The Possibility of Extending the Detection Function of an Analytical System to Lower Concentrations

It is shown that the only way to increase the detection capacity of an analytical system is based on the use of the multitude values of the single analytical signal. This can be achieved in two modalities: 1) fixed multitude values (as mean or as sum), and 2) sequential multitude values (as signal sum and as frequencies sum). By using these procedures, the analytical detection can be applied under the classical detection limit at as low concentrations as desired, provided that the multitude of the individual values of the signal be sufficiently high

Porosity and permeability development in compacting chalks during flooding of nonequilibrium brines: Insights from long-term experiment

We report the complete chemical alteration of a Liège outcrop chalk core resulting from a 1072 flow-through experiment performed during mechanical compaction at 130°C. Chemical rock-fluid interactions alter the volumetric strain, porosity, and permeability in a nontrivial way. The porosity reduced only from 41.32% to 40.14%, even though the plug compacted more than 25%. We present a novel analysis of the experimental data, which demonstrates that the geochemical alteration does not conserve the volume of the solids, and therefore, the strain is partitioned additively into a pore volume and solid volume component. At stresses beyond yield, the observed deformation can be explained by grain reorganization reducing the pore space between grains and solid volume changes fromthe rock-fluid interactions. Themechanical and chemical effects are discussed in relation to the observed permeability development.publishedVersio

Geomorphosites and geotourism in Bucharest city center (Romania)

The present paper aims at inventorying the geomophosites in Bucharest as well as introducing geotouristic itineraries that take into account the long-time developed high value cultural heritage of the area. The process included several stages: studying Bucharest’s relief and cultural- historical elements with tourist value from existing bibliography, cartographic methods (aerial photos and different editions of topographic maps), as well as the information gathered from field investigations; identifying and inventorying geomorphosites, assessing the population’s opinion about geoheritage (geomorphosites) and its capitalization in tourism activities, 100 questionnaires were applied; creating geotouristic itineraries and later promoting them. The most valuable and representative geomorphosites identified are: on Colentina Valley (the Plumbuita, Ostrov, Dobroeşti and Pantelimon hills) (aren’t located in the study area), on Dâmboviței Valley (Cotroceni, Șerban Vodă, Mitropoliei, Spirii, Filaret and Arsenal hills, Țăcăliei, Procopoaiei, University terraces, Dâmbovița Meadow). The authors suggest two geotouristic itineraries that emphasize the relationship between the scientific, cultural, and historic elements as well as the human-nature report within the urban area

Subsurface impact of CO2: Response of carbonate rocks and wellbore cement to supercritical CO2 injection and long-term storage. Geologica Ultraiectina (310)

Capture of CO2 at fossil fuel power station coupled with geological storage in empty oil and gas reservoirs is widely viewed as the most promising option for reducing CO2 emissions to the atmosphere, i.e. for climate change mitigation. Injection of CO2 into such reservoirs will change their chemical and mechanical state, for example through acidification of the pore fluid or changes in the state of stress. Similar effects may influence the integrity of overlying caprocks and of old, plugged wells. To fully assess storage system integrity, these effects must be understood. The research reported in this thesis addresses the mechanical and chemical response of carbonate rich reservoir rocks, and of wellbore cements to CO2 injection and storage. State of the-art experimental techniques were employed. These included compaction experiments on simulated porous carbonates in order to investigate time-dependent compaction phenomena, compression tests to determine the mechanical failure behaviour of chalks and wellbore cements, and reaction experiments to explore the long-term chemical effects of CO2 on cement. The results show that CO2 can accelerate long-term compaction. However, under the saline conditions of typical limestone reservoirs, the effect will be negligible if the reservoir was stable before CO2 injection. Highly porous chalks are well known to be unstable to water injection. However CO2 has little further effect. Results obtained for wellbore cement (Class A Portland cement) similar to the cements used in depleted Dutch gas fields, such as the De Lier field, showed that the stress changes accompanying injection will not lead to mechanical damage. In addition, experiments on chemical interaction have shown that reaction of CO2 with the cement precipitates calcium carbonate into voids and cracks, thus improving the sealing properties. Provided such wells are plugged properly upon abandonment, mechanical and chemical integrity will be preserved