HAL-BRGM, les publications scientifiques en libre accès du BRGM
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: Comment le changement climatique pourrait affecter le devenir des polluants pétroliers des sols
No full textNational audienceDans un contexte de changements climatiques (où des évènements de précipitations plus extrêmes et de plus fortes intensités de variations saisonnières du niveau des nappes phréatiques sont attendus), ce projet a pour objectif de mieux comprendre l’impact de l’intensité des variations du niveau des nappes phréatiques sur le comportement d’un sol pollué par des hydrocarbures légers en phase non aqueuse (LNAPLs). Pour cela, des expériences sur colonnes lysimétriques ont été mises en place afin de suivre l’effet de différents scénarios de précipitations et de variations de niveau piézométrique sur les propriétés du sol (pH, Eh, teneur en eau), la nature et la quantité de polluants relargués depuis le sol pollué vers la phase gazeuse (GC-MS, micro-GC) et la phase dissoute (GC-TQD). Les résultats montrent que l’augmentation de l’intensité des variations du niveau de la nappe engendre un étalement plus important des LNAPLs dans le sol, favorisant le relargage des hydrocarbures vers la phase dissoute et la phase gazeuse. Ainsi, les conditions attendues du changement climatique pourraient accroître la mobilité des LNAPLs, augmentant leur impact environnemental à court terme
Characterisation of deep reservoirs for geothermal application: development of a proof of concept in the Loiret department (Centre-Val de Loire region, France)
No full textInternational audienceThe geological and hydrogeological knowledge of deep geothermal reservoirs in French sedimentary basins differs significantly depending on the previous exploration carried out (mostly for hydrocarbon exploration). Currently, the geothermal development for heat production in France is mainly concentrated in Ile-de-France and Nouvelle-Aquitaine regions. To encourage the development of deep geothermal energy projects in other aquifers and geographical areas, a better knowledge of the geometry and properties of the geothermal resources is needed by reprocessing existing data acquisition from oil exploration (drilling, seismic campaigns), and data from geothermal or water resources exploitation. In this context, BRGM has been commissioned by the General Direction of Climate and Energy (DGEC) to coordinate a national geothermal inventory. The first year (2023-2024) has enabled an initial proof of concept with a review and analysis of hydrocarbon data to characterise the geothermal potential of the deep reservoirs (> 500m) belonging to the Oxfordian, Dogger and Triassic units in the Loiret department of the Paris basin. Well log analyses were conducted on 46 wells (45 hydrocarbon, 1 geothermal) and a set of 12 wells were selected for quantitative interpretation and petrophysical model. About 1930 km of vintage seismic data where reprocessed, applying a processing sequence that best reflect the subsurface geometry and preserve the seismic amplitudes, allowing to use them for quantitative interpretation.A specific workflow was developed for characterising the deep geothermal reservoirs. In a first stage, deposit environments (rock-types) were defined for each kind of reservoir (carbonates, sandstones) based on log interpretation and using stratigraphic well correlations. In a second stage, a 3D geological model was build using the horizons from the seismic interpretation converted to depth and filled with deposit environments using a stochastic approach. In a third stage, statistical analyses were performed to extract favourability maps from the 3D model for each reservoir. The favourability maps define the probability to intercept a facies with reservoir properties. In addition, maps of depth, temperature, total and net thickness were defined. The workflow was completed with quantitative interpretations (volume of clay, total and effective porosity) along 2D seismic lines (600 km among the 1930 km). This work is pursuing in 2024-2025 for the entire region of Centre-Val de Loire and Picardie in the Paris basin.La connaissance géologique et hydrogéologique des réservoirs géothermiques