Speaker(s): Guillaume Caumon

Location: Nancy.
 
Date: Thursday 2nd of April 4:00 pm.
 
Abstract:
 
Loop is a collaborative project dedicated to the development of an open source platform for modeling of highly deformed geological terrains and inversion. In this seminar, I will make a brief summary of the main advances shared by the 2020 Loop meeting participants in Western Australia. Themes include the overall project architecture, map and model validation, modeling, joint geophysical inversion.
Speaker(s): Corentin Gouache

Location: Nancy.

Date: Thursday 26th of March 2:00 pm.

Abstract:
 
Earthquakes occur everywhere and everytime. Moreover, large earthquakes that really impact our society are sparse events. That's why statistical analysis of seismicity attended to describe the large amount of small earthquakes in order to extrapolate to the large earthquakes through scaling laws. Thus, it has been found that independent seismicity uses to follow a Poissonian law whereas the dependant events follow a time-reversal law. However, these laws have been described in California or Japan, where seismicity is strong. Regarding the low amount of data in low seismicity areas like French mainland, the adequacy of these laws can be questioned. This seminar highlights the drawbacks brought by a classical model of seismic hazard estimation when applied on low seismic activity areas. A scheme is proposed to overcome these issues.
Speaker(s): Luc Scholtes

Location: Meeting room, ENSG Bat E, Nancy.
 
Date: Thursday 12th of March.

Abstract:
 
Predicting the strength of shale rocks is a basic but nonetheless critical requirement when designing CO2 or nuclear wastes storages. Even though geologic structures need to be considered above the meter scale when evaluating the strength of such systems, the intact rock behavior has to be thoroughly characterized before any further analysis. A particular feature of shale rocks is that they present highly nonlinear failure envelopes. Interestingly, despite this unanimously observed behavior, the linear Mohr-Coulomb criterion is still widely used in engineering practice (see for instance the petroleum or reservoir geomechanics taught in university courses). Of course, non linear strength criteria exist and should thus be considered more systematically when dealing with shale rocks (see for instance the criterion proposed by Singh). Nonetheless, as practical as they are for assessing the integrity of geologic materials, these formulations (empirical for the most of them) do not explain the underlying mechanisms involved in the failure processes. As a matter of fact, shale rocks present anisotropic structures, characterized by laminations, parallel layering or bedding features. These fabric properties induce a strong anisotropic behavior which directly controls the strength of shale rocks. It is thus crucial to consider such characteristics to better understand the associated failure mechanisms. In this work, we describe the dependency of Tournemire shale strength on the orientation of the loading relative to the bedding over a large range of confining pressures (from 2 to 80 MPa) based on a comprehensive series of experimental tests. Then, we assess the relevance of two practical empirical failure criteria to describe Tournemire shale strength. Finally, we simulate the triaxial tests performed on Tournemire shale using a specifically developed anisotropic discrete element model to get further insights into the mechanisms controlling its strength.
Speaker(s): Zoé Renat

Location: Room G201, ENSG Bat G, Nancy.
 
Date: Thursday 27th of February, 1:00 pm
 
Abstract:
 
Microseismic events are earthquakes of weak intensity and are difficult to locate with traditional methods. In the presentation, I will present some methods based on backward propagation of seismic recordings : time reversal method & reverse time modeling.
Speaker(s): Khalifa Eldursi
 
Location: Meeting room, ENSG Bat E, Nancy.
 
Date: Wendnesday 19th of February, 1:00 pm
 
Abstract:
 
Canada’s uranium production, currently ranked second worldwide and accounting for 17% of the world’s total, is entirely from the Athabasca Basin in northern Saskatchewan. The unconformity-related uranium deposits associated with this basin are among the highest-grade and largest uranium deposits in the world. Many of these deposits were discovered based on an empirical model that uranium mineralization took place near faults crosscutting the sub-Athabasca unconformity, where uranium-bearing oxidizing fluids met and reacted with reducing agents (i.e., graphite and hydrocarbons derived from, as well as ferrous iron-rich lithologies) and precipitated uranium ores. However, after more than 40 years of intensive exploration, this model is facing more and more challenges, and a better understanding of the factors controlling mineralization is needed.
Speaker(s): Yves Frantz

Location: Room G201, ENSG Bat G, Nancy.
 
Date: Thursday 13th of February, 1:00 pm
 
Abstract:
 
Bibliographic seminar presenting different karstic network skeleton simulation methods.
Speaker(s): DU KOU
 
Location: Meeting room, ENSG Bat E, Nancy.
 
Date: Thursday 06th of February, 1:00 pm
 
Abstract:
 
One of the most important subjects in mechanics of materials is to describe the macroscopic behaviours by considering the evolution of the complex microstructures and matrix anisotropy. It is especially for the porous composite geomaterials relating to the propagation of the micro-cracks and the growth of the micro-voids, which enormously affect their damage process. In our work, we are firstly interested in the microporoelastic modelling in order to estimate the effective properties of the studied geomaterials by taking into account the microstructure and matrix anisotropy. It is actually important for the derivation of micromechanical damage models that will be next realized in order to carry out the phase field modeling in the second part of this thesis.
Speaker(s): Capucine Legentil
 
Date: Thursday 23rd of January, 1:00 pm
 
Location: Room G201, ENSG Bat G, Nancy
 
Abstract:
 
Ce séminaire sera l'occasion de faire découvrir aux 3As l'IAMG (International Association for Mathematical Geosciences) et son Student Chapter. L'IAMG est l'association scientifique la plus proche des thématiques de recherche de l'équipe, et possède un Student Chapter à Nancy, qui est géré par les doctorants de l'équipe.
Le bureau de cette année est composé des doctorants de 1ère et 2ème année (Capucine Legentil, Zoé Renat et Paul Baville).
Speaker(s): Farah Al Sahyouni

Date: Thursday 16th of January, 1:00 pm
 
Location: Meeting room, ENSG Bat E, Nancy
 
Abstract:
 
Storage in salt caverns is currently the most efficient method for large scale storage of hydrogen. The Reservoir capacity, but mainly its sealing integrity (k <2 * 10-21 m2, in undisturbed areas) are the main reasons. However, if the deviatoric stress crosses the dilatancy boundary, it resolves the deformations in the pore structure and increases the permeability. Thus, the risk of leakage increases. Our goal is to study the change of the hydraulic and mechanical properties according to the damage. Several experimental techniques were used to characterize the changes in the properties of the samples before and after the mechanical tests, on cylindrical salt cores respecting the REV. The evolution of permeability as a function of the stresses is imposed by the modifications of the rheological behavior of the salt. It follows a percolation curve and the breakthrough point is at the dilatancy boundary. The hardening stage allows a reduction of the permeability.