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Inproceedings Reference Using Fibre-Optic DAS surveying to de-risk a shallow geothermal energy storage site in Brussels, Belgium
Europe is working hard to meet its first climate goals. With High Temperature Aquifer Thermal Energy Storage (HT-ATES) large quantities of green energy can be stored in the subsurface in the form of heat. It is important that a site is characterised well as leakage from the reservoir would degrade the efficiency of the system, and could also endanger potable water supplies. Seismic imaging is currently the method with highest resolution and the largest de-risking capability for geothermal projects. This study pursues the use of fibre-optic distributed acoustic sensing (FO-DAS) technology in seismic acquisition to improve the de-risking ability of seismic data in urban HT-ATES settings. In 2019 TNO and GSB combined a dense surface based high resolution seismic survey with a FO-DAS VSP survey on a potential ATES site in the city of Brussels, Belgium. Besides the technology demonstration, targets were aquifer + seal continuity and depth away from the well as well as acoustic velocity of the sediment overburden for H/V Spectral Ratio calibration. The intermediate result indicates that with FO-DAS it is possible to image the subsurface relatively easy, fast, at low cost and with low environmental impact, even in busy seismically noisy urban areas.
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference BrugeoTool: “All in One” Professional Geoscientific Tool of Brussels.
Key words: Shallow geothermal, Resources assessment, Geoscientific tool, Brussels Since 2015, the interest in installing shallow geothermal systems has significantly increased in Brussels Capital Region (BCR). However, limited knowledge of ground conditions, lack of public awareness and an urban context restrict the development of shallow geothermal systems in the BCR despite the high potential of this technique in the area. The BRUGEO project was launched thanks to ERDF funding and aims to facilitate accessibility and the efficient use of shallow geothermal energy in the Brussels region. In this four years project (2016-2020), specific actions promoting the geothermal potential of the BCR are addressed: 1- Collect existing data related to the knowledge on Brussels subsurface (geological, hydrogeological, and geothermal data); 2- Conduct new laboratory and field tests in order to complete geological analyses and to assess geothermal parameters; 3- Map the geothermal potential for open and closed systems. The BrugeoTool was developed in 2020 conjointly with Brussels Environment and intends to be a useful tool at any stage of the process of a geothermal project for citizens, project managers as well as for experts. From the project manager side, BrugeoTool provides information on geothermal potential for open and closed systems, plans and controls the stages of a geothermal project, analyzes environmental constraints and helps to prepare the application for an environmental permit, and predesigns a geothermal installation using the Smartgeotherm tool developed by the Belgian Building Research Center. From the expert point of view, BrugeoTool allows to consult geological, hydrogeological, geothermal and environmental data in the form of maps (2D), it automatically draws up a lithostratigraphic (1D) log synthesizing the geological, hydrogeological and geothermal parameters, explores the Brustrati3D geological model (3D), evaluates the (pre) feasibility of a shallow (<300 m) vertical geothermal project for open or closed systems and carries out its pre-sizing. Finally, this webtool lets the citizens to familiarize themselves with the geology and hydrogeology of Brussels and its environmental context.
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference A posteriori verification methodology for astrochronology: a step further to improve the falsifiability of cyclostratigraphy
Cyclostratigraphy is increasingly used to improve the Geologic Time Scale and our understanding of past climatic systems. However, except in a few existing methodologies, the quality of the results is often not evaluated. We propose a new methodology to document this quality, through a decomposition of a signal into a set of narrow band components from which instantaneous frequency and amplitude can be computed, using the Hilbert transform. The components can be obtained by Empirical Mode Decomposition (EMD), but also by filtering a signal (be it tuned or not) in any relevant way, and by subsequently performing EMD on the signal minus its filtered parts. From that decomposition, verification is performed to estimate the pertinence of the results, based on different concepts that we introduce: Integrity quantifies to what extent the sum of the components is equal to the signal. It is defined as the cumulated difference between (1) the signal, and (2) the summed components of the decomposition. EMD fulfils integrity by design, except for errors caused by floating-decimal arithmetic. Ensemble Empirical Mode Decomposition (EEMD) may fail to satisfy integrity unless noisy realisations are carefully chosen in the algorithm to cancel each other when averaging the realisations. We present such an algorithm implemented in R: “extricate”, which performs EEMD in a few seconds. Parsimony checks that the decomposition does not generate components that heavily cancel out. We propose to quantify it as the ratio between (1) the cumulated absolute values of each component (except the trend), and (2) the cumulated absolute values of the signal (minus the trend). The trend should be ignored in the calculation, because an added trend decreases the parsimony estimation of a similar decomposition. IMF departure (IMFD) quantifies the departure of each component to the definition of intrinsic mode functions (IMF), from which instantaneous frequency can reliably be computed. We define it as the mean of the absolute differences of the base 2 logarithms of frequencies obtained using (1) a robust generalized zero-crossing method (GZC, which simplifies the components into extrema separated by zero-crossings) and (2) a more local method such as the Hilbert Transform. Reversibility is the concept that all initial data points are preserved, even after linear interpolation and tuning. This allows to revert back to the original signal and discuss the significance of each data point. To facilitate reversibility we introduce the concept of quanta (smallest depth or time interval having significance for a given sampling) and an algorithm computing the highest rational common divisor of given values in R: “divisor”. This new methodology allows to check the final result of cyclostratigraphic analysis independently of how it was performed (i.e. a posteriori). Once the above-mentioned concepts are taken into account, the instantaneous frequencies, ratios of frequencies and amplitudes of the components can be computed and used to interpret the pertinence of the analysis in a geologically meaningful way. The instantaneity and independence of frequency and amplitude so obtained open a new way of performing time-series analysis.