profonds dans les bassins sédimentaires français diffère considérablement en fonction de l'exploration antérieure effectuée (principalement pour la recherche d'hydrocarbures). Actuellement, le développement de la géothermie pour la production de chaleur en France est principalement concentré dans les régions d'Ile-de-France et de Nouvelle-Aquitaine. Pour favoriser le développement de projets de géothermie profonde dans d'autres aquifères et zones géographiques, une meilleure connaissance de la géométrie et des propriétés des ressources géothermiques est nécessaire en retraitant les données existantes issues de l'exploration pétrolière (forages, campagnes sismiques), et les données issues de l'exploitation des ressources géothermiques ou en eau. Dans ce contexte, le BRGM a été missionné par la Direction Générale du Climat et de l'Énergie (DGEC) pour coordonner un inventaire géothermique national. La première année (2023-2024) a permis de réaliser une première preuve de concept avec une revue et une analyse des données hydrocarbures pour caractériser le potentiel géothermique des réservoirs profonds (> 500m) appartenant aux unités de l'Oxfordien, du Dogger et du Trias dans le département du Loiret du bassin parisien. Des analyses de diagraphies ont été effectuées sur 46 puits (45 puits d'hydrocarbures, 1 puits géothermique) et un ensemble de 12 puits a été sélectionné pour une interprétation quantitative et un modèle pétrophysique. Environ 1930 km de données sismiques anciennes ont été retraitées, en appliquant une séquence de traitement qui reflète au mieux la géométrie du sous-sol et préserve les amplitudes sismiques, ce qui permet de les utiliser pour l'interprétation quantitative. Un processus spécifique a été développé pour caractériser les réservoirs géothermiques profonds. Dans un premier temps, les environnements de dépôt (types de roches) ont été définis pour chaque type de réservoir (carbonates, grès) sur la base de l'interprétation des diagraphies et des corrélations stratigraphiques des puits. Dans un deuxième temps, un modèle géologique 3D a été construit en utilisant les horizons de l'interprétation sismique convertis en profondeur et remplis avec des environnements de dépôts en utilisant une approche stochastique. Dans un troisième temps, des analyses statistiques ont été réalisées pour extraire des cartes de favorabilité du modèle 3D pour chaque réservoir. Les cartes de favorabilité définissent la probabilité d'intercepter un faciès avec des propriétés réservoir. En outre, des cartes de profondeur, de température, d'épaisseur totale et nette ont été définies. Le workflow a été complété par des interprétations quantitatives (volume d'argile, porosité totale et effective) le long des lignes sismiques 2D (600 km sur les 1930 km). Ce travail se poursuivi en 2024-2025 pour l'ensemble de la région Centre-Val de Loire et Picardie dans le bassin parisien
Impact of transfer time on trends in nitrate concentrations in mainland France
No full textInternational audienceThe Water Framework Directive (WFD) and its daughter directive aim to reduce water pollution and improve groundwater quality, especially concerning nitrate levels. Although various measures have been put in place to address contamination, their effectiveness can differ due to complex interactions among farming practices, climate, and geological features.Nitrate in the unsaturated zone mainly come from the application of fertilizers and the breakdown of organic matter. Predicting how long it takes for nitrate to move from the surface to groundwater is challenging because of lag time.This study examines how to estimate nitrate transfer times through the unsaturated zone, using an analysis of dominant rock types and hydrogeological models at the level of groundwater bodies. This method is particularly helpful for assessing contamination without needing detailed data on agricultural practices. By simplifying the assessment process, this approach improves our ability to manage contamination risks
Climate-change-induced seismicity: The recent onset of seasonal microseismicity at the Grandes Jorasses, Mont Blanc Massif, France/Italy
