ALBERT

Description: 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.

Description: Istituto Nazionale di Geofisica e Vulcanologia

Description: Submitted

Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive

Description: JCR Journal

Description: open

Description: EnCana’s CO2 injection EOR project at Weyburn (Saskatchewan, Canada) is the focal point of a multi-faceted research program, sponsored by IEA GHG R&D and numerous international industrial and government partners including the European Community (BGS, BRGM, INGV and GEUS research providers), to find co-optimization of “CO2-EOR Production” and “CO2 -Geological Storage”, addressed to environmental purposes, in the frame of the Kyoto Agreement Policies. The Weyburn oil-pull is recovered from Midale Beds (at the depth of 1300-1500 m). This formation consists of Mississipian shallow marine carbonate-evaporites that can be subdivided into two units: i) the dolomitic “Marly” and ii) the underlying calcitic “Vuggy”, sealed by an anhydrite cap. Presently, around 3 billions mc of supercritical CO2 have been injected into the “Phase A1”injection area that includes around 90 oil producers, 30 water injectors and 30 CO2 injection wells, build up since September 2000. INGV has carried out a geochemical monitoring programme -approximately thrice yearly from pre-injection (“Baseline” trip, August 2000) to September 2004- performing trace element and dissolved gas analysis along with fluids sampling surveys, the latter being performed by the Canadian partners. The experimental data are the base of a geochemical modelling, i.e. the main goal of the present study. In the past, assumptions and gap-acceptance have been made in the literature in the frame of the geochemical modelling of CO2 geological storage, in order to reconstruct the reservoir conditions (pressure, pH and boundary conditions). As these parameters of deep fluids cannot be measured in-situ, all this information must be computed by a a posteriori procedure involving the analytical data. In this work we proposed an approach to geochemical modeling in order to:: i) reconstruct the in-situ reservoir chemical composition (including pH) and ii) evaluate the boundary conditions (e.g. pCO2, pH2S), necessary to implement the reaction path modelling. This is the starting point to assess the geochemical impact of CO2 into the oil reservoir and, as main target, to quantify water-gas-rock reactions. Our geochemical modelling procedure is based on the available data such as: a) bulk mineralogy of the Marly and Vuggy zones; b) average gas-cap composition and c) pre-and post-CO2 injection selected water samples from Midale Beds. The PRHEEQC (V2.11) Software Package was used to reconstruct the in-situ reservoir composition by calculating the chemical equilibrium among the various phases at reservoir temperature (60°C) and pressure (150 bars) conditions by suitable thermodynamic corrections to code database. Then, we identified possible compositions of the initially reservoir liquid phases, always taking into account the case histories of the Marly and Vuggy units. The inverse modelling simulation (IMS) was then performed in order to calculate the amounts of mass transfer of liquid, gas and solid phases that accounted for changes in the water chemistry between the 2000 and 2003 data-sets. IMS calculations suggest that the reservoir underwent mineralogical changes, such as precipitation of chalcedony, gypsum and kaolinite and dissolution of anhydrite and k-feldspar. Calcite dissolution is predicted, but the precipitation of others carbonates (dolomite, dawsonite and siderite) can also occur. Finally, we modelled the geochemical impact of CO2 injection on Weyburn reservoir subjected to both local equilibrium and kinetically controlled reactions. All experimental data and thermo-kinetic modeling of the evolution of the CO2-rich Weyburn brine interacting with host rock minerals performed over 100 years after injection confirm that “solubility trapping” is prevailing in this early stage of CO2 injection. Further and detailed studies on the evolution of the CO2-rich Weyburn brine is one of main aims of this study in the framework of a PhD programme between the INGV of Rome and the Department of Earth Sciences of Florence.

Description: Published

Description: Berkeley, California

Description: 2.4. TTC - Laboratori di geochimica dei fluidi

Description: open

Description: CO2 Capture & Storage (CCS) is presently one of the most promising technologies for reducing anthropogenic emissions of CO2 . Among the several potential geologi- cal CO2 storage sites, e.g. depleted oil and gas field, unexploitable coal beds, saline aquifers, the latter are estimated to have the highest potential capacity (350-1000 Gt CO2 ) and, being relatively common worldwide, a higher probability to be located close to major CO2 anthropogenic sources. In these sites CO2 can safely be retained at depth for long times, as follows: a) physical trapping into geologic structures; b) hy- drodynamic trapping where CO2(aq) slowly migrates in an aquifer, c) solubility trap- ping after the dissolution of CO2(aq) and d) mineral trapping as secondary carbon- ates precipitate. Despite the potential advantages of CO2 geo-sequestration, risks of CO2 leakage from the reservoir have to be carefully evaluated by both monitoring techniques and numerical modeling used in “CO2 analogues”, although seepage from saline aquifers is unlikely to be occurring. The fate of CO2 once injected into a saline aquifer can be predicted by means of numerical modelling procedures of geochemical processes, these theoretical calculations being one of the few approaches for inves- tigating the short-long-term consequences of CO2 storage. This study is focused on some Italian deep-seated (〉800 m) saline aquifers by assessing solubility and min- eral trapping potentiality as strategic need for some feasibility studies that are about to be started in Italy. Preliminary results obtained by numerical simulations of a geo- chemical modeling applied to an off-shore Italian carbonatic saline aquifer potential suitable to geological CO2 storage are here presented and discussed. Deep well data, still covered by industrial confidentiality, show that the saline aquifer, includes six Late Triassic-Early Jurassic carbonatic formations at the depth of 2500-3700 m b.s.l. These formations, belonging to Tuscan Nappe, consist of porous limestones (mainly calcite) and marly limestones sealed, on the top, by an effective and thick cap-rock (around 2500 m) of clay flysch belonging to the Liguride Units. The evaluation of the potential geochemical impact of CO2 storage and the quantification of water-gas-rock reactions (solubility and mineral trapping) of injection reservoir have been performed by the PRHEEQC (V2.11) Software Package via corrections to the code default ther- modynamic database to obtain a more realistic modelling. The main modifications to the Software Package are, as follows: i) addition of new solid phases, ii) variation of the CO2 supercritical fugacity and solubility under reservoir conditions, iii) addi- tion of kinetic rate equations of several minerals and iv) calculation of reaction sur- face area. Available site-specific data include only basic physical parameters such as temperature, pressure, and salinity of the formation waters. Rocks sampling of each considered formation in the contiguous in-shore zones was carried out. Mineralogy was determined by X-Ray diffraction analysis and Scanning Electronic Microscopy on thin sections. As chemical composition of the aquifer pore water is unknown, this has been inferred by batch modeling assuming thermodynamic equilibrium between minerals and a NaCl equivalent brine at reservoir conditions (up to 135 ̊C and 251 atm). Kinetic modelling was carried out for isothermal conditions (135 ̊C), under a CO2 injection constant pressure of 251 atm, between: a) bulk mineralogy of the six formations constituting the aquifer, and b) pre-CO2 injection water. The kinetic evolu- tion of the CO2 -rich brines interacting with the host-rock minerals performed over 100 years after injection suggests that solubility trapping is prevailing in this early stage of CO2 injection. Further and detailed multidisciplinary studies on rock properties, geochemical and micro seismic monitoring and 3D reservoir simulation are necessary to better characterize the potential storage site and asses the CO2 storage capacity.

Description: Published

Description: Vienna (Austria)

Description: 2.4. TTC - Laboratori di geochimica dei fluidi

Description: open