino, Southern Tuscany, which is affected by intense CO 2 degassing and where a thermal spa and a CO 2 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 CO 2 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 CO 2 -promoted comparatively fast chemical reactions is most likely CO 2 leakage to the surface. [ABSTRACT FROM AUTHOR]

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

Abstract: Geological storage is presently one of the most promising options for reducing anthropogenic emissions of CO2. Among the several projects investigating the fate of CO2 stored at depth, the EnCana''s CO2 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 CO2 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 m3 of supercritical CO2 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-CO2 injection water samples) provided by the International Energy Agency Weyburn CO2 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 CO2 fugacity. The oil–gas–water interaction and the non-ideality of the gas phase (with exception of CO2) 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 (CO2 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 CO2 can safely be stored by solubility (as CO2(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 CO2 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. [Copyright &y& Elsevier]

Abstract: The composition of non-methane volatile organic compounds (hereafter VOCs) in i) the cover soil, at depths of 30, 50 and 70 cm, and ii) gas recovery wells from Case Passerini landfill site, (Florence, Italy) was determined by GC-MS. The study, based on the analysis of interstitial gases sampled along vertical profiles within the cover soil, was aimed to investigate the VOC behaviour as biogas transits from a reducing to a relatively more oxidizing environment. A total of 48 and 63 different VOCs were identified in the soil and well gases, respectively. Aromatics represent the dominant group (71.5% of total VOC) in soil gases, followed by alkanes (6.8%), ketones (5.7%), organic acids (5.2%), aldehydes (3.0%), esters (2.6%), halogenated compounds (2.1%) and terpenes (1.3%). Cyclics, heterocyclics, S-bearing compounds and phenols are ≤1%. In the wells the VOC composition is characterized by higher concentrations of cyclic (7.6%) and S-bearing compounds (2%) and lower concentrations of O-bearing compounds. The vertical distribution of VOCs in the cover soil shows significant variations: alkanes, aromatics and cyclics decrease at decreasing depth, whereas an inverse trend is displayed by the O-bearing species. Total VOC and CH4 concentrations at a depth of 30 cm in the soil are comparable, inferring that microbial activity is likely affecting VOCs at a very minor extent with respect to CH4. According to these considerations, to assess the biogas emission impact, usually carried out on the sole basis of CO2 and CH4 emission rates, the physical–chemical behaviour of VOCs in the cover soil, regulating the discharge of these highly contaminant compounds in ambient air, has to be taken into account. The soil vertical distribution of these species can be used to better evaluate the efficiency of oxidative capability of intermediate and final covers. [Copyright &y& Elsevier]

Abstract: The determination of reduced S species in natural waters is particularly difficult due to their high instability and chemical and physical interferences in the current analytical methods. In this paper a new, rapid and reliable analytical procedure is presented, named the Cd–IC method, for their determination as ΣS2− via oxidation to after chemical trapping with an ammonia–cadmium solution that allows precipitation of all the reduced S species as CdS. The S2−–SO4 is analysed by ion-chromatography. The main advantages of this method are: low cost, high stability of CdS precipitate, absence of interferences, low detection limit (0.01mg/L as SO4 for 10mL of water) and low analytical error (about 5%). The proposed method has been applied to more than 100 water samples from different natural systems (water discharges and cold wells from volcanic and geothermal areas, crater lakes) in central-southern Italy. [Copyright &y& Elsevier]

Considering the range of P CO2 of previous laboratory experimental works, in this study the carbonation rate of class G Portland cement was investigated at room temperature, in the P CO2 interval from 1 to 51 bar, to fill the existing gap of knowledge, through three types of laboratory experiments. Cement hydration (accompanied by limited carbonation) was carried out for 28 days at atmospheric conditions. Cement carbonation was then investigated using a micro-reactor by reacting, in distinct runs, cement powder samples, under stirred conditions, and massive samples, under stagnant conditions, with pure CO 2 (g) and MilliQ water. After the completion of each experiment, chemical analyses on both the aqueous solution (IC, ICP-OES, acidimetric titration) and the solids (XRD, SEM, TGA/DTA) were performed. In type 1 experiments, cement powder was reacted at 11 bar P CO2 , for 1, 3, 6, 21, 67, 97 and 120 h. Portlandite was only present in the hydrated cement paste and was converted to CaCO 3 in less than 1 h. In type 2 experiments, cement powder was reacted for 6 h at P CO2 of 1, 11, 31 and 51 bar. The extent of cement carbonation was similar for any P CO2 values. The experiments of type 3 were performed with cement cube samples at 11 bar P CO2 for 6, 24 and 210 h. The average carbonation depth attained was 0.23 mm in 1 day, and resulted to be linearly related to the square root of reaction time indicating that cement carbonation rate was controlled by diffusion (Fickian behavior). [ABSTRACT FROM AUTHOR]

