HAL-BRGM, les publications scientifiques en libre accès du BRGM
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Stability of colloidal gas aphrons based on polymer-surfactant formulations and molecular dynamics insights
No full textInternational audienceColloidal gas aphrons (CGAs) are promising fluids for environmental remediation due to their stability, high viscosity, and effective gas transport. However, previous studies have been limited by narrow concentration ranges, leaving key mechanisms behind bubble stability insufficiently understood. This study systematically explores bubble stability across a wide range of xanthan gum (XG) and sodium dodecyl sulfate (SDS) concentrations (1-10× CMC and 1000-10,000 ppm) using advanced AIassisted image analysis and molecular dynamics (MD) simulations. AI-enhanced microscopy enabled precise quantification of bubble size and morphology, while MD provided molecular-level insights into surfactant-polymer interactions at bubble interfaces. Results showed optimal CGA stability at specific surfactant-polymer ratios, significantly reducing gas diffusion and bubble coalescence. These integrated experimental and computational methods offer valuable guidelines for designing robust CGA-based remediation fluid
Advancing Quantitative Risk Assessment for CO₂ Geological Storage: Experience from the PilotStrategy project
No full textInternational audienceEffective risk management is essential for the safe and responsible deployment of CO₂ geological storage. Within the PilotSTRATEGY project, dedicated efforts are underway to move beyond traditional qualitative approaches and implement quantitative risk assessment methods across multiple prospective storage sites. This poster presents the rationale for this methodological shift, outlines the challenges encountered, and shares early insights from the ongoing work.Quantitative methods offer the potential for more transparent, reproducible, and decision-relevant risk evaluations. However, their implementation in the context of CO₂ storage presents significant hurdles, including data limitations, uncertainty quantification, and the integration of complex geological and operational models. Through this work, we aim to demonstrate that while qualitative assessments remain valuable, they are insufficient on their own for supporting high-stakes decisions about storage site development and operation.The poster will foster discussion around the practicalities of adopting quantitative risk frameworks, the types of decisions they can support, and the conditions under which they add the most value. By sharing lessons learned and open questions, we hope to contribute to a more rigorous and actionable approach to risk management in CO₂ storage
Modélisation de l’effet des phénomènes de bypass sédimentaire sur l’évolution moyen à long terme du trait de côte
No full textUnder the effect of wave-induced currents, sand can be transported around natural or artificial rocky obstacles transverse to the beach through a process called sediment bypassing. This phenomenon plays a key role in beach evolution, particularly in embayed beaches, which are delimited by two rocky obstacles and represent half of the world’s beaches. However, sediment bypassing is often neglected or partially included in shoreline evolution models. The aim of this thesis is to extend the applicability of the reduced-complexity model LX-Shore by implementing a parametrization of sediment bypassing. The new version of the model, which integrates the impact of subaqueous bypassing around obstacles, has been tested on an idealised embayed beach subject to various wave incidence conditions. The results show that accounting for bypassing significantly influences embayed beach planform and shoreline spatial variability, in terms of rotation, curvature, and maximum erosion. Applications to real beaches featuring rocky groynes in Denmark and Fréjus (France) or a longitudinal defense structure in Lacanau (France) have provided insights into the influence of bypassing across different timescales: event-scale, annual-scale, and multi-decadal-scale under the effect of sea level rise. By integrating for the first time a generic parametrization of sediment bypassing into a reduced-complexity model, this work contributes to improving the understanding and modeling of shoreline evolution in the presence of rocky obstacles, offering new perspectives for coastal management.Sous l’effet des courants induits par les vagues, le sable peut contourner les obstacles rocheux naturels ou artificiels présents sur la plage via un phénomène nommé bypass sédimentaire. Le bypass joue un rôle clé dans l’évolution des plages, notamment les plages en baie délimitées par deux obstacles rocheux qui représentent environ la moitié des plages dans le monde. Pourtant, ce phénomène est souvent mal pris en compte dans les modèles d’évolution du trait de côte, voire absent. L’objectif de cette thèse est ainsi d’étendre le champ d’application du modèle à complexité réduite LX-Shore en y implémentant une paramétrisation du bypass sédimentaire. La nouvelle version du modèle, intégrant l’impact du bypass subaquatique, est testée sur une plage en baie idéalisée soumise à diverses conditions de vagues d’incidence variable. Les résultats montrent que la prise en compte du bypass impacte significativement la forme moyenne de la plage et la variabilité spatiale du trait de côte, notamment en termes de rotation, courbure et maximum d’érosion. Des applications sur des plages réelles présentant des épis rocheux (au Danemark et à Fréjus) ou un ouvrage de défense longitudinal (Lacanau) ont permis d’explorer l’influence du bypass à différentes échelles de temps : à l’échelle évènementielle, à l’échelle annuelle et à l’échelle pluri-décennale, sous l’effet de l’élévation du niveau marin. En intégrant pour la première fois une paramétrisation générique du bypass sédimentaire dans un modèle à complexité réduite, ces travaux contribuent à améliorer la compréhension et la modélisation de l’évolution du trait de côte en présence d’obstacles rocheux, offrant ainsi de nouvelles perspectives en termes de gestion des zones côtières
