Speaker: Franck Amoih

Date: Thursday 1st of December 2022, 1:15 pm.

Abstract:
La récupération assistée du méthane des gisements houillers par injection de CO2 (CO2-ECBM) est largement proposée comme moyen pour la transition énergétique et pour la réduction du CO2 atmosphérique. Dans le cadre du projet de recherche et développement REGALOR, un des axes de recherche consiste à étudier la faisabilité de l'extraction du méthane du bassin houiller lorrain par CO2-ECBM. Les résultats expérimentaux d'un échantillon de charbon bitumineux (Box 18), riche en matières volatiles provenant de Folschviller (France) sont comparés à un échantillon de charbon subbitumineux (TH01) provenant de La Houve (France), utilisé comme référence car il a été identifié comme un bon candidat pour le CO2-ECBM. Différentes techniques telles que les isothermes de sorption, les courbes de percée et les analyses thermogravimétriques ont été utilisées dans ce travail afin d'évaluer les quantités adsorbées de CO2 et de CH4 et d'étudier l'influence de l'eau et de la température respectivement. Les isothermes d'adsorption ont été obtenues par méthode volumétrique à 30°C avec des pressions allant jusqu'à 50 bars et décrites au moyen des modèles de Langmuir et de Tόth. Le Box 18 adsorbe plus de CO2 et de CH4 que le TH01. La même conclusion est obtenue avec les courbes thermogravimétriques et de percée pour le CO2. Ces résultats pourraient être expliqués par le vide (%) dans chaque échantillon. En effet, la porosité par intrusion de mercure obtenue sur un échantillon cubique de charbon d'environ 1 cm3 a montré que l'échantillon Box 18 contient plus de vides (8%) que TH01 (5,6%) et que les pores dominants dans ces échantillons sont ceux de diamètre inférieur à 0,002 microns. Le modèle de Tόth s'adapte mieux aux isothermes d'adsorption expérimentales du CH4 et du CO2 que le modèle de Langmuir, ce qui prouve que la surface du charbon est hétérogène (n 0,2). Les affinités (αL) pour le CO2 et le CH4 calculées à partir des modèles de Langmuir ont montré que le Box 18 a plus d'affinité pour le CO2 et le CH4 que l'échantillon de référence TH01. Les enthalpies d'adsorption obtenues par analyses calorimétriques ont montré une physisorption pour les interactions gaz-charbon et les valeurs pour le CO2 étaient plus élevées que celles pour le CH4. Les analyses thermogravimétriques réalisées jusqu'à 85°C ont également montré que la capacité d'adsorption du CO2 diminue avec l'augmentation de la température. Les courbes de percée réalisées à température ambiante à différents pourcentages d'humidité (0, 10 et 50%) sur 8,5 g de poudre de charbon, ont montré que l'eau a un effet néfaste sur l'adsorption du CO2. Les premiers essais d'adsorption dans une cellule oedométrique à volume constant et à température ambiante sur de la poudre de charbon pré-compactée (TH01) ont montré que la matrice de charbon adsorbe une quantité de gaz qui est fortement influence par la température. Des tests de gonflements sur le Box 18 ont montré que celui se dilate en presence de CO2 du fait de l’adsorption et se compacte en presence d’argon (gaz inerte) du fait du fait du couplage hydro-mécanique.

Speaker: Enrico Scarpa

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

Abstract:
Channelized turbidite systems are often gathered into complexes and display various stacking patterns. Their internal architectures represent one of the fundamental properties of a reservoir because they control the connectivity of high-permeability and low-permeability of sedimentary bodies. Some works have analyzed the static connectivity of various stacking patterns; however, few have quantitatively evaluated the dynamic implications of different stacking patterns on fluid flow circulation. In this work, we investigate the impact of different classes of geostatistical modeling methods on static and dynamic connectivity using several metrics. The stacking patterns are generated with an object-based method using Lindenmayer systems. 300 stochastic realizations are grouped into three categories: disorganized stacking channels, disorganized stacking conditioned to a vertical sand proportion map, and organized stacking reproducing channel vertical and lateral migration. To study the hydrodynamic responses, we set a two-phase system containing oil and water. We perform reservoir simulations in all stochastic scenarios and compute the connectivity on the simulations grid to determine the statistical relationship between metrics. This approach facilitates the comparison among flow simulations. It highlights a delay of water breakthrough time in disorganized stacking patterns and a less optimistic recovery efficiency in organized stacking patterns. Our study confirms the positive forecasting bias observed in customary geostatistical modeling that overestimates the actual reservoir connectivities.