Abstract: Injection of spent (cooled) thermal fluids began in the Tianjin geothermal district, north-eastern China, at the end of the 1990s. Well injectivities declined after 3–4 years because of self-sealing processes that reduced reservoir permeability. The study focuses on the factors that may have caused the observed decrease in permeability, using chemical and isotopic data on fluids (water and gas) and mineral phases collected from production and injection wells. The results of data processing and interpretation indicate that (1) it is very unlikely that calcite and silica precipitation is taking place in the reservoir; (2) the Fe- and Zn-rich mineral phases (e.g. sulfides, hydroxides and silicates) show positive saturation indexes; (3) SEM and XRD analyses of filtered material reveal that the latter mineral phases are common; (4) visual observation of casings and surface installations, and of corrosion products, suggests that a poor quality steel was used in their manufacture; (5) significant quantities of solids (e.g. quartz and feldspar crystals) are carried by the geothermal fluid; (6) seasonal changes in fluid composition lead to a reduction in casing corrosion during the summer. It was concluded that the decrease in injectivity in the Tianjin wells is caused only in part by the oxidation of casings, downhole pumps, and surface installations, triggered by free oxygen in the injected fluids; the utilization of better quality steels should drastically reduce this type of corrosion. Self-sealing of pores and fractures by reservoir formation solids and by the Fe-corrosion products suspended in the injected fluids seems to be a more important phenomenon, whose effect could be greatly reduced by installing filtering devices at all sites. [Copyright &y& Elsevier]

Electrochemical Atomic Layer Deposition (E-ALD), exploiting surface limited electrodeposition of atomic layers, can easily grow highly ordered ultra-thin films and 2D structures. Among other compounds Cu x Zn y S grown by means of E-ALD on Ag(111) has been found particularly suitable for the solar energy conversion due to its band gap (1.61 eV). However its growth seems to be characterized by a micrometric thread-like structure, probably overgrowing a smooth ultra-thin films. On this ground, a SXRD investigation has been performed, to address the open questions about the structure and the growth of Cu x Zn y S by means of E-ALD. The experiment shows a pseudo single crystal pattern as well as a powder pattern, confirming that part of the sample grows epitaxially on the Ag(111) substrate. The growth of the film was monitored by following the evolution of the Bragg peaks and Debye rings during the E-ALD steps. Breadth and profile analysis of the Bragg peaks lead to a qualitative interpretation of the growth mechanism. This study confirms that Zn lead to the growth of a strained Cu 2 S-like structure, while the growth of the thread-like structure is probably driven by the release of the stress from the epitaxial phase. [ABSTRACT FROM AUTHOR]

Estimating values of permeability (k), efficient porosity (P) and hydraulic conductivity (K) by analysing field outcrops as analogue of geothermal reservoirs, is a timely theme useful for predictions during geothermal exploration programs. In this paper we present a methodology providing k, P and K values, based on geometric analysis of quartz-tourmaline faults-vein arrays hosted in micaschist exposed in south-eastern Elba Island (Tuscan Archipelago, Italy), considered as the analogue of rock hosting the so-called “deep reservoir” in the Larderello geothermal field. The methodology is based on the integration among structural geology, fluid inclusions results and numerical analyses. Through a detailed structural mapping, scan lines and scan boxes analyses, we have reconstructed three superposed faulting events, developed in an extensional setting and framed in the Neogene evolution of inner Northern Apennines. Geometrical data of the fault-veins array were processed by reviewing the basic parallel-plate model equation for k evaluation. Fluid inclusion analyses provided those salinity and pressure-temperature values necessary for defining density and viscosity of the parent geothermal fluids. Then, permeability, density and viscosity were joined to get hydraulic conductivity (K). Permeability is estimated between 5 × 10 −13 and 5 × 10 −17 m 2 with variations among the different faults generation, while the hydraulic conductivity is encompassed between 1.31 × 10 −8 and 2.4 × 10 −13 m/s. The obtained permeability and hydraulic conductivity values are comparable with those from several geothermal areas, and in particular from the Larderello geothermal field. The main conclusion is that the proposed integrated approach provides a reliable methodology to obtain crucial values, normally obtained after drilling, for developing numerical flow models of geothermal fluid path in active geothermal systems by field and laboratory analyses of analogue, exhumed, geothermal systems. [ABSTRACT FROM AUTHOR]