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference StratigrapheR: making and using lithologs in R
StratigrapheR is an open-source integrated stratigraphy package. It is available in the free software environment R (https://CRAN.R-project.org/package=StratigrapheR) and is designed to generate lithologs in a semi-automated way, to process stratigraphical information, and to visualize any plot along the lithologs in the R environment. The basic graphical principle behind StratigrapheR is the incremental addition of elements to a drawing: a plot is opened, and graphical elements are successively added. This allows compartmentalisation of the drawing process, as well as the superposition of different plots for comparison. For instance a litholog of a single section can be written as a single function including all the drawing sub-functions, and be integrated in a larger plot, for instance to be correlated to other sections or to show proxy data. The StratigrapheR package is designed for efficient work, and minimum coding, while still allowing versatility. The lithological information of beds (upper and lower boundary, hardness, lithology, etc.) is converted into polygons. All polygons are drawn together using a single function, and each polygon can have its personalised symbology allowing to distinguish lithologies. A similar workflow can be used for plotting proxies while distinguishing each sample by their lithology. Vector graphics can be imported as SVG files, and precisely drawn with the lithologs to serve as symbols or complex elements. Every type of symbol is plotted by calling one single function which repeats the drawing for each occurrence of the represented feature. This illustrates that the amount of work invested to make lithologs using StratigrapheR is related to their complexity rather than their length: a long but monotonous litholog (e.g. of marl-limestone alternations) only takes a few lines of code to generate. The StratigrapheR package also provides a set of functions to deal with selected stratigraphic intervals (for instance in the [0,1[ form): they allow simplification, merging, inversion and visualisation of intervals, as well as identifying the samples included in the given intervals, and characterising the relation of the intervals with each other (overlap, neighbouring, etc.). StratigrapheR includes PDF and SVG generation of plots, of any dimension. The generated PDF can even store multiple plots in a single file (each plot on a different page) to document data processing comprehensively.
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference The geoarchaeology of south Qatar
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference Metagenomics of tsunami deposits: developments, challenges and recommendations from a case study on the Shetland Islands (UK)
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference Der südliche Bergstraßenneckar im Oberrheingraben: Erste Ergebnisse zur fluvialen Aktivität, Ver-landung und anthropogenen Überprägung
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference Dynamisches Klima und weichende Küsten im Nahen Osten – Grundlagen der biblischen Sintflut?
