Speaker: Ahmad Mostafa

Date: Thursday 10th of March 2022, 1:15 pm.

Abstract:

In the last decades, pore network models (PNMs) have been widely used to study multiphase flow (e.g., (Blunt et al, 2001)) and reactive transport processes (Raoof et Hassanizadeh, 2010) in porous media, Several PNMs have been applied for modelling coalbed methane recovery but most of them do not describe the full coupling of multiple physical mechanisms involved. For instance, Jing et al. (2020) neglect the hydromechanical couplings, while Sampath et al. (2020) do not take into account all modes of diffusion as well as multiphase flow occurring in the cleat network. The objective of the PhD work is to develop a 3D discrete element method (DEM) coupled to a pore scale finite volume method (PFVM) to better understand the different mechanisms at stake during coalbed methane recovery. The method is hydro-mechanically coupled in the sense that changes in pore pressure produce hydrostatic forces that deform the solid skeleton, while deformation of the pore space induces pore pressure changes that promote interporal flow. The model describes adsorption and diffusion of gas within the coal matrix as a result of both Knudsen diffusion (pore pore) and surface diffusion (solid-solid). In addition, sorption induced deformations are taken into account by considering an additional pressure term related to the concentration of gas within the medium (the so-called solvation pressure)

Speaker: Franck Amoih

Date: Thursday 24th of February 2022, 1:15 pm.

Abstract:

Dans le cadre du projet REGALOR, deux charbons de Folschviller bitumineux (box 18 et box 109), riches en matières volatiles (classification de Copard, 2002) ont été étudiés pour leurs aptitudes dans le contexte d’une exploitation du CH4 par injection de CO2. Les résultats sont comparés à un charbon de référence, sub-bitumineux provenant de la Houve (TH01) et identifié comme étant un bon candidat pour l’ECBM (Enhanced Coal Bed Methan) dans le cadre du programme ANR-CHARCO (Defossez, 2011). Au niveau des caractéristiques étudiées de ces échantillons, la principale différence est l’indice de vide et le pourcentage de carbone organique. L’analyse des isothermes de sorption et des courbes de percées montre que nos deux charbons adsorbent jusqu’à 3 fois plus de CO2 que le charbon de référence à pression atmosphérique et température ambiante. Ces résultats sont confirmés à 10bars. En ce qui concerne le CH4, nos échantillons sont susceptibles de contenir environ 30 fois plus de méthane que le charbon de référence. L’étude de l’effet de la température sur la capacité d’adsorption du CO2 par des analyses thermogravimétriques montre une diminution de celle-ci en augmentant la température. Les courbes de percée montrent que l’eau a un effet néfaste sur l’adsorption du CO2 sauf pour l’échantillon box 109. Des isothermes de sorption du CO2 sur des charbons humides sont en cours de réalisation pour nous donner plus d’informations La description des isothermes d'adsorption par les modèles de Langmuir, Tόth et Temkin indique que celui de Tόth s'adapte mieux aux isothermes expérimentales d'adsorption du CH4 et du CO2 montrant que la surface du charbon est hétérogène (n » 0,1). Les affinités (αL et K0) pour le CO2 et le CH4 calculées à partir des modèles de modèles de Langmuir et Temkin ont montré que les échantillons de Folschviller ont plus d'affinité pour le CO2 que la référence qui présente beaucoup plus d'affinité pour le CH4.


Speaker: Jeremie Giraud

Date: Thursday 17th of February 2022, 1:15 pm.

Abstract:

In this seminar, I will present recent development from the GeoMos project. The current objective is to develop and test methodologies using automated geological modelling to ensure the geological consistency of geophysical inversion results using implicit approaches. I will present recent developments comprising the investigation of two strategies reconciling geological and geophysical modelling through: (i) the use of stratigraphic rules in geophysical inversion to stir inversion towards models honoring geological information such as stratigraphic thickness and contacts; (ii) the use of age relationships to recover measurements characterizing an unconformity. In the first case, a geological correction term is used in the inversion’s model update at each iteration, thereby adjusting the geophysical model accordingly with geological rules and data. In the second case, geological realism in inversion is encouraged by embedding automatic geological modelling in the geophysical inversion’s objective function. Preliminary results on synthetic data indicate that the approaches investigated here offer a certain degree of flexibility and can effectively leverage geological data and knowledge to derive geologically consistent geophysical inverse models.

Speaker: Audrey Bonnelye

Date: Thursday 10th of February 2022, 1:15 pm.

Abstract:

In the Earth's crust, a large part of the deformation is located at the level of fault zones. The study of faults represents a major societal challenge, both from the point of view of understanding the seismic risk, and for the mitigation of industrial risk in geoengineering (storage in geological environment or for energy production via geothermal energy). The mechanical behavior of fault gouge and adjacent wall rock is a key in understanding faulting. It is still unclear how and where does localization occur, and what are the respective roles of the damaged and intact rocks. The effect of the stress state on the rheology and on the seismic behavior, both in the damaged zone and in the fault core, is still unknown. One way to address these questions is to perform laboratory experiments in order to understand the relevant physical mechanisms. In my presentation I will show results from different types of experiment, from uniaxial tests with deformation measurements via digital image correlation (DIC) to triaxial tests with acoustic emission monitoring and aiming at unraveling field scale phenomenon.

Speaker: Julien Herrero

Date: Thursday 03rd of February 2022, 1:15 pm.

