Speaker(s): Corentin Gouache

Date: Thursday 21st of June 2018

Location: room G201, ENSG, Nancy

Abstract:

Les modèles de prédiction de sismicité passent par une phase de caractérisation de la sismicité passée sur le territoire étudié. Cette caractérisation se fait, entre autres, via l’analyse des catalogues d’événements sismiques : liste des séismes et de leurs paramètres (localisation, temps d’occurrence, profondeur, magnitude) enregistrés par les observatoires. Dans le cadre d’une analyse de ces données par machine learning, plus ces bases de données sont « propres » et conséquentes, mieux c’est. Je m’attèle donc à rassembler la sismicité de toute l’Europe de l’Ouest tout en repérant et supprimant les doublons entre les différents catalogues nationaux. Ces doublons me servent à former des lois de conversion entre les magnitudes des catalogues (M, ML, Ms, Md, Mb …) et la magnitude de référence (seule magnitude présente dans le catalogue final) : Mw. A termes, les séismes étrangers (dans les pays voisins de la France) sont associés aux séismes français suivant leur localisation au sein de zone sismo-tectonique.

Speaker(s): Yves Frantz

Date: Friday 1st of June 2018

Location: room G201, ENSG, Nancy

Abstract:

Despite intensive explorations by speleologists, karstic systems remain only partially described as many conduits are not accessible to humans. Paleokarsts are buried karstic systems with a significant reservoir potential but they are not easily identifiable on seismic images, which leads to a huge uncertainty on the network location and the conduit geometry. Thus, it becomes necessary to resort to stochastic simulation to better assess that uncertainty, one of the main approach being to reproduce the topology and geometry information already observed on known networks.

During this seminar, I will mostly do a general presentation of karsts and present future work prospects.

Speaker(s): Melchior Schuh-Senlis

Date: Friday 25th of May 2018

Location: room G201, ENSG, Nancy

Abstract:

Le but est ici de présenter l'avancement actuel de mes recherches bibliographiques pour ma thèse, et les implications des différentes informations que j'ai réunies sur le reste de ma thèse. Ce séminaire a également pour but de discuter des différentes méthodes pouvant être utilisées et des différents moyens de les approcher durant ma thèse. Je parlerais pour cela de mes recherches sur les méthodes ALE (Arbitrary Lagrangian Eulerian) et PIC (Particle-In-Cell), sur leur utilisation actuelle sur des problématiques de tectonique salifère, et sur la possibilité de les adapter pour faire de la modélisation de failles et de la restauration géomécanique de modèles géologiques.

Speaker(s): Antoine Mazuyer

Date: Friday 27th of April 2018

Location: room G201, ENSG, Nancy

Abstract:

In this seminar, I will talk about the usage of elasticity properties to model the mechanical behaviour of the faults. I will present some preliminar results on simple synthetic models in order to integrate this method in efficient inverse approaches.

Speaker(s): Margaux Raguenel

Date: Friday 20th of April 2018

Location: room G201, ENSG, Nancy

Abstract:

Understanding the physical processes occurring in a geothermal reservoir is a key point to make decisions about resources exploitation developments. In the frame of the GEOTREF project in Basse-Terre, Guadeloupe, data have been acquired and interpreted by geologists and geophysicists. Numerical models are now build to assess geological scenarios in accordance with the obtained data and determine potential areas of interest. In this seminar, I will present my work on these numerical models. First, models have been designed to evaluate the impact of several parameters on heat transfers and fluid flows. These parameters have been incorporated in models to determine the realism of different geological scenarios explaining the presence of heat in Bouillante. To go further in the representation of complex geological and physical models, a tool linking two specialized libraries has then been designed and tested on several applications. The last part of this presentation will be a brainstorming on the potential use of this new tool and its application to the reservoir of Basse-Terre.

Speaker(s): Modeste Irakarama

Date: Friday 13th of April 2018

Location: room G201, ENSG, Nancy

Abstract:

Seismic waveform inversion methods are techniques for quantitative subsurface imaging by fitting synthetic data to observed data. Waveform inversion has received a lot of attention over the last couple of decades, mainly due advances in high performance computing resources, among other things. In this seminar, I attempt to give a practical introduction to linearized and nonlinear waveform inversion. The word practical, here, is synonymous with "computer implementation". I focus on computer implementation, mostly, as the underlying theory can be found in many textbooks. Questions and comments are encouraged during and/or after the presentation.

 
Date: Friday 23rd of March 2018

Location: room G201, ENSG, Nancy
 
Abstract:
 
Les grilles sont sans doute une des manières les plus simples de représenter des données, ce qui permet notamment de les utiliser pour optimiser certains calculs scientifiques de manière très efficace. Je me propose donc de vous présenter certaines utilisations possibles de celles-ci, ainsi que l'implémentation de grilles cartésiennes que j'ai effectué dans le logiciel RINGMesh, et la bibliothèque d'algorithmes spécifiques associés RINGGrid que j'ai codée en prélude de ma thèse, pendant mon CDD au sein de l'équipe RING.
 
Date: Thursday 22nd of March 2018

Location: room G201, ENSG, Nancy
 
Abstract:
 
Hexahedral meshing of general domains is the ultimate challenge in mesh generation. The most promising methods are indirect, they combine the elements of a initial tetrahedral mesh to create prisms, pyramids and hexaedra. They build a mesh composed of a majority of hexahedra. In this talk, I wll present the main steps of indirect meshing, the latest results of our team and the remaining challenges to reach real time hex-dominant mesh generation.

Speaker(s): Pierre Anquez

Date: Friday 23rd of February 2018

Location: room G201, ENSG, Nancy

Abstract:

Meshing a 3D geological model is often essential in integrative subsurface modeling, but it is often a time-consuming task that typically requires a lot of user interaction. The difficulty is double: (i) the invalidity of the models and (ii) their geometrical complexity. The principal cause of invalidity for 2D or 3D boundary models is the non-watertightness. However, watertightness is generally required by meshing methods. In addition, the inherent geometrical complexity of geological models (due to e.g. thin layers, unconformities, or small fault displacements) strongly constrains the quality of the mesh to generate. To have a good mesh quality, one solution is to modify the geological model by merging locally or displacing its boundaries before generating the mesh.
In this seminar I will present a method I am currently developing to detect and fix geological model invalid and complex features. I model these features by a graph providing a formal framework to operate and correct the input model. The possible operations to fix the geometrical and topological issues are equivalent to graph elementary operations. This seminar will also be an opportunity to present the GJK algorithm, a fast algorithm to compute convex shape intersection and distance, I intend to use in geomodel invalid feature detection process.