Speaker: Omar Rodriguez Villarreal

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

Abstract:
Humanity faces great challenges from climate change and finding the right solutions will require new contributions in geotechnics and fracture mechanics. It will require the implementation of satisfactory solutions based on a better understanding of subsurface properties and behavior, monitoring of geo-material behavior, and management of geotechnical and geo-environmental processes. According to the United Nations Convention on Climate Change, one way to mitigate climate change is to reduce greenhouse gas emissions, as established in the 2015 Paris Agreement, which aims to control long-term temperature increases by regulating the production of greenhouse gases. One way to achieve such a goal is to use renewable energy resources, such as geothermal energy. In this presentation, we focus on presenting the benefits of the exploitation of Enhanced Geothermal Systems (EGS). An EGS can be considered a subway heat exchanger designed to extract geothermal energy. The performance of these systems can be improved by increasing the permeability through the judicious application of fracture mechanics. Under this approach, it is important to know the physical parameters of the rock, one of them being the so-called fracture energy. In addition, Mexico is one country with the greatest geothermal potential in the world, this clean and renewable source of energy is little exploited, an example of this is that in Mexico there are only five geothermal power plants. 

 

Speaker: Ahmad Mostafa

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

Abstract:
Coal is fractured by nature; it is a dual porosity/permeability system made up of a porous matrix surrounded by fractures known as (figure (1), scale II). The orientation of this quasi-orthogonal cleat network including tensile fractures or face cleats, and compressive and strike-slip fractures or butt cleats depends on the principal stress’s direction (Laubach et al., 2017) and provides pathways for fluid flow with apertures up to 100 microns. In contrast, methane gas is stored within the low porosity coal matrix with pore sizes generally varying from a few to several dozens of nanometers (Li et al., 2017) (Wang et al., 2018). The model implemented in the open-source software Yade DEM (Smilauer et al., 2015) is based on the hydro-mechanical model proposed by (Catalano et al., 2014). The coal matrix is treated as an assembly of bonded particles interacting one with another through elastic-brittle contact laws as initially proposed by (Scholtes and Donze, 2013). The pore space is discretized into tetrahedra, generated from a regular triangulation of the particle’s centers. Knudsen and surface diffusions as well as sorption processes are modeled considering the coal matrix as a microporous material. 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 interpore flow. 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) (Vandamme et al., 2010). The cleat system is considered as a discrete fracture network where a single-phase advection flow takes place. The ultimate goal of my PhD thesis is to combine the models describing the different transport processes at stake in both the coal matrix and the cleat network to provide a multi-scale model able to simulate the hydro-mechanical behavior of coal in the context of coal bed methane recovery.

Speaker: Mariam Joundi

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

Abstract:
Les joints rocheux sont des discontinuités dans les massifs rocheux représentant des sources d'instabilités mécaniques. La formation de ces joints varie d’un massif à un autre en fonction de l’intensité des contraintes, de la rhéologie des matériaux, de la présence ou non de fluides, de l’histoire géologique et le chemin de chargement suivi par les matériaux, etc. La morphologie des joints rocheux et le comportement mécanique de la matrice sont reconnus comme des éléments clés contrôlant le comportement mécanique du joint, notamment en cisaillement, incluant ses phases pré-pic et post-pic ainsi que sa dilatance. Ce travail étudie le comportement en cisaillement et les processus d'endommagement des joints rocheux sollicités mécaniquement à l’aide du logiciel UDEC. Des joints de morphologies différentes et de matrices intactes variées sont explicitement simulés dans des essais de cisaillement direct sous plusieurs valeurs de contrainte normale appliquée. L'effet de la magnitude de la contrainte normale appliquée, de la morphologie du joint et des propriétés mécaniques de la matrice intacte sur le comportement au cisaillement du joint sont évalué. L'analyse numérique a montré que sous faibles contraintes normales, le comportement est contrôlé par le glissement de la surface du joint. Dans ce cas, le déplacement normal reflète la géométrie de la surface du joint. Alors que sous contraintes normales plus élevées, un déplacement normal relativement limité est observé en raison du processus de dégradation des aspérités. Il a été constaté que les valeurs de la résistance au cisaillement maximale et résiduelle augmentent lorsque la contrainte normale appliquée augmente. La résistance au cisaillement augmente également pour une matrice plus rigide. En outre, il a été prouvé que la présence des aspérités augmente la résistance au cisaillement globale des joints.

Speaker: Coffi Gbewade

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

Abstract:
The Callovo-Oxfordian (COx) claystone in Meuse/Haute-Marne (France) is considered as a potential host rock in the French concept of high-level radioactive waste disposal at great depth. The excavation of galleries or micro tunnels in this host rock located at a depth of 500 meters in Bure (in the Meuse department), creates a fractured zone around them called the Excavation Damaged Zone (EDZ). The heat generated by waste could affect the favorable properties for containment of this host rock, especially its transport properties. The overpressure generated by the difference between thermal expansion coefficient of pore water and the solid rock skeleton could induce fractures opening or propagation in the near field (i.e., in the EDZ), altering the permeability. Then, laboratory experiments need to be performed to study the effects of increased temperature on the mechanical behavior of the COx claystone. These effects could be related to the evolution of the effective stress due to the temperature increase and to the modification of the physical properties of rock-forming minerals. Deviatoric (uniaxial and triaxial) compression tests are carried out in laboratory on cylindrical samples of the COx Claystone with a diameter of 20 mm and a heigh of 40 mm. Tests are performed under different temperatures from 20°C to 100°C to study the impact of temperature increase on the mechanical parameters of the host rock. The samples are cored in two directions, parallel and perpendicular to the bedding plane. The tests are carried out in a conventional triaxial cell equipped with two heating collars connected to a heat generator to apply the temperature imposed on the system. Triaxial tests are performed at low confining pressures (0 and 4 MPa) representative of the near field conditions (i.e, in the EDZ). Confining pressure is generated by a syringe pump while the axial stress is applied using a hydraulic press. Axial and lateral deformations are continuously measured during the mechanical loading using strain gauges. The deviatoric compression tests are performed under controlled displacement in order to characterize the post-peak behavior. Unloading-reloading cycles are performed at different stress levels in order to estimate the evolution of elastic properties. Uniaxial tests performed at temperatures ranging from 20 to 100°C, for both directions (parallel and perpendicular to the bedding) showed a significant decrease in the peak resistance due to the temperature increase. This decrease in the peak resistance is almost non-existent on triaxial tests (4 MPa confining pressure) in the parallel orientation, thus showing the impact of confining pressure. Nevertheless, an increase in the peak resistance is observed for a temperature of 150 °C for both cases. Further tests will be necessary by adjusting the thermal loading rate and the time between the thermal and mechanical loading, in order to see their impact on the mechanical properties of the COx claystone.