Abstract:

To assess the CO2 storage capacities of an underground reservoir, it is possible to build a three-dimensional model, and then generate a mesh before being able to run the numerical simulations that will allow to quantify the CO2 quantity that can be injected. The mesh is a discretization of the geological model in a numerical grid and represents the reservoir geometry in three dimensions, ideally built only with hexahedral cells. The generation of hexahedral meshes that are aligned at the same time on the stratigraphy, the faults, and nonconformities is generally impossible. An alternative is to generate grids composed of a majority of hexahedra. The other elements can be tetrahedra, prisms, pyramids or any polyhedra. Geological modeling software and/or mesh generation software make it possible to generate these hybrid meshes. Their use in flow simulators requires adaptations of the standard industrial workflow, and especially to describe the transmissibility factors between cells. A prototyping workflow is being developed at TotalEnergies company to perform these adaptations. Before applying the workflow on the hybrid case, it is necessary to make it work on unstructured grids, i.e., meshes composed of non-hexahedral cells, because the unstructured case need fewer technical adaptations. The objective of this work is to test and adapt this workflow to allow the use of different types of meshes in different simulators. Through the workflow application on a case study, and the generation of a tetrahedral mesh, technical improvements and process validation are performed.

 

Speaker: Francois Bonneau

Date: Thursday 27th of January 2022, 1:15 pm.

Abstract:

Fractures are very common 3D mechanical discontinuities which need to be considered to build predictive models regarding rock physical behavior.In hydrocarbon reservoirs, fracturesoften lead to lower observed recovery rates than model-based forecasts. One of the reasons for this lack of model predictivity lies in the simplifying geometric assumptions of equivalent permeability models.Nowadays, considering actual energy transition challenges such as CO2 storage or geothermal heat recovery, it is still crucial to enhance the characterization and the modeling of fractures. The RING-Team has a strong expertise in fracture characterization and Discrete Fracture Network Simulation. This knowledge is supported by software developed to be combined with appropriate meshing and physical simulator tools (partly designed by the RING-Team) to take another step toward a stochastic based workflow and better structural uncertainties assessment.

In the current seminar, you will learn about:

  1. Software: overview of applications and trainings you can use as a RING Sponsor.
  2. Fracture Characterization: focus on spatial organization of Fracture Network.  
  3. Next steps: ongoing developments and workflow integration.

Speaker:  Laura Gaillard

Date: Thursday 20th of January 2022, 1:15 pm.

Abstract:

Le DIspositif de Modélisaton analogIque TRIaxial (DIMITRI) est une presse triaxiale d’un volume utile comprimé de 2 m3 au sein duquel des galeries peuvent être excavées. Il permet donc d’étudier le comportement mécanique de modèles réduits d’ouvrages souterrains. Dans le cadre de l’étude d’un modèle réduit d’une mine souterraine dans un massif rocheux fracturé, un système d’instrumentation du dispositif doit être développé. Le massif rocheux discontinu est représenté par un matériau analogue réalisé par impression 3D combinant sable et liant phénolique. L’objectif est de proposer des solutions techniques d’acquisition des déformations et des contraintes dans des zones localisées du modèle réduit. Ainsi, seront présentés les premiers procédés à l’étude pour cette instrumentation au cœur du massif.

Speaker: Abdessamad Nait Ouhra

Date: Thursday 13th of January 2022, 1:15 pm.

Abstract: 

The rheology and dynamics of red blood cells (RBCs) under confined flows, are studied in the Stokes limit. We numerically investigated the lateral migration of a suspended vesicle (a model of (RBCs)) in a bounded shear flow. We explore the relevant dimensionless parameters to study the dynamics and rheology of a vesicle as a function of the viscosity contrast λ = ηin/ηout, where ηin, ηout denote the inner and the outer viscosities. We found that the equilibrium lateral position of the vesicle exhibits a saddle-node bifurcation as a function of the bifurcation parameter λ, which leads to a surprising acute decrease of the effective viscosity of the suspension at a critical value of viscosity contrast (λc). We found that below a critical viscosity contrast λc, the vesicle is centered, and above λc, the vesicle can be either centered or off-center depending on initial condition. This study can be exploited in the problem of cell sorting out and can help understanding the rheology of confined suspensions.

Speaker: Fabrice Taty-Moukati

Date: Thursday 6th of January 2022, 1:15 pm.

Abstract:

Building the data energy term of marked point processes is of an utmost importance. The main reason is that characterizing objects on images, in the framework of marked point processes, requires building a probability density, which is often composed of two terms. The first one is the interaction energy characterizing interactions between objects and the second one is the data energy which contains the locations as well as sufficient information of objects. The goal of our work is to detect and characterize seismic faults in the context of image analysis to deals with fault uncertainty problems. Seismic images themselves are subject to uncertainties, mainly due to processing steps as well as the limited seismic bandwidth. For these reasons, we cannot rely on a single interpretation to perform analyses of any field or reservoir, even if obtained with neural networks, since we know that this interpretation can comprise ambiguities. We also know that geological faults, as one may take a closer look at them, are not linear but damage areas composed of several small cracks. Based on the facts set out above, we adopt the foregoing approach based of segment processes to characterize and detect seismic faults. We do that since a seismic fault network can be seen as a realization of a marked point process. One of our goals is to increase the resolution of seismic faults that we seen in seismic images. For doing so, we start with fault probabilities provided by FaultNet3D [Wu et al.,2019] to better constrain the data energy term in accepting or rejecting segments.