Speaker(s): Guillaume Caumon

Date: Thursday 20th 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 23rd 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 16th 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 11th 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 11th 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 26th 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 12th 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.

Speaker(s): {mattia martinelli}

Date: Thursday 7th 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): Pierre Anquez

Date: Tuesday 21st 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.