No full textInternational audienceModeling studies indicate that the geosphere can dynamically respond to climate change, increasing geological and geomorphological hazards. One such hazard is climate-driven seismicity due to hydrological changes, though observational evidence supporting this phenomenon remains scarce. We present the first dataset linking climate-change-induced snow/glacier melt to increased seismic hazard. Using a template-matching-enhanced catalog (2006–2022), we analyze the ongoing Grandes Jorasses Earthquake Sequence (GJES, Mont Blanc Massif, France/Italy; ML≤3.1/MW≤2.9), which exhibits a sudden onset of strong annual periodicity in fall 2015. Our relocations identify seismicity along a major fault zone outcropping in the Mont Blanc Tunnel, where runoff and isotope data suggest that inflow is dominated by young surface meltwater. Modeling meltwater infiltration with a 1D-hydraulic diffusion constrained by the S2M meteorological snowpack model confirms that most of the GJES seismicity can be meltwater-induced. Additionally, our statistical analysis reveals a migratory seismicity component, hosting the largest events. While initially triggered by seasonal meltwater, this component expands primarily via a tectonic mechanism affected by aseismic slip. We attribute the onset of increased and periodic seismicity in 2015 to intensified climate-change-driven heat waves affecting the Mont Blanc Massif's high-altitude cryosphere. Retreating permafrost and glaciers alter meltwater-infiltration pathways, inducing pore-pressure changes that trigger seismicity in new source areas. During peak meltwater-driven seismicity, the seismic hazard levels can rise by two orders of magnitude compared to pre-2015 levels. Our findings suggest that climate change can significantly elevate the local seismic hazard in alpine regions. This phenomenon may affect other glaciated areas globally, highlighting the need for improved seismic risk assessment for impacted alpine communitie
From oceanic to continental subduction and collision in the Western Alps: P-T-time evolution of the Briançonnais/Liguro-Piemont plate contact
No full textInternational audienceUnderstanding the evolution of convergent plate boundaries and the mechanisms of strain accommodation through time and space is made possible by studying exhumed subduction complexes within orogenic belts. This study uses the internal zones of the Western Alps, one of the largest and best-preserved fossil subduction complexes in the world, to track the transition from subduction to collision. We herein combine in-situ Ar-Ar and Rb-Sr data on white micas with pressure-temperature estimates derived from pseudosection modeling and Raman thermometry on carbonaceous material, along eleven transects crossing the mountain belt.Results (i) confirm the preservation of similar peak pressure-temperature conditions on both sides of the Briançonnais/Liguro-Piemont contact (as proposed by Mendes et al., 2023), (ii) indicate that the Briançonnais cover units reached their metamorphic peak around 50 ± 5 Ma and likely correspond to the former cover of the Dora-Maira massif, (iii) document the progressive slicing of large basement units at the end of the subduction process and the evolution of deformation (from localized at interface-scale to distributed at crustal-scale), and (iv) allow refining the initial structure of the continental margin and its role during convergence.This study also highlights the merits and limitations of Ar-Ar and Rb-Sr radiochronological systems, and in particular the complexity of the record associated with multiple metamorphic recrystallizations. Although the variable and in places marginal extent of excess argon complicates the interpretation of Ar-Ar ages, this study shows that the Ar-Ar system is likely more robust than the Rb-Sr system for tracking recrystallization history. The latter system appears sensitive to late re-equilibration episodes, potentially linked to fluid circulation.Mendes, K., Agard, P., Plunder, A., Herviou, C., 2023. Lithospheric-scale dynamics during continental subduction: Evidence from a frozen-in plate interface. Geology 51, 1153–1157. https://doi.org/10.1130/G51480
A Century of O&G Exploration in France: What Is the Legacy for the Energy Transition?
