Speaker(s): Nicolas Clausolles

Date: Thursday 16^th of May 2019

Location: room G201, ENSG, Nancy

Abstract:

Salt welds are surfaces or zones resulting from the (nearly) removal of salt from an initial layer or diapir, putting in contact  originally separated sedimentary layers. They are still poorly known and few sudies and data are available in the scientific literature, although their impact on reservoir sealing is globally recognized.

This seminary is the occasion to present my recent works on the modeling of salt welds, starting from an initial implicit structural model where salt geobodies have already been interpreted. The first step consists in detecting the isolated salt volumes in the model that require to be connected. Then the weld surface is extracted from the scalar field defining the structural model using an image segmentation method, the watershed segmentation. This segmentation defines a semi-infinite plane through the model. This plane is finally truncated using some visibility criteria to obtain the final weld surface.

Speaker(s): {mattia martinelli}

Date: Thursday 7^th of March 2019

Location: room G201, ENSG, Nancy

Abstract:

Outcrop analogues have an important role in hydrocarbon exploration and reservoir characterization, because they can help filling the gap between seismic and borehole scale. In this seminary, I will present the results from our project in the Gozo Island (Maltese Archipelago). Here, a Late Oligocene-Early Messinian carbonatic sequence, composed by different types of carbonates, was affected by two main extensional tectonic : i) NW-SE extension during the Aquitanian ii) N-S extension from the Middle Miocene onward. These tectonic events instigated the formation of a complex fracture network, that was investigated using 3D Digital Outcrop Models (DOM) based on photogrammetric drone surveys, and extracted from key outcrops in different units. It allowed us to quantitatively characterize fracture parameters within different mechanic/stratigraphic facies. All this information were used to reconstruct the fracture pattern variability at the scale of the whole island. The next step of this work will be to realize a DFN model using the obtained fracture parameters.

Speaker(s): Melchior Schuh-senlis

Date: Tuesday 11^th of April 2019

Location: room G201, ENSG, Nancy

Abstract:

The Finite Element Method (FEM) is widely used to solve Partial Differential Equations. It relies on performing computation on a reference element and linking the results to the rest of the model through shape functions. Since multigrids have elements that are very similar to each other (different sizes of rectangles in 2D and hexaedron in 3D), applying the FEM on them simplifies the associated shape functions while reducing the computational cost compared to very fine regular grids. The aim of this seminar is to show how the deal.II library deals with this problem, especially the handling of hanging nodes, and the advancements I have made in using it for implementing mechanical simulations in the subsurface.

Speaker(s): Pierre Anquez

Date: Tuesday 21^st of February 2019

Location: room G201, ENSG, Nancy

Abstract:

In this work in collaboration with the MouvGS team of the CEREMA (Sophia-Antipolis), we study site effects in the lower Var valley near Nice. We propose to simulate plane wave propagation in a SW-NE cross-section using Discontinuous Galerkin FE solver. To do so, we need a triangular mesh of the cross-section. Due to tangential contacts and thin layers, the quality of the mesh is poor : some triangles are very flat leading us to decrease time discretization for the simulations. As a consequence, the computation time of simulations severely increases. A 6-second wave propagation simulation on this model takes us more than 18 days ! This is completely impractical.
In this seminar, I will show strategies of model simplifications, using manual and automatic methods, with the aim of decreasing the computation time. We propose different models and we make a comparison of simulations results using these models.

Speaker(s): {Radu Stoica}

Date: Thursday 11^th of April 2019

Location: room G201, ENSG, Nancy

Abstract:

Spatial data are sets of observations made of elements having two components. The first component gives the coordinates where the observation took place. The second component, represented usually by a multi-dimensional real vector, represents the measures associated at the corresponding location. Digital images, environmental data in epidemiology or catalogues of celestial bodies in astronomy are some typical examples of spatial data.
The spatial character of the data induces a strong morphological component to the possible answers that may be given to questions arising from the data analysis. This explains why the question almost always arising is what is the pattern hidden in the data ?
The main assumption of our work is that the pattern we are looking for is made of random objects that interact.
Marked point processes are a probabilistic tool able to model random configurations of interacting objects. The main difficulty with these models is that they do not always exhibit a precise analytical form for their normalising constants. Hence sampling from such a probability density requires adapted MCMC simulation. Within this framework, statistical inference can be done,using methods such as the simulated annealing algorithm, the Monte Carlo maximum likelihood, permutation tests and bootstrap methods.
The aim of this talk is to introduce marked point processes and to illustrate their applications with examples and data sets coming from : cosmology, image analysis and environmental sciences.

Speaker(s): Paul Baville

Date: Tuesday 14^th of February 2019

Location: room G201, ENSG, Nancy

Abstract:

Depuis près de 10 ans, une intense activité autour des corrélations automatiques de puits s'est mise en place. Ainsi, 2 thèses ont été menées par Florent Lallier (Corrélation de puits stochastique en 2012) et Jonathan Edwards (Gestion des incertitudes dans la corrélation stratigraphique de puits en 2017) au sein de l'équipe et un nouveau projet WeCo a vu le jour depuis environ 1 an. C'est à mon tour désormais et je voudrais vous présenter les différents outils utilisés et développés au labo que je vais utiliser pendant ma thèse.
Je vais d'abord faire un bref résumé de ce qu'on peut interpréter à partir de données de carottes et de logs pour obtenir des marqueurs sur chaque puits. Ensuite je vais vous présenter l’outil Dynamic Time Warping DWT et comment il est utilisé dans le processus de corrélation de puits. Et pour finir je vais vous parler de ce que je compte faire au début de ma thèse.

Speaker(s): {Jean-Marc Montel}

Date: Thursday 26^th of March 2019

Location: room G201, ENSG, Nancy

Abstract:

La statistique des semis de point (point processing) est un outil de statistique spatiale qui permet de caractériser la distribution des points sur une surface ou dans un espace. Il n'a jusqu'ici que très peu été utilisé en géosciences. Au cours de mon séminaire, je reviendrai sur les bases des semis de point puis j'expliquerai la démarche que je développe qui combine l'élaboration d'outils, le développement de simulations et la recherche d'objets géologiques pertinents. Je terminerai en montrant quelques exemples d'application.

Speaker(s): Guillaume Caumon

Date: Tuesday 31^rst of January 2019

Location: room G201, ENSG, Nancy

Abstract:

Le but de ce séminaire est de partager avec vous quelques aspects très intéressants des thèses auxquelles j'ai eu la chance de participer depuis Décembre: Résolution du problème inverse (Christoph Jäggli, Neuchâtel), Modélisation de surfaces complexes (Joseph Baudrillard, Grenoble), Cartes Généralisées (Valentin Gauthier, Poitiers). Je ne parlerai donc pas de l'état adjoint continu (Hamid Badri, Strasbourg), car il nous a déjà été présenté l'an dernier par Fred Delay et Philippe Ackerer.

Speaker(s): Philippe Renard

Date: Tuesday 12^th of March 2019

Location: amphitheater H, ENSG, Nancy

Abstract:

Groundwater resources are heavily used on earth for drinking water supply and agriculture. They are endangered by overexploitation and contamination. To manage and protect them, it is often important to model aquifers with an apropriate level of details, and most often the main difficulty is to represent geological heterogeneity. How to represent the geological heterogeneity in groundwater models and is it worth to do it are the main questions that will be discussed in this presentation with a pair of practical examples in fluvio-glacial systems.