A SEM, DRS and XAS study was carried out on ultra-thin films with chemical composition belonging to the Cu-Zn-S ternary system, related to the kesterite-type materials, in the light of their potential application to thin film photovoltaic technology. The films, realized through the layer-by-layer E-ALD electrochemical technique, reveal variable phase composition as a function of the applied E-ALD sequence. In particular, by increasing the Zn cycles per Cu cycle from 1:1 to 9:1, the number of detected phases changes from 3 to 2. In all samples, Cu mainly crystallize in a Cu 2 S type phase, whereas Zn occurs as ZnS. In the 1:1 sample, additional ZnO is detected. The variable phase composition parallels apparent changes in the sample morphology. In all samples, a sulphide thin film is covered by a net of elongated nanostructures, the length of which decreases with increasing the number of Zn cycles per Cu cycle. All these evidences are interpreted as due to the operating electrochemical route during the synthesis and confirm the lack of miscibility between Cu 2 S and ZnS, thermodynamically relevant after the E-ALD has stopped. The band gap values exhibited by the three films, modulated by changing the copper:zinc ratio, progressively approach a value useful for solar energy conversion, thus strongly proposing these new sulfide nanomaterials for photovoltaics and photochemical applications. [ABSTRACT FROM AUTHOR]

Deactivation is one the main causes still preventing the full exploitation of palladium electrocatalysts in alkaline direct alcohol fuel cells and the electrochemical reforming of alcohols. While often attributed to the adsorption of poisoning species generated in the alcohols oxidation, in the present work we demonstrate that deactivation is provoked by the formation of palladium oxides. A combined approach including i) fuel cell runs, ii) cyclic voltammetry and iii) near edge X-ray absorption spectroscopy has enabled us to draw the conclusions reported in the paper. [ABSTRACT FROM AUTHOR]

Abstract: A geochemical survey of thermal waters collected from submarine vents at Panarea Island (Aeolian Islands, southern Italy) was carried out from December 2002 to March 2007, in order to investigate (i) the geochemical processes controlling the chemical composition of the hydrothermal fluids and (ii) the possible relations between the chemical features of the hydrothermal reservoir and the activity of the magmatic system. Compositional data of the thermal water samples were integrated in a hydrological conceptual model, which describes the formation of the vent fluid by mixing of seawater, seawater concentrated by boiling, and a deep, highly-saline end-member, whose composition is regulated by water-rock interactions at relatively high temperature and shows clear clues of magmatic-related inputs. The chemical composition of concentrated seawater was assumed to be represented by that of the water sample having the highest Mg content. The composition of the deep end-member was instead calculated by extrapolation assuming a zero-Mg end-member. The Na–K–Ca geothermometer, when applied to the thermal end-member composition, indicated an equilibrium temperature of approximately 300°C, a temperature in agreement with the results obtained by gas-geothermometry. [Copyright &y& Elsevier]

• A complex mineralogical assemblage was revealed. • Fe(II) and Fe(III) species were detected in a variety of coordination environments. • The Fe oxidation state and speciation is not affected by water. • Significant changes were evidenced as a function of particle granulometry. • Ashes surface features may prevent direct exposure to mobile and toxic Fe(II). Volcanic ashes particles are subjected to substantial modification during explosive eruptions. The mineralogical and compositional changes have important consequences on the environment and human health. Nevertheless, the relationship between the speciation of iron (Fe) and the mineralogical composition and particle granulometry of the ashes, along with their interaction with water, are largely unknown. In particular, the Fe oxidation state and the possible formation of new Fe-bearing phases in presence of S, Cl, and F in the plume are key points to assess the impact of the ashes. Fragmental material ejected during volcanic activity (tephra) in 2013, was collected on the Mt. Etna (Italy) and investigated using a multi-technique approach that included conventional Electron Paramagnetic Resonance (EPR), high field EPR (HFEPR), EchoEPR, and Fe K-edge X-ray Absorption Spectroscopy (XAS). These element-selective techniques allowed obtaining a detailed information on the oxidation state and coordination environment of Fe, and of its speciation in the ash samples as a function of the granulometry. A complex mineralogical assemblage, consisting of variable amounts of nanometric crystalline Fe inclusions in a glass matrix, and of Fe-oxides and Fe-sulfur phases was revealed. A risk assessment of the ashes is attempted. [ABSTRACT FROM AUTHOR]

In the present study the stability of the phases pertaining to the Cu–Fe–S–O–H compositional system is investigated using the Eh-pH prevalence diagrams. Calculations were performed under the PHREEQC formalism, simultaneously accounting for all concurrent equilibria. Accordingly, point-to-point mass balance diagrams were realised, changing initial parameters to explore the dependence of the system on the temperature, and on the metal-to-sulfur ratio. Among the most relevant results, discussed in comparison with the previous existing literature mainly driven by calculation performed under the so-called line method approximation, the occurrence of large field of stability of the ternary species (and, among them, of delafossite, CuFeO 2) and the net change of some boundaries in the stability fields of the binary species, due to competing equilibria. The results have been discussed on the light of the occurrence of these minerals in cuprous and ferrous mineralizations, and in the perspective of possible application in Corrosion Science. • New thermodynamic modelling in the Cu–Fe–S–O–H system. • Eh-pH at temperature higher than room temperature. • Revised predominance field for ternary phases in the Cu–Fe–S–O–H. • Cu–Fe–S–O–H is not just the sum of Cu–S–O–H and Fe–S–O–H. [ABSTRACT FROM AUTHOR]