No full textInternational audienceThe global shift towards sustainable energy solutions has sparked renewed interest in subsurface exploration, driven by the urgent need for cleaner energy resources and carbon management strategies. In this context, France’s extensive history of oil and gas (O&G) exploration offers an invaluable foundation for transitioning towards low-carbon energy systems. Over a century of petroleum exploration has generated vast datasets, advanced technologies, and a culture of subsurface innovation that now holds transformative potential for geothermal energy, CO₂ storage, and hydrogen exploration.This study examines the legacy of O&G exploration in France and its role in the energy transition. It highlights how historical exploration data and scientific advancements are being repurposed for new applications, while also addressing the inherent limitations and challenges of reusing legacy datasets for modern energy exploration. Through case studies of ongoing research and collaborative projects, the analysis illustrates how France is leveraging its past to navigate a more sustainable and resilient energy future
A qualitative framework to identify variables influencing ecological sustainability in tropical small-scale agriculture
No full textInternational audienceSmall-scale agriculture continues to be the sector with the largest number of food-producing farms worldwide. According to literature, this sector is highly diverse, not highly mechanized, and has low environmental impact. As a result, smallholders play a crucial role in ensuring food security and sustainability. Despite their small scale, these systems must be evaluated and compared based on a wide variety of factors influenced by their specific contexts. Environmental conditions, personal preferences, economic constraints, government regulations, and social norms all contribute to these contexts. A comparison of the ecological sustainability of agricultural systems has shown potential, but is often hindered by substantial limitations. Many of these approaches fail to engage stakeholders comprehensively and elucidate the intricate structures, components, and feedback mechanisms of agricultural ecosystems. Incomplete portrayals of these systems' complex interdependencies lead to inaccurate sustainability assessments. A novel method for analyzing and comparing the ecological sustainability of small farming systems in the tropics is presented using semi-structured interviews, content analysis, and causal loop diagrams. Using interviews, we identified key drivers and challenges in the development of these systems. Through causal loop diagrams, we visualized each system and identified its feedback loops. Several important conclusions have been drawn from the study of these systems in Mariato, Panama:1.Ecological sustainability is driven by production, regenerative practices, and soil quality2.Subsistence and respect for nature motivated the farmers3.Degradation of soil and extreme dry seasons were major challenges4.All three system types that were compared tended towards equilibriu
Biotechnology for the Management of Mining Waste
No full textInternational audienceSince the 1980’s, BRGM has worked on the development and application of ecotechnologies for mining and mining environments. A particular focus has been on the application of biotechnologies to mining wastes and effluents. In the 1990s BRGM led the development of a commercial bioleaching process to recover cobalt from the tailings from a former copper mine in Uganda. After 10 years of R&D, the plant was constructed and reprocessed the target stock of tailings on site. Beyond the commercial success of this process, it had the added benefit of reducing acid mine drainage (AMD) generating on site; an excellent example of a win-win scenario. As such, bioleaching can be seen as a process to “depollute” environmentally dangerous sulfidic mining wastes. However, where the intrinsic metal content of such waste is insufficient, the process may be – in a strict sense – uneconomic.At the same time, the pace of technological development means that most electrical and electronic equipment becomes obsolete within a matter of years, resulting in the generation of vast quantities of electronic waste (e-waste). Where this cannot be recycled, it must be discarded. The CEReS concept, co-developed by BRGM, is a co-processing approach for both waste streams to produce metals and other valuable products, and to reduce or eliminate their environmental impact. This brings together two waste streams from opposite ends of the supply chain: turning each into a novel resource in a single, coherent ‘grave-to-cradle’ process. Where mine wastes cannot be reprocessed, they must be managed and stabilised as part of the long-term site management plan. Assisted phytostabilisation is often proposed as a suitable method to decrease erosion and thus risks associated with polluted particles that can be ingested or inhaled. However, one drawback of phytomanagement strategies is the production of vegetal biomass potentially containing high concentrations of toxic metals and metalloids. Furthermore, residual AMD may still occur onsite – either from the managed dumps or via internal voids etc – which requires treatment before discharge. BRGM has demonstrated the technical feasibility of using phytostabilisation biomass as a feed for semi-passive BSR (biological sulfate reduction) bioremediation of AMD. Therefore, biotechnologies can play a key role a holistic approach to the management of mining environments, through valorisation of residual metals and other products and the long-term stabilisation of final wastes and effluents
Flamborough head’s Upper Cretaceous Chalk: insights into a mixed deep-sea sedimentation system