Sediments accumulated in sewer settling basins as recorders of historical use of drugs: potential and limitations
No full textInternational audienceThis study assesses the occurrence of various types of drugs in a sedimentary archive cored in a sewer settling basin with a depth of 14 m. The coring operations were conducted before the basin was drained. A 2.2-m long sedimentary core was recovered. The sediments consisted of successions of coarse minerals and coarse or fine organic layers. One of the main challenges is to be able to date such a very recent archive. This was realized by using an event-based approach with nineteen 14C Carbon dating out of the rising and decay phase of atmospheric 14C content linked to the aerial explosion of thermonuclear bombs (bomb peak). The first results revealed the potential of these sediments to record diverse contaminants. Eighteen of the 20 molecules targeted were quantified at least once. The potential of such archives to record the first use of each drug in the city is questioned, as well as the potential of back-calculated drug consumption on the basis of sedimentary occurrences. The estimated wastewater concentrations fit quite well for some molecules, whereas further work remains necessary for other drug values, especially concerning the back-calculation parameters
Structure crustale 3D et signature géophysique du golfe du Lion
No full textInternational audienceL'héritage des géométries syn-orogéniques dans l'extension post-orogénique est encore peu documenté. Le golfe du Lion offre un cas d'étude où l'initiation du rifting à l'Oligocène se déroule dans un contexte d'arrière-arc peu de temps après une période orogénique, celle des Pyrénées. La période de transition, courte mais structurante, correspond au rift ouest-européen Priabonien, marqué dans le Golfe du Lion — comme souvent dans les chaînes en cours de démantèlement — par la formation de bassins intra-montagneux associés à des décrochements orientés NE-SW, dont certains ont rejoués lors de la phase tectonique tortono-messinienne.A partir d'une nouvelle compilation des anomalies gravimétriques et magnétiques (modifiée d'après Canva et al., 2020) et d'un modèle 3D de la structure crustale du golfe du Lion, nous proposons un nouveau découpage des domaines crustaux, fondé sur leurs signatures géophysiques distinctes. Cette lecture révèle une segmentation marquée de la marge du golfe du Lion. L'analyse permet ainsi de mieux cerner le rôle joué par l'héritage dans la genèse de la marge liguro-provençale
Spatial Gaussian Mixture Model for Geological Predictive Mapping
No full textInternational audiencePredictive mapping is a cornerstone task in geoscience, aiming to identify the spatial distribution of geological features or resources based on indirect or partial observations. It plays a critical role in exploration, environmental assessment, and risk management. Traditionally, supervised machine learning methods have shown promise in this domain, but their performance strongly depends on the availability of labeled training data, a significant limitation in geoscientific contexts where ground truth is sparse or expensive to obtain.To address this, unsupervised learning approaches such as Gaussian Mixture Models (GMMs) offer a compelling alternative by discovering hidden structures in the data without the need for labeled samples. GMMs model the data as a mixture of Gaussian components, each representing a latent cluster with its own mean and variance. However, standard GMMs only consider the attribute space and ignore spatial relationships, which are crucial in geological systems that often exhibit strong spatial coherenceIn this study, we propose a novel spatial extension to GMMs that enhances predictive mapping by incorporating spatial context. Our method adjusts the posterior probabilities of a classical GMM by averaging them over a sliding window across the spatial domain, thereby integrating local neighborhood information while preserving the probabilistic nature of the model. We evaluate the approach on synthetic datasets characterized by clear spatial patterns. Comparative results against classical GMM, classical Kmeans and two state-of-the-art spatial GMM variants (ZHAO et al., 2016; ZHOU et al., 2020) demonstrate the superior ability of our method to produce geologically plausible and spatially consistent predictions
Recycling water, but at what price? The political economy of wastewater reuse
No full textInternational audienceIt is generally assumed that the circular economy generates net benefits; and that these benefits can be fairly accurately measured. Based on the case of treated wastewater reuse (TWWR), this article challenges both assumptions. We argue that economic assessments of TWWR are always deeply political, as they cannot be detached from the promotion and prioritization of particular collective goals. We successively explore: the politics of benefit assessment; the politics of cost assessment; and the politics of costsharing arrangements. We argue that this inescapable political dimension, amplified by wide-ranging economic uncertainties, justifies setting up participatory arenas for each individual project
