Post-doctoral position in scientific computing: high performance simulation of THM models in faulted geological systems
Orléans, Loiret
CDI
Temps-plein
Il y a 16 jours
Offer DescriptionJoining the Bureau de Recherches Géologiques et Minières (BRGM) means becoming part of the leading public establishment in the Earth sciences, bringing together 1,000 experts and enthusiastic people in 29 entities in mainland and overseas France. The aim of BRGM's work is to provide geological knowledge and an understanding of phenomena linked to the soil and subsoil, with one key aim: to meet the challenges of environmental change through innovative projects with a societal impact.Thermo-Hydro-Mechanical (THM) models in faulted porous media play an important role in many applications in geosciences. Fault networks act as corridors for fluid flows and associated mass and energy transfers and they have a preeminent role on stress (re)distribution interacting with these transfers. Anthropogenic exploitation of the subsurface (reinjection of geothermal brines, CO2 sequestration...) can lead to pressure build-ups that can potentially lead to fault reactivation with induced seismicity and/or loss of storage integrity. Reciprocally, natural stress distribution in fault networks will constrain the pathways of hot geothermal brines and the location of associated geothermal resources and ore resources that they may have deposited. Numerical modelling is a key tool to better understand, assess and control these processes. They couple the flow and energy transport along the faults and in the surrounding porous rock, the rock mechanical deformation, and the mechanical behavior of the faults related to contact-mechanics (Bonaldi et al 2022). Among available numerical tools, ComPASS ( ) is an open source parallel code initiated by LJAD-Inria and BRGM (Bureau de Recherches Géologiques et Minières - French Geological Survey) in 2015 (Xing et al 2017, Lopez et al 2018, Armandine Les Landes et al 2023, Armandine Les Landes et al 2023. It is devoted to the simulation of multicomponent multiphase non-isothermal Darcy flows on polyhedral meshes and includes complex network of faults represented as interfaces of co-dimension one coupled to the surrounding matrix. This position is part of the ANR Earth-Beat program, a joint effort between 6 partners. The main objective of the project is the understanding of the natural mineralization of uranium in faulted systems. One of the main tasks is to build up a robust and reliable tool to address THM processes in large media with explicit discontinuities.The fully detailed provisional program is as follows: the choice of the discretization for the contact-mechanics adapted to polyhedral meshes and taking fault networks into account is a key point. It will be based on a mixed formulation with face-wise constant Lagrange Multipliers accounting for the contact surface tractions at the matrix-fault interfaces. This choice allows to cope with fault networks including corners, tips and intersections and leads to local to each fault face contact conditions that can be solved with efficient semi-smooth Newton nonlinear solvers. The discretization of the displacement field will be based on a low order Virtual Element Method (VEM) with nodal unknowns taking into account the discontinuity of the displacement field at matrix-fault interfaces. VEM is a natural extension of the P1 Finite Element Method (FEM) to polyhedral meshes. Its combination with a face-wise constant approximation of the Lagrange multiplier requires a stabilisation which will be achieved by enrichment of the displacement field with an additional “virtual” bubble unknown at one side of each fault face. The solution of the sparse Jacobian system at each Newton iteration of the contact-mechanical model requires the implementation of an efficient parallel linear solver, typically using the Petsc library already available in ComPASS. We will use a parallel direct sparse linear solver but iterative algorithms could also be investigated in order to improve the efficiency of the simulations on realistic 3D geological models. The coupling of the contact-mechanical and the non-isothermal multiphase flow models will be based on iterative coupling solving iteratively both nonlinear sub-problems until convergence up to a stopping criteria. The algorithm will be typically based on a fixed-stress or undrained-split fixed point method adapted to mixed-dimensional models and designed in order to allow for the use of small time steps for the flow model time integration.Skills/Abilities :- background experience in scientific computing/applied mathematics- good skills in C++ and Python programming for HPC deployment (MPI)- familiar with collaborative tools (git)- Fluent in English (read, spoken and written), abilities in French is a plus.RequirementsResearch Field Geosciences » Geology Education Level PhD or equivalentSkills/Qualifications- background experience in scientific computing/applied mathematics- good skills in C++ and Python programming for HPC deployment (MPI)- familiar with collaborative tools (git)- Fluent in English (read, spoken and written), abilities in French is a plus.Specific RequirementsThis position will be held in BRGM, Orléans in association with the Laboratoire de Mathématiques J.A. Dieudonné (LJAD, Université Côte d'Azur, Nice). Several stays in LJAD are planned during the project.Within an environment that promotes a healthy work/life balance, particularly thanks to remote working, BRGM prides itself on providing a friendly and caring place to work.Awarded HRS4R certification in 2021, we are committed to supporting you throughout your career at BRGM. We provide you with a range of tools for developing your skills and expertise, with scope for career progression and geographic mobility.At BRGM, you will gain from such benefits as a 13th month salary, days off compensating for unpaid overtime, a company canteen, sports facilities as well as holiday and leisure options.Languages ENGLISH Level ExcellentLanguages FRENCH Level GoodResearch Field Geosciences » Geology Years of Research Experience 1 - 4Additional InformationBenefitsAt BRGM, you are guaranteed a transparent recruitment process. It is easy to apply! Please send us your application (up-to-date CV and cover letter) by 2nd april 2024.Because diversity matters to us at BRGM, all of our job vacancies are open to everyone!We will examine your application as soon as the closing date has passed. If your application is short-listed, we will contact you for recruitment interviews during which you will have the opportunity to talk with the recruitment and HR departments as well as a cross-functional department.Work Location(s)Number of offers available 1 Company/Institute BRGM Country France City orleans Postal Code 45000 Street 3, Avenue C. Guillemin BP 6009Where to apply WebsiteContact CityOrléans cedex 2 WebsiteStreet3, Avenue C. Guillemin BP 6009 Postal Code45060 E-Maila.bourguignon@brgm.frSTATUS: EXPIRED