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Kaufhold S.,BGR | Dohrmann R.,BGR | Groger-Trampe J.,LBEG
Corrosion Engineering Science and Technology | Year: 2017

Copper pellets were reacted with different solutions, reference minerals, and well-characterised bentonites to investigate the effect of different bentonites on the stability of native copper in repository concepts for high-level radioactive waste. The reaction of Cu in contact with bentonite used as barrier material to store high-level radioactive waste was significantly affected by the presence of sulphides (e.g. pyrite) leading to a specific corrosion. Bentonites free of pyrite are not actively involved in a reaction with Cu. Nevertheless, slightly different Cu mass losses were found for different bentonites. For different bentonites, different coatings were found on the Cu surface. The characteristics of these coatings are probably responsible for different Cu mass losses of Cu in contact with different bentonites. As an example, particularly dense coatings led to a decrease in Cu mass loss. No relation of the Fe-corrosivity of different bentonites with Cu mass loss was found, which proves that the Fe-corrosion mechanism differs from the Cu-corrosion at the metal/bentonite interface. The experiments also demonstrated the importance of the presence even of traces of oxygen. © 2017 Institute of Materials, Minerals and Mining Published by Taylor & Francis on behalf of the Institute

Kaufhold S.,BGR | Grissemann C.,LBEG | Dohrmann R.,BGR | Klinkenberg M.,Jülich Research Center | Decher A.,SandB Industrial Minerals GmbH
Clays and Clay Minerals | Year: 2014

Electrical measurements are used in various fields of geoscience and technology, e.g. gas/oil exploration or landslide-barrier monitoring. Although clays are amongst the most conducting geomaterials their electrical properties are not yet fully understood. For example, in a recent high-levelradioactive- waste repository large-scale test, a bentonite barrier was monitored geoelectrically. To facilitate interpretation of the results, the reasons for the observed differences in the electrical conductivity must be understood (e.g. changes in water content, temperature, salinity of pore water, etc.). To improve understanding of the electrical properties of clay minerals, in situ measurements must be combined with laboratory measurements. In situ measurements allow the characterization of the material in its natural state and laboratory measurements, for small sample amounts, allow the user to vary relevant parameters systematically such as water content, temperature, the salinity of the pore water, or even the cation population if swelling clay minerals are present. In situ measurements using different electrode distances, from m to cm range, proved that small-scale investigations are essential because of small-scale material heterogeneities. In the laboratory, all the relevant parameters mentioned above can be controlled more easily for small sample amounts. In the present study three different small-scale devices (SSM1 - SSM3) were compared. The geometry factor, K, was determined both by calculation and by a calibration against solutions of different conductivity. Calculated and measured geometry factors were in good agreement. SSM1 and SSM2 - both with four pin-shaped electrodes - were found to be particularly applicable for in situ measurements. SSM2, with point contacts at the tips of the pins, was considered to be an improvement over SSM1 because the effects of both water content and temperature gradients (which are particularly relevant near the surface) were less pronounced using SSM2. SSM3, in which the contacts are placed at the bottom of a 4.5 mL trough, proved to be useful when systematically varying all of the parameters influencing the electrical properties in the laboratory.

Kaufhold S.,BGR | Stanjek H.,RWTH Aachen | Penner D.,ZHAW Zurich University of Applied Sciences | Dohrmann R.,LBEG
Clay Minerals | Year: 2011

Suspensions of thirty six bentonites were equilibrated for 24 h and then adjusted to pH 3. After an hour, pH titrations up to pH 12 at varying ionic strengths were performed within 4.5 h. The titration data were recalculated into proton affinity distributions (PAD) using the condensed approximation. In spite of widely varying chemical compositions, all bentonites showed a protonation reaction between pK 4 and 5, which could be assigned to aluminol groups at the edge surfaces of the smectites. The average pK is 4.73±0.31. A second prominent peak in the PAD at pK = 10.43±0.13 could be assigned to exchangeable Mg 2+ in the interlayer space. The possibility to constrain both pK values at a fixed average value will decrease the number of parameters in surface complexation modelling and thus enhance its convergence. © 2011 Mineralogical Society.

Pusch G.,Clausthal University of Technology | Ionescu G.F.,Clausthal University of Technology | May F.,BGR | Voigtlander G.,GDF SUEZ | And 2 more authors.
Erdoel Erdgas Kohle | Year: 2010

Underground gas storage (UGS) and CO2 storage in depleted gas reservoirs have several common technical, reservoir mechanic and operative features. However, the media involved, HC gases and CO2. are physically and chemically different. The greenhouse gas CO2 forms a corrosive acid when dissolved in water. This can react with mineral compounds of the storage and cap rock and may change the hydraulic properties in different ways. A discussion on the common features of underground gas storage and CO2 storage covers the permeability of clay or shale reservoir intercalations for gas; enhancing the rest gas recovery (EGR) in depleted reservoirs; limitations of the EGR capacity; hydrocarbon (HC) fuels as the backbone for the global energy supply until renewable energy resources become technically and economically mature to replace them; linking constant production streams with varying demand; relevance of the underground storage in the natural gas sector for safe and sustainable gas delivery process; technology issues; physical properties of media for UGS and CO2 storage; fluid-rock Interactions in UGS and CO2 storage; reservoir performance for UGS and CO2 storage; and process simulations.

