Speaker: Laura Gaillard
Date: Thursday 20th of January 2022, 1:15 pm.
Abstract:
Le DIspositif de Modélisaton analogIque TRIaxial (DIMITRI) est une presse triaxiale d’un volume utile comprimé de 2 m3 au sein duquel des galeries peuvent être excavées. Il permet donc d’étudier le comportement mécanique de modèles réduits d’ouvrages souterrains. Dans le cadre de l’étude d’un modèle réduit d’une mine souterraine dans un massif rocheux fracturé, un système d’instrumentation du dispositif doit être développé. Le massif rocheux discontinu est représenté par un matériau analogue réalisé par impression 3D combinant sable et liant phénolique. L’objectif est de proposer des solutions techniques d’acquisition des déformations et des contraintes dans des zones localisées du modèle réduit. Ainsi, seront présentés les premiers procédés à l’étude pour cette instrumentation au cœur du massif.
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- Category: Seminar
Speaker: Nina Fermet-Quinet
Date: Thursday 25th of November 2021, 1:15 pm.
Abstract:
La Guyane est un territoire géo-écologique notamment caractérisée par la présence d’or primaire et secondaire. L’exploitation de cette ressource génère des impacts positifs (emplois directs, développement de l’activité locale…) et négatifs (destruction de la biodiversité, pollution…). Dans une précédente thèse, une méthodologie d’évaluation des risques positifsetnégatifs baséesur différents scénariosdedéveloppement minier a été testée et validée afin de pouvoir comparerdifférents scénariosà l’échelle duterritoire. L'objectif demathèse est de généraliser cette approche en considérant (i) d’autres événements générateurs que la rupture de digue minière ; (ii) des impacts ordinaires causés par l’activité normale des projets (iii) l’activité illégale sur le territoire. Suite à une première mission de terrain en Guyane, les observations et les données récoltées seront exposées afin de discuter des nouvelles perspectives de recherches quiy sont associées.
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- Category: Seminar
Speaker: Abdessamad Nait Ouhra
Date: Thursday 13th of January 2022, 1:15 pm.
Abstract:
The rheology and dynamics of red blood cells (RBCs) under confined flows, are studied in the Stokes limit. We numerically investigated the lateral migration of a suspended vesicle (a model of (RBCs)) in a bounded shear flow. We explore the relevant dimensionless parameters to study the dynamics and rheology of a vesicle as a function of the viscosity contrast λ = ηin/ηout, where ηin, ηout denote the inner and the outer viscosities. We found that the equilibrium lateral position of the vesicle exhibits a saddle-node bifurcation as a function of the bifurcation parameter λ, which leads to a surprising acute decrease of the effective viscosity of the suspension at a critical value of viscosity contrast (λc). We found that below a critical viscosity contrast λc, the vesicle is centered, and above λc, the vesicle can be either centered or off-center depending on initial condition. This study can be exploited in the problem of cell sorting out and can help understanding the rheology of confined suspensions.
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- Category: Seminar
Speaker: Narges Dashtbesh
Date: Thursday 18th of November 2021, 1:15 pm.
Abstract:
I will present in this seminar a sequential approach to accelerate immiscible multiphase flow modelling in heterogeneous porous media using discontinuous Galerkin methods and dynamic mesh coarsening. This approach involves dynamic domain decomposition and different solution strategies in the different flow regions, using a criterion that can be fastly evaluated. I will present a technique to estimate the position of the saturation front and identify the flow zones that need high-resolution gridding. The accuracy of the proposed approach is evaluated through test cases from the SPE10 model.
In the second part, I will briefly talk about my postdoc project on groundwater contaminations by nonaqueous phase liquids (NAPL), as part of the QUASPER project.
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- Category: Seminar
Speaker: Fabrice Taty-Moukati
Date: Thursday 6th of January 2022, 1:15 pm.
Abstract:
Building the data energy term of marked point processes is of an utmost importance. The main reason is that characterizing objects on images, in the framework of marked point processes, requires building a probability density, which is often composed of two terms. The first one is the interaction energy characterizing interactions between objects and the second one is the data energy which contains the locations as well as sufficient information of objects. The goal of our work is to detect and characterize seismic faults in the context of image analysis to deals with fault uncertainty problems. Seismic images themselves are subject to uncertainties, mainly due to processing steps as well as the limited seismic bandwidth. For these reasons, we cannot rely on a single interpretation to perform analyses of any field or reservoir, even if obtained with neural networks, since we know that this interpretation can comprise ambiguities. We also know that geological faults, as one may take a closer look at them, are not linear but damage areas composed of several small cracks. Based on the facts set out above, we adopt the foregoing approach based of segment processes to characterize and detect seismic faults. We do that since a seismic fault network can be seen as a realization of a marked point process. One of our goals is to increase the resolution of seismic faults that we seen in seismic images. For doing so, we start with fault probabilities provided by FaultNet3D [Wu et al.,2019] to better constrain the data energy term in accepting or rejecting segments.
