Speaker(s): Guillaume Caumon

Date: Thursday 18th June 2020 – 11:00 am

Abstract:

In this talk, I briefly review some key machine learning principles and report on some recent work using convolutional networks for the structural interpretation of seismic images.

Speaker(s): Capucine Legentil

Date: Thursday 11th June 2020 – 11:00 am

Abstract:

This seminar is the occasion to present my PhD work on a method to robustly introduce boundaries in a triangulated geomodel, that allows the integration of new data, simulation results or geometry perturbation to reflect the subsurface uncertainties. The 2D geological model is locally updated, meaning that only a given region is modified and that the rest of the model remains identical. The area that can be modified is either specified as an input parameter or defined automatically. The input data is a triangulated surface storing the geological structure and physical properties. I will focus on the insertion of a horizon implicitly defined by an iso-value of a scalar field. The output is an updated mesh, which contains the new horizon. Distinctly from current model modification, the modifications are made to the mesh and aim to keep it valid throughout the transformations. The representation of geological structures as well as the computational support (mesh) can impact physical simulations. Once the local remeshing has been made, the impact of these updates on the model's physical behavior is evaluated thanks to the comparison of wave propagation profiles. These profiles are simulated using a Discontinuous Galerkin method.

Speaker(s): Marcus Apel

Date: Thursday 04th June 2020 – 2 :00 pm

Abstract:

In the Spring of 2018, a group of leading oil and gas companies met to discuss how contemporary cloud technology could be used to transform the current complex data and application environment. The Open Subsurface Data Universe™ (OSDU) Forum, a Forum of The Open Group, was created with the objective of enabling new cloud-native data-driven applications with seamless access to the full range of subsurface and wells data as well as supporting existing applications and data frameworks. The core principle of the OSDU solution is to separate data from applications. This will be achieved by developing a common data platform with standard public APIs and to involve global cloud hosting vendors to build working implementations. The focus of this presentation will be on data models and data architecture for geomodelling.

Speaker(s): Antoine Mazuyer

Date: Thursday 13th May 2020 - 11:00 am

Abstract:

Geological sequestration of CO2 in large quantity is one of the most promising methods to curb global warming. To achieve this goal, large volumes of CO2 have to be permanently stored in geological reservoirs. Modeling and simulating CO2 sequestration is a multi-disciplinary effort involving a large spectrum of physical and chemical phenomena. We focus this work on the generation of 3D structural models and meshes to support coupled numerical simulations with flow and poromechanical equations. Building such models and meshes is challenging as the poromechanical changes to stresses and strains are not limited to reservoir layers where CO2 is stored, but also in the surrounding formations (overburden, underburden, sides). Modeling surrounding rock formations is necessary to capture fault reactivation, uplifting and caprock failure issues during the injection. In this work, we propose guidelines to build such models using implicit and explicit modeling strategies and meshes. This work is supported by real field data from a depleted gas field in the Gulf of Mexico state water. This field is considered as a faithful analog to CO2 sequestration reservoirs in the regional Miocene sands.

Speaker(s): Bruno Levy

Date: Wednesday 06th May 2020 - 2:00 pm

Abstract:

There is a lot of scientific activity around Optimal Transport (OT for short), that has became a "buzzword". OT is at the connection between math, physics and computer science. It has also some interesting applications in AI, which attracted even more attention to it. In this presentation, I will take a completely different path: I will introduce OT with a physicist's hat on my head: My goal is to give an intuitive idea of OT, and its connections with physics. In particular, OT can be used as a component of a new class of numerical simulation methods, with interesting properties. In particular, it is possible to design a king of "moving mesh method" while exactly controlling the volume of the mesh elements. This can be used to simulate fluids, or to solve some inverse problems in astrophysics.

Speaker(s): Francois Bonneau

Date: Thursday 09th April 2020 - 4:00 pm

Abstract:

In this presentation, I will present the current state of my thoughts and developments related to stochastic Discrete Fracture Network simulations.

 

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Speaker(s): Guillaume Caumon

Date: Thursday 2nd April 2020 - 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

Date: Thursday 26th March 2020 - 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 

Date: Thursday 12th March 2020 - 1:00 pm

Location: Meeting room, ENSG Bat E, Nancy.

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

Date: Thursday 27th February 2020 - 1:00 pm

Location: Room G201, ENSG Bat G, Nancy.

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

Date: Wendnesday 19th February 2020 - 1:00 pm

Location: Meeting room, ENSG Bat E, Nancy.

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

Date: Thursday 13th February 2020 - 1:00 pm

Location: Room G201, ENSG Bat G, Nancy.

Abstract:

Bibliographic seminar presenting different karstic network skeleton simulation methods.

Speaker(s): DU KOU

Date: Thursday 06th February 2020 - 1:00 pm

Location: Meeting room, ENSG Bat E, Nancy.

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 January 2020 - 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).