Cartographie de la favorabilité du sous-sol au déploiement de la géothermie de surface sur une sonde verticale
No full textInternational audienceDans le cadre des missions qui lui sont dévolues par son statut de Service Géologique National, le BRGM a développé un programme pour établir, sur l’ensemble du territoire métropolitain, une cartographie de favorabilité du sous-sol pour la mise en œuvre de sondes géothermiques verticales.Pour ce faire, les équipes du BRGM ont mis en place une méthode d’évaluation de la conductivité thermique moyenne des terrains en se basant sur :•Les données de Test de Réponse Thermique (TRT) disponibles à date, soit 752 TRT.•Les informations de lithologie du sous-sol issues de la base de données des logs géologiques validés (LGV). Pour les besoins du projet, celle-ci a été complétée par la saisie des informations lithologiques de près de 600 forages.•Les informations de la carte lithologique de la France métropolitaine au 1/50000.•Les informations de la carte d’épaisseur de la zone non saturée.Ces différentes données ont servi de données de base à la construction de modèles permettant de calculer par 2 méthodes différentes les valeurs de Conductivité Thermique (CT) sur les zones de massif (Massif armoricain, Massif central et les Vosges) d’une part et sur l’ensemble des bassins sédimentaires d’autre part.Associées aux cartes de températures du sous-sol, ces cartes de CT ont permis d’établir des cartes de favorabilité du sous-sol pour le déploiement de la géothermie de surface sur une sonde verticale pour un usage de chauffage uniquement.Le résultat de ce travail est disponible à la consultation ainsi qu’en téléchargement (sous forme de web services) sur le site www.geothermies.fr.Le travail continu du BRGM de collecte et bancarisation de nouvelles données comme les TRT ou la validation de logs géologiques doit permettre une évolution régulière de ces cartes, dont nous présentons ici une première version
Metasomatic Mineral Systems with IOA, IOCG, and Affiliated Deposits: Ontology, Taxonomy, Lexicons, and Field Geology Data Collection Strategy
No full textInternational audienceMetasomatic iron and alkali-calcic (MIAC) mineral systems form district-scale metasomatic footprints in the upper crust that are genetically associated with iron oxideapatite (IOA), iron oxide and iron sulfide copper-gold (IOCG, ISCG), skarn, and affiliated critical and precious metal deposits. The development of MIAC systems is characterized by series of alteration facies that form key mappable entities in the field and along drill cores. Each facies can precipitate deposit types specific to the facies or host deposits formed at a subsequent facies. Defining the spatial and temporal relations between alteration facies and host rocks as well as with pre, syn, and post MIAC magmatic, tectonic, and mineralization events is essential to understanding the evolution of a MIAC system and to evaluating its overall mineral prospectivity. This paper proposes an ontology for MIAC systems that frames the key characteristics of the main alteration facies described and links it to a taxonomy and descriptive lexicons that allow the user to build an efficient data collection system tailored to the description of MIAC systems. The application developed by the Geological Survey of Canada for collecting field data is used as an example. The data collection system, including the application for collecting field data and the lexicons, are applicable to regional-and deposit-scale geological mapping as well as to drill core logging. They respond to the need for the metallogenic mapping of mineral systems and the development of more robust mineral prospectivity maps and exploration strategies for the discovery of critical and precious metal resources in MIAC system
Lesser Antilles seismotectonic zoning model for seismic hazard assessment
No full textInternational audienceSubduction zones pose a considerable challenge within the realm of seismotectonics, owing to their fault and structure interactions. The Lesser Antilles arc is a good example of how these complexities impact seismic hazard studies with strong along-strike variations in tectonic, seismic, and volcanic activities. While these activities have generated significant damage, the 1839 and 1843 event characteristics (locations, depths, mechanisms, magnitudes) along with their potential implications for megathrust seismicity remain a subject of debate, in particular in the frame of low interseismic coupling. This study is grounded in the compilation of instrumental and historical seismicity and fault catalogs, complemented by analyses of focal mechanisms and rupture types as well as geodetic velocities and strain rates. The resulting seismotectonic zoning model of the Lesser Antilles encompasses the upper plate, subducting oceanic plate, subduction interface, mantle wedge, and volcanoes. We propose a better depth resolution, resulting from recent studies on slab top and upper-plate bottom geometries; a specific area source for the Marie-Galante graben; new propositions for mantle wedge and volcanic zoning; and fully revised area sources for the subduction interface. Our study highlights specific needs for a better seismic hazard assessment in this region