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- Category: Seminar
Speaker: Enrico Scarpa
Date: Thursday 4th of November 2021, 1:15 pm.
Abstract:
Proper representation of connected features is crucial when modeling the fluid circulation in the subsurface. In that framework, connectivity metrics are essential tools to describe a reservoir and its hydrodynamic behavior. This seminar will briefly review the role of connectivity metrics developed for a channelized deep-water system. The discussed metrics cover static and dynamic points of view. The static connectivity metrics depend only on the parameter fields such as hydraulic conductivity or geological facies. Conversely, dynamic connectivity metrics are related to physical processes such as flow or transport. This talk wants to highlight the influences of the stacking pattern of channels and their impact on simple flow models. The purpose is to discuss the relations between the geological representation of connected components, connectivity measures, and the hydrodynamic behaviors of heterogeneous deposits.
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- Category: Seminar
Speaker: Vincent Bos
Date: Thursday 16th of December 2021, 1:15 pm.
Abstract:
La recherche développée dans le cadre d'un post-dotorat à l'Université de Lorraine - CNRS, UMR 73 59, au laboratoire GeoRessources (Mines, Nancy, Campus Artem) vise à analyser la transition énergétique au prisme de la ressource lithium en interrogeant le système de production mondialisé dans lequel elle s’inscrit et ses ancrages territoriaux. La géo-économie du lithium restructure les territoires et conditionne la vie sociale, en particulier dans les localités où la ressource est exploitée. Notre projet entend saisir les reconfigurations des réseaux de production globaux du lithium (GPN, Global Production Networks) en éclairant les stratégies de ses principaux acteurs (entreprises, Etats), dans les deux principaux espaces nodaux de sa chaîne extractive : l’Amérique latine (Argentine et Chili principalement) et l’Australie. Le focus sur les infrastructurures (énergétiques, productives, de transport) des projets lithinifère permettra d'analyser les formes de territorialisation locale des projets minéro-énergétiques au prismes des paysages des nouvelles géographies de l'énergie et des imaginaires que leurs promoteurs y associent. Le projet entend ainsi (re)connecter les relations, souvent invisibles, entre les espaces de production des ressources, les espaces de production des technologies de la transition énergétique, et les espaces de consommation des ressources semi transformées (dérivés) et des produits finis (batteries), dans le but d’éclairer les trajectoires locales, nationales, régionales et mondiales de l’économie du lithium, de la transition énergétique et du développement. Fondé sur une approche interdisciplinaire dans l’esprit du LabEx RESSOURCES21, ce projet s'inscrit dans les études en cours sur les activités extractives en articulant la géographie des gisements avec des approches en sciences humaines et sociales (géographie économique, géographie critique, anthropologie) et un dialogue avec les sciences s’intéressant aux ressources minérales, à leur exploitation et à leur transformation (géologie, métallurgie, hydrométallurgie).
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- Category: Seminar
Speaker: Ever-Dennys Coarita-Tintaya
Date: Thursday 28th of October 2021, 1:15 pm.
Abstract:
Context of this work is related to underground hydrogen storage in salt caverns. The operational phase (injecting and extracting, according to daily or seasonal cycles) can affect stability of the cavern and initiate development of fractured zones. This can modify the transport properties and therefore potentially cause hydrogen leakage problems around the cavern.
Based on the mechanical and hydromechanical behaviour of salt rock known from experimental data, as well as on the rheological models available for this material, we propose a model that considers the short-term and long-term behaviour of salt rock. In the short-term behaviour we have a macroscopic elastoplastic and damage constitutive model. In the long-term behaviour, the three creep types are considered: (i) transient (or primary) creep; (ii) steady-state (or stationary) creep; and (iii) acceleration (or tertiary) creep. Thus, this model describes the key mechanisms of salt rock behaviour.
To evaluate and validate the numerical implementation in Comsol Multiphysics®, triaxial tests were simulated and the results obtained correlate well with the theoretical criteria. The application of the proposed model was evaluated on salt caverns where hydromechanical simulations were carried out under saturated conditions. The analysed scenarios were shallow and very depth caverns, as well as seasonal and daily hydrogen operating cycles.
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- Category: Seminar
Speaker: Zoé Renat
Date: Thursday 2nd of December 2021, 1:15 pm.
Abstract:
The time-reversal method is based on the back-propagation of seismic waveforms recorded at a set of receivers which form a closed surface. When the elastic properties of the medium are correct, the seismic energy focuses at the source location, creating a focal spot. Such a spot is smooth in space, whereas the original wavefield is characterized by a displacement discontinuity at the source. The goal of the present work is to discuss the link between the focal spot and the original source using the concept of homogenized point-source recently proposed by Capdeville (2021). We show that the back-propagated wavefield is equivalent to the sum of two low-wavenumber fields resulting from the homogenization of the original point-source. In other words, the homogenized point-source is the equivalent force for producing the focal spot. In addition to the demonstration in the general
3D heterogeneous case, we present numerical examples in 2D including the case of an extended source made of multiple point-source.
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- Category: Seminar