Speaker: Paul Marchal

Date: Thursday 29th of September 2022, 1:20 pm.

Abstract:
Large volume of scientific and technical data have been acquired within research & development projects carried out by Orano and the Université de Lorraine. Throughout this long-term collaboration, top-ranked articles have been published based on genuine datasets resulting from specialized analyses, in particular mineralogy, isotope geochemistry and fluid composition. Samples are stored in a well referenced lithothèque and regularly used for new batches of analysis. These results have largely contributed to the knowledge of the unconformity related deposits and are considered as key parameters for defining new projects, constraining any modelling and defining machine learning analysis strategies. In order to provide access to these numerical datasets through Otelo and to connect to the Orano standards under acQuire, a joint-project for data valorization has been set up in order to develop semi-automated methods for historical data integration and design of database templates. This project aims first to provide standards methods and templates to help new data integration into Otelo’s data repository and secondly to build tools to format and integrate historical datasets. The application of these methods and standards contribute to making datasets easier to find, accessible, interoperable and reusable (FAIR Principles). For dataset, we focused especially on drillhole data analysis, i.e. data associated with sampling on cores. Concerning new data integration, initial work was the redaction of good practice guidelines1 for data management based with focus on: Explicit & coherent data naming; access & centralization of all the necessary data; use of international standards; minimization of useless duplicates & blanks. To implement, we elaborated a standardized data template containing all required metadata data fields, in order to generalize for each new project, the realization of an integrable data file collecting all samples analysis data. Then, based on established models and templates, we designed a JavaScript web-application, on the one hand to help new file edition & also to assess historical data files quality and on the other hand extract information from sparse files. We had also implemented a geographical visualization tool based on drillholes. It allows to compare data from different projects & to extract samples lists according to available attributes, either it’s about project metadata or analysis data values.

Speaker: Nathan Amrofel

Date: Thursday 15th of September 2022, 1:15 pm.

Abstract:
A full understanding of the migration behavior of corrosion gases in clay rock is of fundamental importance for the reliability of scenarios predicting the long-term evolution of geological repositories. Due to the low permeability of host clay rock, the produced gas will accumulate as a distinct phase until the pressure becomes large enough. The high pressure generated will desaturate the surrounding clay rock by displacement of pore water far along gas paths, but also by the diffusion of water vapor through the gas. In order to better understand the impact of key transport processes occurring in gas flow in clay material, a pore-scale numerical study taking into account the capillary-dominated two-phase flow, the diffusion of water vapor in the gas phase and specific features of nanoporous materials such as kelvin effect is proposed. The work has been carried out using the Smoothed Particle Hydrodynamics (SPH) method, a Lagrangian and meshless method which has emerged as an efficient and reliable tool for simulating complex fluid flows. A drying algorithm with Kelvin effect, which drives the thermodynamic equilibrium between the fluid phase and the gas phase at nanoscale, has been implemented in a two-phase flow SPH code, initially developed at IRSN.

Speaker: Narges Dashtbesh

Date: Thursday 23rd of June 2022, 1:15 pm.

Abstract:

Understanding and modelling contaminant transport is necessary to assess the lifetime of pollution sources and their severity and optimize the remediation strategies. The transfer of contaminants from the NAPL (Non-Aqueous Phase Liquid) phase to the aquifer is a multi-scale problem driven by mass transfer between both phases and is generally described by local non-equilibrium models. While the mass exchange coefficient, an important property in such models, play a key role in the fate of the pollution source, it is usually approximated by a constant value estimated from empirical correlations. However, it generally shows a transient behaviour and can evolve with NAPL phase composition and relative solubilities, which remains poorly studied. In this work, we upscale numerically this effective property from 2D pore-scale numerical simulations. We study the impact of different factors on the form and behaviour of the mass exchange coefficient in the presence of a multi-component NAPL source depending on whether the internal mass transfer is limiting. The potential implications of replacing this time-and-space-dependent mass transfer coefficient with a constant and unique value are discussed.