Basin-Scale Density-Dependent Groundwater Flow Near a Salt Repository Anke Schneider Gesellschaft für Anlagen- und Reaktorsicherheit Kristopher L. Kuhlman Sandia National Laboratories Middelburg, The Netherlands September 5-7, 2017 Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE- NA0003525. SAND2017-9392 C.
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Basin-Scale Density-Dependent Groundwater Flow Near a Salt Repository
Anke SchneiderGesellschaft für Anlagen- und Reaktorsicherheit
Kristopher L. KuhlmanSandia National Laboratories
Middelburg, The Netherlands
September 5-7, 2017
Sandia National Laboratories is a multi-mission laboratory managed and
operated by National Technology and Engineering Solutions of Sandia LLC, a
wholly owned subsidiary of Honeywell International Inc. for the U.S. Department
of Energy’s National Nuclear Security Administration under contract DE-
NA0003525. SAND2017-9392 C.
WIPP Hydrogeology
Repository in Salado bedded salt formation >500-m thick salt unit
Hydrogeology of formations above salt Rustler Formation
East West of WIPP Shallow units High permeability Relatively fresh water
East of WIPP Deeper units Low permeability Saturated brine
Regional groundwater Flow used in WIPP PA Long-term geological
stability of salt
4
Corbet (2000) Model Domain
WIPP LWB
NM/TX Border
1996 WIPP PA Model
2004 PA Model
2014 WIPP PA Model
Scale [km]
0 10 20 4030
Corbet (2000) WIPP Model
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Most of Delaware Basin Transient Simulation
Climate variation (dry vs. wet) 14,000 y → present → 10,000 y
Model Implementation “water table” moving boundary
model ~8700 km2 region (78 km × 112 km) Coarse mesh (2 km square cells) 12 model layers (10 geo layers) 1,500 cells/layer ~18,000 elements total
Halite areas (low k)
Dissolution area
(high k)
Motivation
6
Benchmark against existing solution (Corbet, 2000) Comparison with original model
Old mesh, model parameters & boundary conditions
Include new processes, features & data Include density-driven flow (e.g., Davies, 1989) Include chemistry & mineral dissolution Investigate flow & chemistry boundary conditions Test and update hydrogeological conceptual model Incoporate current data: 81Kr GW age data, water level data
Comparison and Development of Models PFLOTRAN (SNL)
Add density dependent flow
d3f++ (GRS)
Update of Corbet model
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Corbet (2000): Hydraulic conductivity [m/s]
d3f++/PFLOTRAN: Permeability [m2]
density-driven groundwater flow
salt and heat transport
fluid density and viscosity depending on salt concentration and temperature
porous and fractured media
free groundwater surface – levelset function
sources and sinks
transport of radionuclides
decay and ingrowth
equilibrium and kinetically controlled sorption
precipitation/dissolution
diffusion into immobile pore water
colloid-borne transport
numerics based on UG, G-CSC, Frankfurt University
finite volume methods
geometric and algebraic multigrid solvers
completely parallelized (UG: scaling invest. some 100,000 proc.)
8
d³f++: distributed density-driven flow
Applications of d3f++
Applications 9
Porous media, overburden of host formations
• Gorleben Site: 2D density-driven flow and RN
transport in high saline environment
• Cape Cod: 2D contaminant transport with
pH-dependent sorption
Low permeable media
• Generic German Site in clay: 3D diffusive transport
in a low permeable anisotropic clay formation
Fractured media
• Yeniseysky site: Flow and transport in fractured rock
• Äspö (URL): Flow in the repository near field
• Grimsel (URL): Colloid-facilitated transport in clay
WIPP Site: „Basin-Scale“ model
SNL: Data of „Basin-scale“ groundwater model after Corbet & Knupp 1996
improve robustness of solvers (convergence, timesteps)
implement volume of fluid (VOF) method to speed-up free surface handling
Next steps:
increase timestep levelset method
simulation 14.000 years past
reproduction of SECOFL3D results (Corbet & Knupp, 1996)
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Reactive multiphase flow and transport code for porous media
Open source license (GNU LGPL 2.0)
Object-oriented Fortran 2003/2008 Pointers to procedures
Classes (extendable derived types with
member procedures)
Founded upon well-known (supported) open source libraries MPI, PETSc, HDF5, METIS/ParMETIS/CMAKE
Demonstrated performance Maximum # processes: 262,144 (Jaguar supercomputer)
Maximum problem size: 3.34 billion degrees of freedom
Scales well to over 10K cores18
SNL PFLOTRAN version
19~25x vertical exaggeration
SNL PFLOTRAN version
20Original Mesh: 13-layer hexahedral (cuboid) elements (18,000 elements)
100x vertical exaggeration
Issues Encountered
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Old Mesh is very coarse PFLOTRAN and d3f++ have difficulty with mesh Mesh violates conventions regarding
Regularity (Δz varies too much in space) Connectivity (must build mesh “by hand”) Aspect ratio (2 km × 2 km × 1s-100s m)
Anke (GRS): re-mesh using modern tools (LARGE) Kris (SNL): struggle with old mesh (COARSE)
Moving water table ≠ Richards equation Unsaturated flow parameters are guessed Recharge applied at water table vs. applied at land surface
CFL condition requires very small time steps Too few elements to capitalize on parallel Smaller elements → smaller time steps!
Schedule
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SECOFL3D data provided by SNL GRS begins building d3f++ model SNL begins building PFLOTRAN model SNL consults
GRS builds d3f++ model equivalent to Corbet (2000) SNL builds PFLOTRAN equivalent to Corbet (2000) GRS ‘includes’ density-driven flow SNL includes density-driven flow to PFLOTRAN
WIPP basin-scale model is: Numerically difficult Uses non-ideal mesh (pancake elements) Has complex boundary conditions
Try benchmarking simpler (2D) problems: Compare processes Use PFLOTRAN QA suite problem?