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference Where and why: using a structural framework to contextualise and improve the understanding of processes leading to mineral occurrences
The societal development towards climate neutrality and the ambition for economic growth and well-being in Europe rely on mineral raw materials. Mineral occurrences can be seen as manifestations of specific geological processes that happened in the subsurface, or geomanifestations. Locating and better understanding mineral occurrences and deposits in Europe is crucial for future informed decision making on local resourcing. The GeoConnect³d project is developing a multi-scale structural framework in which geological maps and 3D models can be inserted and related to. In our novel approach, the structural framework reorganises geological information in terms of geological limits and geological units. Limits are defined as broadly planar structures that separate a given geological unit from its neighbouring units, e.g. faults (limits) that define a graben (unit), or an unconformity (limit) that defines a basin (unit). Geomanifestation data are then added to the structural framework model aiming to show where and how processes and structures may be linked. This approach was tested in Belgium, where a structural framework was created at different scales, from most detail at 1:250,000 to more generalised at 1:2,000,000. Mineral occurrence data from the Minerals4EU database were used to test the model. As an example, a spatial link between Pb-Zn deposits and structural framework elements is identifiable in the Herve-Vesdre and Landenne areas. Although the deposits are located within the Variscan orogenic front, deposition is post-Variscan and spatially associated with transverse NNW-SSE faults part of the Rhine graben network (Dejonghe, 1998). With a combination of database attributes and SKOS vocabulary, the information of deposition age and time of activity of faults displayed in the structural framework helps to quickly place these deposits in the context of the Lower Rhine embayment. Therefore, the structural framework can translate highly technical scientific knowledge by using an interactive tool that presents information in a more understandable way. We consider the outcomes of this test promising to fulfil one of the main goals of GeoConnect³d: preparing and disclosing geological information in a way it is more useful for stakeholders. We also consider this as the way forward towards pan-European integration and harmonisation of geological information, where the ultimate challenge is to correlate or otherwise link information from different geological domains and of different scales. This will be beneficial for the identification and better geological understanding of European mineral resources. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166. Reference: Dejonghe, L., 1998. Zinc-lead deposits in Belgium. Ore Geology Reviews 12, 329-354.
Located in Library / RBINS Staff Publications 2020
Inproceedings Reference Naturally CO2-rich water springs in Belgium evidencing complex subsurface interactions
Numerous naturally CO2-rich mineral water springs, locally called ‘pouhons’, occur in southeast Belgium. These are oversaturated in CO2 (up to 4g/L) and have attracted economic, touristic and scientific interest for centuries. Water sources occur within Palaeozoic rocks of the Rhenohercynian deformation zone, a fold-and-thrust belt at the north of the Variscan orogeny in central Europe. Many occurrences are concentrated in the Cambro-Ordivician Stavelot-Venn massif. A widely accepted model, supported by H-O isotopic signatures, is that sources are primarily fed by meteoric water, which infiltrates through Quaternary sediments, then reaching Lower Palaeozoic rocks to meet the mineral and CO2 source at unknown depth. Different ideas for the origin of CO2 are grouped in two main hypotheses: a) generation by dissolution of carbonate rocks and/or nodules, and b) volcanic degassing related to the neighbouring Eifel area in Germany. These well-known interpretations are mostly based on geochemical studies that are dispersed and poorly accessible. These have now been gathered in the light of new sampling campaigns, allowing to revisit and compare the views of earlier authors. We also for the first time include the geotectonic setting of the region. Carbonate rocks in the region are represented by Lower Carboniferous and Middle Devonian limestones. Depending on the assumed structural evolution for this foreland fold-an-thrust belt, these may occur at >2 km depth below the Stavelot-Venn massif. Carbonate nodules are present in other formations, but their limited volume is unlikely to originate high and long-lived quantities of CO2. Springs enriched in CO2 are also common in the volcanic Eifel area, with presence of mantle CO2 well established. The supposed extension of the Eifel plume would allow for a magmatic CO2 source below the Stavelot-Venn massif from degassing of the plume (>50 km deep), or of an unknown shallower magmatic reservoir. Available stable and noble isotopes point to a mixed carbonate-magmatic origin. If considering the presence of limestones at depth, meteoric water should infiltrate at least 2 km. Known deep-rooted faults are thought to act as preferential groundwater pathways. However, such deep circulation is incompatible with the low temperatures of springs (~10oC), unless the ascent is slow enough to fully dissipate heat prior to resurfacing. Another possibility is that meteoric water does not infiltrate as deep, with CO2 being transported upwards to meet groundwaters at shallower depths. The presence of CO2 surface leaks, locally called ‘mofettes’, could be evidence of such relatively shallow availability of CO2. The evaluation of existing hypotheses highlights complex subsurface processes that involve water infiltration, CO2 assimilation and water resurfacing in southeast Belgium. As such, this review is an important guide for the newly launched sampling campaigns. This work is part of two research projects: GeoConnect³d-GeoERA that has received funding by the European Union’s Horizon 2020 research and innovation programme under grant agreement number 731166, and ROSEAU project, as part of the Walloon program « Doctorat en Entreprise », co-funded by the SPW Région Wallonne of Belgium and the company Bru-Chevron S.A. (Spadel group), under grant number 7984.
Located in Library / RBINS Staff Publications 2020