No full textInternational audienceThe outcrops of the Flamborough Head promontory in Yorkshire, UK, including sea cliffs and inland quarries, provide an exceptional view of the Upper Cretaceous sedimentation. These exposures reveal chalks uplifted during the Tertiary inversion. A detailed sedimentological study of the Turonian to Campanian sections, incorporating both macroscopic and microscopic observations, reveals well-preserved sedimentary features consistent with depositional processes in a deep marine environment. The study identified three main types of facies: contourites, turbidites, and hemipelagites. Contourites, influenced by bottom currents, are composed of fine-grained chalk and exhibit thinly laminated beds with planar and undulating laminations, as well as current ripples. These beds, which can reach a total thickness of several dozen meters, exhibit internal organization with topographic compensation. That suggests deposition within larger contourite drifts -as observed in nearby offshore seismic profiles. Turbidites are characterized by massive beds with sharp bases fining upward, laminated deposits, and minimal bioturbation. Hemipelagites, in contrast, are intensely bioturbated mudstones with sparse fauna and show no evidence of current reworking. These deposits in Flamborough Head provides a valuable analogue for the North Sea deposits, offering insights into the dynamics of chalk deposition along the paleo-slope influenced by bottom currents. The identification of these contouritic facies in chalk across the Flamborough Head promontory highlights periods of increased bottom current activity, with hemipelagite-dominated intervals in between. The outcrop presents a unique combination of stylolitization from burial diagenesis and differential weathering, which highlight its sedimentary features. This provides insights into sedimentary processes that are usually hardly observable in chalk from cores. Although contourites geometries are widely reported through seismic data, facies observations are rare. This study not only provides a valuable analogue for North Sea Chalk deposits but also enhances our understanding of the sedimentology and current dynamics within the Chalk bassin
Tour d'horizon d'efforts pour le partage FAIR de Vocabulaires Européens pour le sol venant de projets EU Soil Mission
No full textInternational audienceVocabularies or thesauri, lists of terms with their definitions and unique ID, like a dictionary of alanguage, play a critical role in the domain of soil science, providing a standardized frameworkfor accurately documenting and communicating soil characteristics. In soil science, the use ofprecise and consistent terminology ensures the effective exchange of data, promotinginteroperability among researchers, practitioners, and decision-makers. A well-structuredvocabulary, part of soil classification or soil description standards, facilitates the classificationof soil properties, such as texture, structure, fertility, and organic content, allowing combiningdata from different sources but described in a similar way. And thereby enabling reliablecomparison and interpretation across different regions and time periods. Furthermore, thesevocabularies enable and support the development of standardized databases, soil datasets andsoil monitoring systems, which are essential for environmental management, land use planning,and agricultural practices. Inaccurate or ambiguous soil descriptions can lead to misinformeddecisions, making the establishment of clear, universally accepted vocabularies crucial foradvancing soil science, conservation efforts, and sustainable land management practices. Suchpractices would greatly enhance the FAIRness of the data being managed, ensuring dataconservation over time.Soil vocabularies come from many sources, some national or regional, some from internationalorganizations such as the Food and Agriculture Organization of the United Nations (FAO) or theInternational Union of Soil Sciences (IUSS), e.g. World Reference Base for Soil Resources (WRB)or FAO Guidelines on Soil Description. Several initiatives worked on the identification andprovision of agreed vocabularies in order to ensure the interoperability of their results at differentscales (national, EU, international). This includes work by standard setting organizations (eg. ISOTC190), legislation (eg. EU INSPIRE Directive) and of course numerous collaborative projects,such as SIEUSOIL, EJP SOIL, ISLANDR, SoilWise, SPADES, Soil Mission Support and MARVIC. Atpresent, many existing vocabularies have not been exposed in a referenceable and machine-readable manner, and instead remain “trapped” within PDF documents. Extracting the relevantconcepts and exposing them in both human and machine readable forms on persistent URIswould be a valuable step towards soil data harmonization.The European Mission: A Soil Deal for Europe, with currently about 50 research projects and anetwork of 100 living-labs and lighthouses, offers an interesting environment and opportunity forthe co-creation of a harmonised framework for soil vocabulary description. Due to the diversityof Soil Mission Projects, gaps in existing vocabularies can be identified and experience can begained in how to best present vocabularies for both data annotation as well as data discovery.In this presentation we will share the current status on this topic, offering a non-exhaustive yethopefully informative overview on existing materials (vocabularies and associated technologiesto share them), on-going work and key challenges for achieving better soil data interoperability.This study was made possible through funding from the EU's Horizon Europe program,specifically the ISLANDR and SoilWise project