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: 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: 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
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: 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: 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: 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: Capucine Legentil
Date: Thursday 21st of October 2021, 1:15 pm.
Abstract:
In this work, we present a local updating method to test different contact depth scenarios and assess their impact on wave propagation in the subsurface. We propose to locally modify a 2D geological model and run time-dependent elastic simulations. The input model triangulation is conforming to geological structures. The 2D meshed model is locally updated, which means that only the reservoir compartment is modified. Several model geometries are generated by inserting a new interface, in this paper a gas-water contact that is defined by a scalar field. We quantitatively evaluate the impact of the gas-water contact depth on elastic wave propagation. We run the numerical simulations with Hou10ni2D code, which is based on a Discontinuous Galerkin method. The simulation results are compared to a reference depth by computing the L2-norm at a set of seismic receivers. Results show a consistent behavior: we observe a positive correlation between the depth difference and global L2-norm for all receivers. This approach could therefore be integrated into an inversion loop to determine the position of the fluid contact and reduce uncertainties in the reservoir model from a few seismic sensors.
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- Category: Seminar
Speaker: Emilio Abi Aad
Date: Thursday 14th of October 2021, 1:15 pm.
Abstract:
L’objectif principal de cette thèse est de comprendre le comportement mécanique d’un massif rocheux soumis à des sollicitations mécaniques. Notre objectif à terme est de modéliser une exploitation minière creusée dans un massif rocheux discontinu, en utilisant une modélisation physique. Ce type de modélisation permet d’obtenir des résultats quantitatifs en complément de la modélisation numérique. Néanmoins, la transposition des résultats de l’échelle réduite à l’échelle du prototype nécessite de respecter les facteurs d’échelle.
L’originalité de ce travail consiste à développer une méthode innovante, basée sur les techniques d’impression 3D combinant du sable et un liant phénolique, pour introduire explicitement des joints rocheux à propriétés mécaniques et géométriques contrôlées. L’utilisation de cette technique peut permettre la réalisation de modèles réduits discontinus de géométrie très précise et reproductibles.
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- Category: Seminar