Speaker(s): Nicolas Mastio

Date: Thursday 29th of November 2018

Location: room G201, ENSG, Nancy

Abstract:

Time-lapse seismic has become a useful tool for reservoir monitoring and well stability assessment. Geophysicists have developed numerous methods to retrieve time-lapse attributes for the reservoir and for the overburden. However, these methods do not consider the physical differences between these two area during the inversion process. From a theoretical perspective, the elastic properties depend on the stress state. Consequently, this induces an anisotropy in the time-lapse velocity change which can have various origins: reservoir compaction, rocks damaging, etc.

Edgar and Mastio (2017) expose a reflection travel time tomography adapted to retrieve the time-lapse velocity change. An extension of this method which considers velocity change general anisotropy is presented and applied to a real case.

Speaker(s): Pauline Collon

Date: Friday 23rd of November 2018

Location: room G201, ENSG, Nancy

Abstract:

During this seminary, I present an overview of all the works related to the karstic systems thematic that have been carried out over the last ten years at RING. I emphasize especially two complementary aspects I worked on: the stochastic simulation of karstic systems and the statistical analysis of existing karstic networks.

Speaker(s): Modeste Irakarama

Date: Thursday 15th of November 2018

Location: room G201, ENSG, Nancy

Abstract:

I introduce a new method for implicit structural modeling. The method is based on a finite element discretization of recently proposed regularization operators for implicit modeling. A finite element implicit modeling scheme offers some geometrical flexibility as it is readily implemented on structured, unstructured, and mixed-element grids. While implicit modeling on unstructured grids is not new, the method proposed here is, to my very limited knowledge, the first implementation based on finite elements. The finite element method is routinely used to solve boundary value problems. However, because boundary conditions are usually unknown in implicit structural modeling, the traditional finite element method requires minor adjustments in order to be suitable for implicit modeling.

Speaker(s): Corentin Gouache

Date: Friday 12th of October 2018

Location: room G201, ENSG, Nancy

Abstract:

Ce séminaire sera l'occasion de faire découvrir aux 3A 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.

 

Speaker(s): Guillaume Caumon

Date: Friday 5th of October 2018

Location: room G201, ENSG, Nancy

Abstract:

Geologists and geophysicists often approach the study of the Earth using different and complementary perspectives. To simplify, geologists like to define and study objects and make hypotheses about their origin, whereas geophysicists often see the earth as a large, mostly unknown multivariate parameter field controlling complex physical processes. This chapter discusses some strategies to combine both approaches. In particular, I review some practical and theoretical frameworks associating petrophysical heterogeneities to the geometry and the history of geological objects. These frameworks open interesting perspectives to define prior parameter space in geophysical inverse problems, which can be consequential in under-constrained cases.

This seminar is associated with the eponymous book chapter published in the 2018 IAMG Handbook of Mathematical Geosciences (available for download here).

Speaker(s): Paul Cupillard

Date: Friday 14th of September 2018

Location: room G201, ENSG, Nancy

Abstract:

We present a general concept for evolutionary, collaborative, multiscale inversion of geophysical data, specifically applied to the construction of a first-generation Collaborative Seismic Earth Model. This is intended to address the limited resources of individual researchers and the often limited use of previously accumulated knowledge. Model evolution rests on a Bayesian updating scheme, simplified into a deterministic method that honors today’s computational restrictions. The scheme is able to harness distributed human and computing power. It furthermore handles conflicting updates, as well as variable parameterizations of different model refinements or different inversion techniques. The first-generation Collaborative Seismic Earth Model comprises 12 refinements from full seismic waveform inversion, ranging from regional crustal- to continental-scale models. A global full-waveform inversion ensures that regional refinements translate into whole-Earth structure.

Speaker(s): Margaux Raguenel

Date: Thursday 30th of August 2018

Location: room G201, ENSG, Nancy

Abstract:

Ce séminaire sera l'occasion de parler non pas de recherche, mais d'enseignement. Je vais ainsi revenir sur mon parcours de Doctorante Contractuelle Chargée d'Enseignement (aka DCCE), en présentant les éléments et outils pédagogiques que j'ai pu découvrir au cours de mes formations, discussions et enseignements. Je présenterai également les différentes formations proposées par l'UL en pédagogie et accompagnement de l'enseignement et sur le Label Enseignement supérieur, proposé pour les doctorants se destinant à une carrière d'enseignant(-chercheur).

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.