A seminar by Bruno Lévy (INRIA) at ENSG, Nancy, room G201.
On Friday 19th of January, 1:00 pm.
Graphite is an open-source research platform for computer graphics, 3D modeling and numerical geometry. It offers an experimental 3D modeler, built in top of the Geogram programming library. This seminary is the occasion to present the last developments of the library and to introduce to the programming of GUI using Graphite.
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A seminar by Pauline Collon at ENSG, Nancy, room G201
On Friday 17th of November, 1:00 pm.
Ce séminaire sera l'occasion de vous présenter le système karstique de Furfooz (région de Dinant, Belgique) sur lequel Lorraine Dewaide, que je co-encadre, effectue sa thèse à l'Université de Namur. Dans ce système, développé dans les mudmounds Waulsortiens, différentes investigations de terrain ont été réalisées afin d'en comprendre le fonctionnement. Parmi celles-ci, plusieurs essais de traçage ont été caractérisés par l'apparition d'un "double-pic" assorti d'une "traînée". Plusieurs interprétations sont possibles pour expliquer ce double-pic. Pour mieux comprendre les phénomènes potentiellement en jeu, un analogue expérimental a été réalisé. En parallèle, un code numérique a été développé pour simuler le transport 1D de soluté dans des "conduits" parallèles échangeant entre eux.
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A seminar by Guillaume Caumon at ENSG, Nancy, room G201.
On Friday 15th of December, 1:00 pm.
Ce séminaire sera l'occasion de faire découvrir aux 3A comment la recherche s'organise au sein de l'équipe, quels sont les différentes entités qui interviennent, bref tout ce qui participe au fonctionnement du labo.
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A seminar by Nicolas Mastio at ENSG, Nancy, room G201
On Friday 10th of November, 1:00 pm.
A geomechanical model is usually contained inside a rectangular box shape. Displacements on the edges are fixed in some direction in order to impose the model to keep his shape. This kind of boundary conditions are called Dirichlet boundary conditions. Nevertheless, this kind of boundary conditions create boundary effects. Rather than imposing the ground to be contained in a rectangular box, a geomechanical model could be better represented by a semi infinite volume. Such a representation obviously cannot be solved by the finite element method, but Neumann boundary conditions can be found in the rectangular box which mimic the semi infinite extention of the model.
I will present the bibliography and the method I intend to use and I hope to present the results at the end of the year.
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A seminar by Marion Parquer at ENSG, Nancy, room G201
On Friday 8 of December, 1:00 pm.
Abandoned meander loops during the channel evolution are valuable witnesses of the paleo-trajectories of the system. The reconstruction of the complete history of the main channel is crucial for the understanding of ancient or modern channelized systems.
However, such information can be lost after the reworking of the channel belt through migration or avulsion processes after the loop cutoff. Moreover, deep structures can be difficult to observe on seismic images.
To overcome these difficulties, we propose to stochastically simulate meander loops inside the meander belt. This simulation is done for a given time step with constraints on the position, orientation and dimensions of the abandoned loop in order to fit the meandering context.
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A seminar by Antoine Mazuyer at ENSG, Nancy, room G201
On Friday 13 of Octobre, 1:00 pm.
Estimating the stress in reservoirs and their surroundings prior to the production is a key issue for reservoir management planning. In this study, we propose an integrated inverse method to estimate such initial stress state. The 3D stress state is constructed with the displacement-based finite element method assuming linear isotropic elasticity and small perturbations in the current geometry of the geological structures. The Neumann boundary conditions are defined as piecewise linear functions of depth. The discontinuous functions are determined with the CMA-ES (Covariance Matrix Adaptation Evolution Strategy) optimization algorithm to fit wellbore stress data deduced from leak-off tests and breakouts. The disregard of the geological history and the simplified rheological assumptions means that only the stress field, statically admissible and matching the wellbore data should be exploited. The spatial domain of validity of this statement is assessed by comparing the stress estimations for a synthetic folded structure of finite amplitude with a history constructed assuming a viscous response.
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A seminar by Modeste Irakarama, Gautier Laurent and Julien Renaudeau at ENSG, Nancy, room G201
On Friday 1st of December, 1:00 pm.
We introduce a new method for implicit structural modeling. The method exploits the highly symmetric nature of the Cartesian grid to implement efficient finite difference operators. The proposed method has the advantage of being much more simple to implement, and arguably numerically more efficient, than existing methods.
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A seminar by Pierre Martz at ENSG, Nancy, room G201
On Friday 23d of June, 1:00 pm.
Multiple ages from uranium oxides spanning over more than 1 Ga have been proposed as markers of several U-mineralizing events in the Athabasca basin (Saskatchewan, Canada) but the understanding of the nature and significance of the potential distinct U-mineralizing events is difficult. To unravel this potential complex sequence of fluid-flow events and to assess the importance of each events in the formation and evolution of the deposit as it is currently depicted, an integrated and systematic study has been carried out in 2D by coupling mineralogy, in situ U-Pb dating, and trace element geochemistry of UO2 from samples coming from two crossections crosscutting the Cigar Lake orebody, a world-class sandstone-hosted archetype of unconformity-related U deposit. This study shows that a first and major event of U deposition occurred at ~1430 followed by one poorly constrained non mineralizing major brecciation event occurring between 1000 and 700 Ma and three much younger events of U remobilization and deposition at ~340, ~225, and ~205 Ma. Each mineralization stage is characterized by a specific fingerprint including distinct mineralogical associations and geochemical signatures in trace elements. Using geochemical data from drillholes, a 3D scale modelization has been built showing the spatial repartition of the distinct U oxide types. It reveals that the U stock of the deposit was deposited during the first mineralizing stage, currently preserved in the core of the deposit, right at the unconformity and along the E-W shear structurally controlling the deposit. However younger fluid flow events have greatly remobilized the primary U stock so that the present mineable volume is now in fact formed by young mineralization (<350 Ma).
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A seminar by Agathe Carbonie at ENSG, Nancy, room G201
On Friday 24th of November, 1:00 pm.
Geological structural models (geomodels) representing the subsurface, individualize structures such as rock units or fault compartments.
In order to use these models for mesh based numerical simulations, their meshes must integrate these structures. Indeed, it allows to store consistent physical properties in each compartments and differentiate locally the rock mechanical properties.
We propose a method to update a geomodel by cutting its mesh elements. We implemented for this a version of the marching tetrahedra algorithm that keeps the mesh tetrahedral. This work has been developed with an implicit modeling framework where geological objects are represented as iso-values of a 3D scalar
field. Therefore, expliciting iso-surfaces within an implicit geological model can be useful for visualization and giving a boundary representation to the model.
The method starts with a purely tetrahedral mesh model. The mesh elements are first cut by an iso-value of an implicit property. Then the geomodel is updated, replacing the cut components by the individualized ones.
This work opens new perspectives for automatic mesh simplification and for incremental structural modeling. The module has been implemented in SCAR library using RINGMesh geomodels.
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