Speaker: Capucine Legentil, Paul Baville & Zoé Renat

Date: Thursday 14th of January 2021, 1:20 pm.

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 et 3ème année (Capucine Legentil, Zoé Renat et Paul Baville).

Speaker: Xiaodong Zhang

Date: Thursday 7th of January 2021, 1:20 pm.

Abstract:

It is about a diffusive crack modeling based on the introduction of a phase field. A thermodynamically consistent framework has been primarily studied aiming at developing phase field models for elastics solids by considering the hydromechanical coupling.

Speaker: Fabrice Taty

Date: Thursday 17th of December 2020, 1:20 pm.

Abstract:

Le but de cet article était donc d’utiliser la théorie des graphes pour mieux comprendre les incertitudes liées à l’interprétation structurale. En effet, compte tenu des observations limitées et de la qualité médiocre des images sismiques, définir une architecture structurale est cependant fastidieux et est sujet à des incertitudes. Le formalisme de graphe nous permettra de trouver les associations possibles entre les différentes preuves de failles spatialement tout en utilisant des règles géologiques numériques dans le but de contraindre ces associations.

Speaker: Francois Bonneau

Date: Thursday 3rd of December, 1:20 pm and Thursday 10th of December, 1:20 pm.

Abstract:

Fracture networks (FN) are systems of complex mechanical discontinuities that dramatically impact the physical behavior of rocks. Their statistical characterization is an important first step of stochastic modeling. It is, however, a big challenge because field data are sparse and incomplete. Field observations present several biases due to sampling (censoring, truncation, orientation). The present paper concentrates on the statistical analysis of outcrops, which often may be considered as planar sections through three-dimensional FN. For the corresponding planar FN there exist well-elaborated statistical methods that yield first-order characteristics such as fracture density or fracture length distributions. Using ideas from stochastic geometry, in particular the theory of fiber processes and marked point processes, we develop second-order characteristics called pair correlation function and mark correlation function, which describe the variability of planar FN and their inner spatial correlations. Surprisingly, one of these characteristics is closely related to characteristics used in statistics of fractals applied to FN. We demonstrate the application of our ideas by field outcrops already published in the literature.

Speaker(s): Capucine Legentil

Date: Thursday 26th of November, 1:20 pm.

Abstract:

As the first step of a project to locally update three-dimensional geological models, we propose a method to robustly introduce boundaries in a triangulated geomodel. this allows the integration of new data, simulation results, or geometry perturbation to reflect subsurface uncertainties. The2D 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. We focus on the insertion of a boundary implicitly defined by an iso-value of a scalar field. The output is an updated mesh, which contains the new boundary. Distinctly from current model modification, we operate on the mesh and aim at keeping this mesh valid throughout the modifications. The cost of recomputing physical properties over the updated mesh, which depends on the model size and grid resolution, is minimal since mesh modifications are local.

To assess the impact of the model updates, we consider elastic wave propagation simulated with a Discontinuous Galerkin method. Results on a fluid contact in a reservoir show a consistent behavior and clear the path for more complex model updates and for considering these updates in solving subsurface inverse problems.

Speaker(s): Christophe Antoine

Date: Thursday 19th of November 2020, 1:00 pm

Speaker(s): Guillaume Caumon

Date: Thursday 12th of November 2020, 1:20 pm

 

Speaker(s): Lionel Bertrand & Martin Stanek

Date: Thursday 22nd of October 2020, 1:00 pm.

Abstract:

La caractérisation du réseaux de failles et des fractures associées est un élément clé pour la compréhension des circulations de fluides dans de nombreux objets géologiques. C’est particulièrement le cas pour les réservoirs fracturés où les failles sont une des cible des prospections pétrolières ou géothermiques. Pour une analyse optimale des circulations de fluides associées aux failles, il est nécessaire d’étudier les objets à toutes les échelles : à l’échelle régionale (bassin, orogène,…) pour comprendre le batî structural et l’organisation du réseaux de failles pouvant servir de drains, à l’échelle du réservoir pour caractériser et modéliser les circulations de fluides dans les coeurs de failles et les zones endommagées, à l’échelle microscopique où la microfissuration a une influence sur les interactions fluides-roches qui modifient les propriétés matricielles du réservoir. Dans ce séminaire, il s’agit de présenter les data utilisées et disponibles dans l’équipe RC de GeoRessources pour la réalisation de ces études, les résultats qui sont espérés et problématiques associées à chaque type de data.

Speaker(s): Paul Baville

Date: Thursday 15th of October 2020, 1:00 pm.

Abstract:

Assisted well correlation aims at complementing sedimentological expertise with computational rigor to increase automation, improve reproducibility and assess uncertainties during stratigraphic correlation. We propose a computer-assisted method which automatically generates possible well correlations based on facies interpretation, dipmeter data and knowledge about depositional environments.

This method uses facies interpretations and progading or backstepping trends deduced from the vertical stacking of depositional environments. These data are translated into a paleo-geographic variable inferred from depositional environments, e.g. the position along a proximal-to-distal transect. Assuming that wells have a global distality due to their position with respect to the overall basin geometry within the considered stratigraphic interval, we can interpolate a three-dimensional surface constrained by well-markers and dipmeter data acquired along wells. These surfaces represent chronostratigraphic surfaces. In a first approximation, the depositional dip direction is assumed to parallel sediment transport direction and the depositional strike direction being at a right angle to the former.

Well correlations are computed using correlation costs between all possible marker combinations aggregated by the Dynamic Time Warping algorithm. These correlation costs are based on the shape of the relative paleo-topography. Additionally, proximal facies interpreted in a distal well cannot be associated with distal facies interpreted in a proximal well, and conversely distal facies interpreted in a distal well may be likely associated with a proximal facies interpreted in a proximal well. Along the depositional strike, the method tries to associate identical or close facies with respect to distality.