Speaker: Ever Coarita
Date: Thursday 30th of March 2023, 1:15pm.
Abstract:
Les travaux portent sur l'analyse des cavités salines dans le contexte du stockage souterrain de l'hydrogène et de la transition vers les énergies renouvelables. Le sel gemme présente de bonnes caractéristiques hydromécaniques pour le stockage du gaz dans les cavités salines. Cependant, en raison de la demande, par exemple pour le chauffage en hiver, les cavités sont soumises au soutirage ou à l'injection de gaz. Ces opérations peuvent endommager la roche saline et, par conséquent, provoquer des fuites de gaz à travers la paroi de la caverne. L’exposé présentera les résultats de la modélisation hydromécanique des cavités salines soumises à des cycles d'exploitation saisonniers et journaliers, ainsi que les travaux de modélisation en cours.
- Details
- Category: Seminar
Speaker: Bérénice Vallier
Date: Monday 27th of March 2023, 2pm.
Abstract:
Many numerical models studying the natural hydro-thermal circulation and the impact of industrial exploitations have been developed over the past decades. However, numerical methods which integrates several multi-physical and multi-scale measurements are under-represented. In the first part of the research, a natural large-scale hydro-thermal circulation is studied using a simplified thermo-hydro-mechanical model. Key rock physics properties are inverted from observed temperature and stress-depth profiles. On the other hand, this model with a complex coupling does not incorporate the details of the fluid flow along the major faults. The study provides new insights on the extension of the hydro-thermal convection cells through depth and on the up-scaling of rock physics properties from laboratory scale to field scale. In the second part, the anthropogenic impact on a natural large-scale system is analyzed. The aim of the study is to simulate far-field pore pressure disturbances from fluid injection in fractured porous medium. Studying the diffusion of pressure disturbances will allow to understand the evolution of the effective stress and to quantify the triggered seismicity. A large-scale homogeneous porous medium as a fault structure is represented. The pressure disturbances’ distribution is investigated under different states: (i) controlled injection; (ii) injection/production system. The numerical pressure perturbations are in good agreement with the analytical results. To improve the current models, further work employing more realistic scenarios of fluid injection conditions are currently under investigation.
- Details
- Category: Seminar
Speaker: Paul Marchal
Date: Thursday 23rd of March 2023, 1:15pm.
Abstract:
When modelling hydrothermal deposits, it is critical to consider the interrelationship between fluid flows, tectonic structures, such as faults, and the initial petrophysical characteristics of the rocks. This is essential to improve current modelling processes, which are mainly based on classical deterministic interpolation methods, by incorporating geological knowledge within the modelling approach. This allows a better understanding of orebodies genetic processes and thus help the planning of exploration campaigns, as characterizing altered zone geometry is often a proxy for targeting ore zones in several types of deposits. It also improves the mineral resources of deposits evaluation for mining purposes. The key idea is to translate the hypothetical genetic link between faults, stratigraphic contacts, and fluid sources on the one hand, and the geometry & shape of altered rocks halos on the other, into the modelling approach. We choose to extend the skeleton-based approach, developed by [Henrion et al., 2010] who models karst conduits as an implicit distance function to a structural skeleton, which is perturbed by a data-constrained disturbance field, to incorporate and assess uncertainties. Moreover, based on the work of [Rongier et al., 2014], we wants to incorporate anisotropic behaviour of rocks by customizing this implicit distance field using petrophysical data, such as permeability. Then, given the sparse nature of drillholes datasets, we suggest that generating unknown structural elements between data is essential to better assess uncertainties related to halos’ shapes. This works develops these methodologies to model genetically–related concentric alteration & mineralization halos related to hydrothermal processes such as Unconformity-related uranium deposits of the Athabasca.
- Details
- Category: Seminar
Speaker: Boris Kratz
Date: Thursday 16th of March 2023, 1:15pm.
Abstract:
Les métropoles sont confrontées à une saturation de leurs axes de mobilité, ce qui a entraîné la mise en place de nouveaux grands projets d'infrastructures tels que la construction de tunnels. Cependant, la construction de tunnels comporte des risques, notamment les déplacements surfaciques causés par les travaux d'excavation. Pour évaluer ces risques et protéger les bâtiments situés à la surface, il est nécessaire de prédire et surveiller l'ampleur des tassements. Pour cela, différentes méthodes de prédiction ont été développées, allant des méthodes empiriques et analytiques aux méthodes numériques. Les modèles 3D par éléments finis (EF), avec des lois de comportements mécaniques des sols réalistes, sont considérés comme étant les plus prédictifs, mais sont complexes et coûteux en temps de calcul. Un méta-modèle, ou modèle de substitution, peut fournir une approximation suffisamment précise d'un modèle (EF), avec l'avantage d'être beaucoup moins coûteux en temps de calcul. Cette présentation vise à expliquer les étapes nécessaires pour développer un tel méta-modèle pour le problème de l'excavation par un tunnelier. En particulier, nous discuterons de la précision des méta-modèles en fonction du nombre de simulations effectuées pour la construction du méta-modèle.
- Details
- Category: Seminar
Speaker: Augustin Gouy
Date: Thursday 9th of March 2023, 1:15pm.
Abstract:
Karst systems, which are often present in carbonate rocks, are characterized by a complex ensemble of underground drains which strongly control the water flow in the massif. It is therefore necessary to take into account the karst network to model the hydrogeological functioning of karstified rocks. Information on the position and the geometry of those caves is however often scarce, indirect and imprecise. A discrete karst network simulation approach is proposed, capable of representing the diversity of possible models for a given dataset, while exploiting those data to reduce the ensemble distribution. This method solves a shortest path algorithm between sinks and springs –respectively the inlets and outlets of the network- with the use of an anisotropic cost function defined in the whole domain. The cost represents in a simplified way the physico-chemical processes of karstification, while facilitating control of the geometry and topology of the generated networks. Examples derived from a real case study show how the position, density, connectivity rules and hierarchy of the network’s inlets and outlets can be used to create realistic karst networks under various underlying hypotheses.
