Speaker(s): Guillaume Caumon

Date: Thursday 20^th of June 2019

Location: room G201, ENSG, Nancy

Abstract:

In this bibliographic seminar, I will present some recent work on structural uncertainty done in Nice (Thea Ragon's PhS) and UWA (Evren Pakyuz-Charrier's paper). Ragon proposes a way to include fault geometric uncertainty when inverting seismic rupture models from interferometry (SAR) data. Pakyuz-Charrier proposes a topological distance to cluster stochastic structural models obtained by data perturbation and implicit modeling.
In the seminar, I will summarize and discuss these two approaches.
Docs: https://www.solid-earth-discuss.net/se-2019-78/#discussion
Et https://academic-oup-com.insu.bib.cnrs.fr/gji/article/214/2/1174/4996353

Speaker(s): Paul Baville

Date: Thursday 23^rd of May 2019

Location: room G201, ENSG, Nancy

Abstract:

As a repetition of my oral presentation EAGE, I will present some results obtained during my internship graduation at OMV. These results have been summarized in an EAGE extended abstract whose authors are Paul Baville, Jörg Peisker (OMV), Guillaume Caumon.

This paper addresses stratigraphic uncertainty and its impact on subsurface forecasts. For this, we introduce a new assisted automatic method which detects possible sequence boundaries from well log data. This method uses multi-scale signal analysis (discrete wavelet transform) to compute the probability density of finding maximum flooding surfaces and maximum regressive surfaces as a function of depth. It then recursively decomposes the studied stratigraphic section into sub-intervals where the analysis is repeated. We applied this method on a shallow marine wave dominated silicoclastic reservoir located in the Vienna Basin. We observe that several reservoir models with different stratigraphic layering (keeping all other parameters constant) have a different reservoir behavior. This allowed us to locally resolve the mismatch between measured and simulated tracer tests. This illustrates the significance of stratigraphic uncertainties in reservoir modeling and the role of automatic methods to help assess and reduce these uncertainties.

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): 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): {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): {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): 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.