Surface gas measurements and related studies for the characterization and monitoring of geological CO2 storage sites; experiences at Weyburn and in Salah.

Preliminary baseline soil gas data collected in the summer and autumn of 2001 above the Phase 1A injection area of the EnCana Enhanced Oil Recovery project at the Weyburn oilfield in south Saskatchewan was presented at GHGT-6 in Kyoto. Data can now be presented for all three years of the study with conclusions, the predominant one being that the major controls on soil gas levels are seasonal and meteorological with no indications of leakage from depth. In the autumns of 2002 and 2003 further in situ monitoring of CO2, CO2 flux, O2, CH4, radon (222Rn) and thoron (220Rn) was carried out. Soil gas samples were also collected for laboratory analysis of helium, permanent gases, sulphur species and light hydrocarbons. All sampling was repeated over the same 360 point sampling grid and more detailed profiles for both follow-up years. Marked changes in CO2 levels (especially flux) for each of the three-year datasets indicate changes in surface conditions, rather than CO2 from a deeper source. The radon and thoron data was found to be similar for the three years but appears to vary in response to drift composition, and seasonal effects, rather than migration from a deep source. In 2003 further work was agreed in addition to the main grid and profile data. A control area was sampled for the same suite of gases, 10km to the northwest of the oil field. It included similar topography, land use and drift composition to the main sampling grid. There were 35 sample locations on a 7 x 5 point grid with 100m spacing and two additional sites. Early conclusions indicate that the soil gas results in the control area are very similar to those from the main grid, vindicating control site selection and further supporting a lack of deeply sourced CO2 over the injection area. Along with the control site, five zones of possible CO2 leakage were also surveyed and sampled. Two cross a river lineament that may be associated with deep faulting, two were abandoned oil well sites and one site overlays a deep salt dissolution feature. (Unfortunately CO2 flux and gamma measurements were not carried out at these sites.) A northeast/southwest trending lineament, just north of the main grid, was sampled along two profiles perpendicular to the feature, with an increased density of sampling over the feature. The feature generally followed an incised river valley and anomalous CO2 was only detected on the valley floor, where it would be expected as there was lush vegetation in this zone. There were no coincident anomalies for other gases. Soils around two abandoned wells were also sampled. A 16-site grid was surveyed around each well. One well had been completely abandoned and the other was suspended due to failed casing. Such boreholes represent possible points of weakness that may be routes for CO2 migration. The well with failed casing had weakly anomalous CO2 locally to the south, again unmatched for other gases. The fully abandoned well had background CO2 values. Two perpendicular profiles of 10 sites at 25m spacing were sampled for soil gas over the mapped centre of the dissolution feature. Background values were obtained. In 2003 two vertical profiles were performed both indicating an increase in CO2 to a depth maximum of 1.80m; this increase is matched by a corresponding decrease only in O2, indicating biological respiration. Radon concentration indicated no anomalies. Portable gamma spectrometric data was collected in 2003 over the west-centre area of the grid, the profiles and over the control grid. The composition of soils from both areas was found to be very similar.PublishedBerkeley, California4.5. Degassamento naturaleope

Inquinamento diffuso da solventi clorurati negli acquiferi alluvionali dell'Umbria: caratterizzazione e interventi

L\u2019utilizzo di solventi clorurati in varie attivit\ue0 industriali, artigianali e domestiche ha comportato una loro significativa presenza nelle acque sotterranee negli acquiferi alluvionali dell\u2019Umbria e, sulla base di una rete di monitoraggio su un campione di circa n. 900 punti e n. 5000 analisi chimiche nel periodo 1998-2014, \ue8 stato possibile delimitare le zone ad inquinamento diffuso delle acque sotterranee (Alta valle Tevere, Media valle Tevere Nord, Media valle Tevere Sud, Valle Umbra, Conca Eugubina e Conca Ternana). Considerando le modalit\ue0 di migrazione e di degradazione dei composti e la costruzione di un SIT dedicato, sono state classificate quattro tipologie di situazioni: contaminazione dovuta ad un pennacchio con individuazione di una possibile zona sorgente, contaminazione dovuta alla sovrapposizione di diversi pennacchi con possibili diverse zone sorgente, contaminazione dovuta ad un pennacchio senza individuazione di una possibile a zona sorgente e contaminazione diffusa senza individuazione di possibili zone sorgente. Per ognuna delle zone interessate dalle quattro situazioni si sono quindi individuate ulteriori azioni conoscitive e di intervento, compilando una scheda descrittiva completa di dati idrogeologici, idrochimici e di localizzazione dei possibili centri di pericolo. Si \ue8 quindi potuto proporre un piano per affrontare per fasi il problema dell\u2019inquinamento diffuso, con relativi contenuti tecnico-economici e strategie di intervento. Il piano rappresenta un primo esempio a livello regionale, come previsto dalla normativa nazionale e delle altre norme collegate relative alla qualit\ue0 delle risorse idriche e alla bonifica dei siti contaminati

Carbon dioxide degassing and thermal energy release in the Monte Amiata volcanic-geothermal area (Italy)

