Time filter

Source Type


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.

Kaufhold S.,BGR | Grissemann C.,LBEG | Dohrmann R.,BGR | Klinkenberg M.,Julich Research Center | Decher A.,S and B 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.

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.

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.

Discover hidden collaborations