Pusch G.,Clausthal University of Technology | Ionescu G.F.,Clausthal University of Technology | May F.,Clausthal University of Technology | Voigtlander G.,GDF SUEZ | And 2 more authors.
Oil Gas European Magazine | Year: 2010

Underground gas storage and CO2 storage in depleted gas reservoirs have many common technical, reservoir mechanic and operative features, but the media involved, HC gases and CO2, are physically and chemically different. CO2 dissolved in water forms a corrosive acid, which can react with mineral compounds of the storage and cap rock and may change the hydraulic properties in different ways. Depending on the original rock composition, carbonate, feldspar and chlorite cements may be corroded and dolomite can be precipitated. Clay or shale reservoir intercalations may become more permeable for gas. However these changes will likely not happen near the injection wells but far away, because of residence time and water saturation needed for the reactions. Favorable physical properties of CO2 (density, viscosity, compressibility) will contribute in enhancing the rest gas recovery (EGR) in depleted reservoirs. The EGR capacity is limited by the termination of HC production after CO2 breakthrough. Some 3 to 10% of the IGIP may be recovered additionally to the natural depletion yield. Anticline trap types with steep flanks are favorable compared to flat stratigraphic traps. High production rates accelerate the EGR. Primary injection until the reservoir pressure is raised to a medium level, followed by the EGR phase is unfavorable compared with simultaneous injection/production from the beginning. © 2010 URBAN-VERLAG Hamburg/Wien GmbH.

Pierau R.,LBEG
3rd Sustainable Earth Sciences Conference and Exhibition: Use of the Sub-Surface to Serve the Energy Transition | Year: 2015

Two potential sandstones units are present in the Lower Crteaceous in the Lower Saxony Basin. The "Valendis-Sandstone" of Valanginian age could be a primary target for geothermal use. On a regional scale, the sandstone units of the Isterberg Formation of Berriasum age in the central part of the LSB barely meet the minimum requirements for geothermal use. Nevertheless, suitable aquifer conditions may be developed on a local scale.

Dill H.G.,Bundesanstalt fur Geowissenschaften und Rohstoffe | Dohrmann R.,LBEG | Kaufhold S.,Bundesanstalt fur Geowissenschaften und Rohstoffe
Applied Clay Science | Year: 2011

Disseminated and faultbound argillic alteration is widespread in (sub)volcanic domes and dykes of the Late Variscan Saar-Nahe Basin, SW Germany. It is accompanied by small but now exhausted Cu, Hg and Ag deposits. Upper Carboniferous to early Permian basaltic andesites through trachyandesites host ferroan saponite, a product of autohydrothermal alteration This alteration affected mafic minerals, e.g., pyroxene, amphibole, and biotite as well as feldspar and took place at a shallow depth underneath the zone of oxidation at temperatures below 100 °C-150 °C in the pH range from pH 7 to pH 5.5. Chlorite preceded saponitization under more alkaline conditions, while quartz and kaolinite post-dated it under more acidic and reducing conditions. Oxidizing conditions provoked hematite (plus jarosite) to develop. Saponite forms part of a slow-cooling argillic alteration system with a low potential to develop Cu-Au-Ag deposits of its own. Rapid cooling under near-ambient conditions under oxidizing and more acidic conditions prevented the wide range of Mg-Fe-bearing clay minerals from forming and might have ended up in the formation of kaolinite plus nontronite, APS and ore minerals. Ferroan saponite has some relevance in terms of economic geology as far as the industrial minerals and rocks are concerned. Autohydrothermal ferroan saponite in andesitic rocks is related in time and space to the creation of amygdules which are filled with amethyst and zeolites Saponite is thus decisive for the rock strength of these magmatic rocks, which are quarried for aggregates and/or dimension stones. While a useful tool to assess the quantity of saponite in these rocks, measuring the CEC does not provide a full picture of the rock strength. The latter can only be determined when the structural types of saponitization are considered in context with the cations present in the lattice of saponite. Rocks containing isolated patches of saponite are less vulnerable than magmatic rocks with stockwork-like saponite. In the latter water may get in touch with saponite and induce a swelling which, in turn, creates a negative effect on the rock strength. © 2010 Elsevier B.V.

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