The quaternary volcanic complex of Mount Amiata is located in southern Tuscany (Italy) and represents the most recent manifestation of the Tuscan Magmatic Province. The region is characterised by a large thermal anomaly and by the presence of numerous CO2-rich gas emissions and geothermal features, mainly located at the periphery of the volcanic complex. Two geothermal systems are located, at increasing depths, in the carbonate and metamorphic formations beneath the volcanic complex. The shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit (Ligurian Unit). A measured CO2 discharge through soils of 1.8 109 mol a 1 shows that large amounts of CO2 move from the deep reservoir to the surface. A large range in d13CTDIC ( 21.07 to +3.65) characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of TDIC allows distinguishing a discharge of 0.3 109 mol a 1 of deeply sourced CO2 in spring waters. The total natural CO2 discharge (2.1 109 mol a 1) is slightly less than minimum CO2 output estimated by an indirect method (2.8 109 mol a 1), but present-day release of 5.8 109 mol a 1 CO2 from deep geothermal wells may have reduced natural CO2 discharge. The heat transported by groundwater, computed considering the increase in temperature from the infiltration area to the discharge from springs, is of the same order of magnitude, or higher, than the regional conductive heat flow (>200 mWm 2) and reaches extremely high values (up to 2700mWm 2) in the north-eastern part of the study area. Heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking. The comparison of CO2 flux, heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining CO2 degassing and heat transfer patterns

Carbon dioxide degassing and thermal energy release in the Monte Amiata volcanic-geothermal area (Italy)

The quaternary volcanic complex of Mount Amiata is located in southern Tuscany (Italy) and represents the most recent manifestation of the Tuscan Magmatic Province. The region is characterised by a large thermal anomaly and by the presence of numerous CO2-rich gas emissions and geothermal features, mainly located at the periphery of the volcanic complex. Two geothermal systems are located, at increasing depths, in the carbonate and metamorphic formations beneath the volcanic complex. The shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit (Ligurian Unit). A measured CO2 discharge through soils of 1.8 109 mol a 1 shows that large amounts of CO2 move from the deep reservoir to the surface. A large range in d13CTDIC ( 21.07 to +3.65) characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of TDIC allows distinguishing a discharge of 0.3 109 mol a 1 of deeply sourced CO2 in spring waters. The total natural CO2 discharge (2.1 109 mol a 1) is slightly less than minimum CO2 output estimated by an indirect method (2.8 109 mol a 1), but present-day release of 5.8 109 mol a 1 CO2 from deep geothermal wells may have reduced natural CO2 discharge. The heat transported by groundwater, computed considering the increase in temperature from the infiltration area to the discharge from springs, is of the same order of magnitude, or higher, than the regional conductive heat flow (>200 mWm 2) and reaches extremely high values (up to 2700mWm 2) in the north-eastern part of the study area. Heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking. The comparison of CO2 flux, heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining CO2 degassing and heat transfer patterns.Published860–8751.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive2.4. TTC - Laboratori di geochimica dei fluidi4.5. Studi sul degassamento naturale e sui gas petroliferiJCR Journalreserve

Regional groundwater flow and interactions with deep fluids in western Apennine: the case of Narni-Amelia chain (Central Italy)

The elemental fluxes and heat flow associated with large aquifer systems can be significant both at local and at regional scales. In fact, large amounts of heat transported by regional groundwater flow can affect the subsurface thermal regime, and the amount of matter discharged towards the surface by large spring systems can be significant relative to the elemental fluxes of surface waters. The Narni-Amelia regional aquifer system (Central Italy) discharges more than 13 m3 sec)1 of groundwater characterised by a slight thermal anomaly, high salinity and high pCO2. During circulation in the regional aquifer, groundwater reacts with the host rocks (dolostones, limestones and evaporites) and mixes with deep CO2-rich fluids of mantle origin. These processes transfer large amounts of dissolved substances, in particular carbon dioxide, and a considerable amount of heat towards the surface. Because practically all the water circulating in the Narni-Amelia system is discharged by few large springs (Stifone-Montoro), the mass and energy balance of these springs can give a good estimation of the mass and heat transported from the entire system towards the surface. By means of a detailed mass and balance of the aquifer and considering the soil CO2 fluxes measured from the main gas emission of the region, we computed a total CO2 discharge of about 7.8 · 109 mol a)1 for the whole Narni-Amelia system. Finally, considering the enthalpy difference between infiltrating water and water discharged by the springs, we computed an advective heat transfer related to groundwater flow of 410 ± 50 MW

Carbon dioxide degassing from Tuscany and Northern Latium (Italy)

The CO2 degassing process from a large area on the Tyrrhenian side of central Italy, probably related to the input into the upper crust of mantle fluids, was investigated in detail through the geochemical study of gas emissions and groundwater. Mass-balance calculations and carbon isotopes show that over 50% of the inorganic carbon in regional groundwater is derived from a deep source highlighting gas−liquid separation processes at depth. The deep carbonate−evaporite regional aquifer acts as the main CO2 reservoir and when total pressure of the reservoir fluid exceeds hydrostatic pressure, a free gas phase separates from the parent liquid and escapes toward the surface generating gas emissions which characterise the study area. The distribution of the CO2 flux anomalies and the location of high PCO2 springs and gas emissions suggest that the storage and the expulsion of the CO2 toward the atmosphere are controlled by the geological and structural setting of the shallow crust. The average CO2 flux and the total amount of CO2 discharged by the study area were computed using surface heat flow, enthalpy and CO2 molality of the liquid phase circulating in the deep carbonate−evaporite aquifer. The results show that the CO2 flux varies from 1×104 mol y−1 km−2 to 5×107 mol y−1 km−2, with an average value of 4.8×106 mol y−1 km−2, about five times higher than the value of 1×106 mol y−1 derived by Kerrick et al. [Kerrick, D.M., McKibben, M.A., Seward, T.M., Caldeira, K., 1995. Convective hydrothermal CO2 emission from high heat flow regions. Chem. Geol. 121, 285–293] as baseline for terrestrial CO2 emissions. The total CO2 discharged from the study area is 0.9×1011 mol y−1, confirming that Earth degassing from Tyrrhenian central Italy is a globally relevant carbon sourc