- Details
- Category: Seminar
Speaker: Paul Cupillard
Date: Thursday 2nd of March 2023, 1:15pm.
Abstract:
Tectonic processes and the industrial exploitation of the subsurface induce brittle deformations in the earth crust, leading to fractures at all scales. Geological observations have evidenced that a power law is appropriate to describe the density of a fracture set as a function of the fracture size. Nevertheless, for either theoretical or computational reasons, studies on seismic wave propagation in fractured media have been restricted to a short range of fracture sizes so far. In particular, effective medium theories all rely on an Elementary Representative Volume (ERV) consisting of a host matrix in which cracks are included. Assuming the ERV small with respect to the wavelength, then it is in a quasi-static regime of stress so that techniques from micromechanics can be used to compute an equivalent medium. In the frame of a 18-month post-doc, Anaïs Ibourichène started working on the application of the non-periodic homogenization method to fractured media to go beyond the ERV setting and explore the effect of a wide distribution of crack sizes on seismic wave propagation. I here present the preliminary results obtained by Anaïs in 2D. First, the effective properties computed using the homogenization in the case of Eshelby problems are compared to analytical solutions provided by various effective medium theories. Then, the homogenization is applied to a synthetic mass rock which contains different fracture sets, each set being characterized by a length l (up to λmin/4) and a density d ∼ l−3. Finally, some short-term and long-term perspectives of this work are discussed.
- Details
- Category: Seminar
Speaker: Amandine Fratani
Date: Thursday 23th of February 2023, 1:15pm.
Abstract:
The CO2 storage interests several industries to reduce their net carbone missions. Therefore, reservoir simulation methods need to be adapted to the injection of CO2, in particular on unstructured grids to allow a geomechanical coupling. For three years, TotalEnergies has been developing a workflow for fluid flow simulation on unstructured grids. This presentation focuses on the addition of analytical aquifer in the workflow. Analytical aquifers are one method used to consider the behaviour of water outside the reservoir. Several analytical aquifers can be implemented, we only focus on the implementation of radial analytical aquifers in a ParaView plugin. Faults were already implemented in the workflow, but some modifications on this part were performed in order to bring consistency between the different parts. Finally, two applications are proposed. The first is a synthetic oil production case, which showed that the workflow is working as expected. In this case, aquifer behaviour in presence of fault is checked and a sensitivity analysis of the Carter-Tracy parameters is made. Some additional work remains to obtain the same results between the various grid types. The second application is a CO2 injection in a ‘’real’’ model, showing interesting results not fully understood yet.
- Details
- Category: Seminar
Speaker: Danielle-Rita Pajiep-Ngongang
Date: Thursday 16th of February 2023, 1:15pm.
Abstract:
L’évaluation des risques liés à la présence d’ouvrages souterrains (carrières, mines, cavités naturelles) en cours d’exploitation et/ou abandonnés pose légitimement la question de la stabilité dans le temps de ces ouvrages. En janvier 1910 est survenu l’effondrement de la carrière souterraine dite « Beaulieu », située dans la commune de Château Landon (département de la Seine-et-Marne), après une série de précipitations et la forte crue du cours d’eau en pied de carrière. Avec le changement climatique et devant le risque de crues exceptionnelles et les conséquences possibles d'instabilités de ces ouvrages souterrains, l’Ineris a décidé d’approfondir les connaissances actuelles afin de pouvoir prédire l’ampleur et l’impact en surface de ces instabilités. Pour ce faire la carrière de craie « Royer » à Château Landon (77) a été sélectionnée car elle présente de fortes similitudes géologiques et géotechniques avec la carrière voisine Beaulieu qui s’est effondrée. Le comportement de cette craie a fait l’objet de plusieurs études expérimentales au sein de l’Ineris notamment dans la thèse de Lafrance (2016). Toutefois très peu de données ont pu être collectées en raison de sa forte sensibilité à l’eau. Les principaux objectifs de mes travaux visent donc à l’amélioration des connaissances du comportement hydromécanique de cette craie lorsqu’elle est soumise à des sollicitations hydromécaniques et au développement d’une approche de modélisation numérique pertinente pour l’analyse de la stabilité à long terme des cavités exposées à des conditions environnementales complexes.
- Details
- Category: Seminar
Speaker: Christophe Reype
Date: Thursday 9th of February 2023, 1:15pm.
Abstract:
The analysis of hydrogeochemical data aims to improve the understanding of mass transfer in the sub-surface and the Earth's crust. This work focuses on the study of fluid-fluid interactions through fluid mixing systems, and more particularly on the detection of the compositions of the mixing sources. The detection is done by means of a point process: the proposed model is unsupervised and applicable to multidimensional data. Physical knowledge of the mixtures and geological knowledge of the data are directly integrated into the probability density of a Gibbs point process, which distributes point patterns in the data space, called the Hug model. The detected sources form the point pattern that maximises the probability density of the Hug model. This probability density is known up to the normalisation constant. The knowledge related to the parameters of the model, either acquired experimentally or by using inference methods, is integrated in the method under the form of prior distributions. The configuration of the sources is obtained by a simulated annealing algorithm and Markov Chain Monte Carlo (MCMC) methods. The parameters of the model are estimated by an approximate Bayesian computation method (ABC). First, the model is applied to synthetic data, and then to real data. The parameters of the model are then estimated for a synthetic data set with known sources. Finally, the sensitivity of the model to data uncertainties, to parameters choices and to algorithms set-up is studied.
- Details
- Category: Seminar