27 kuhlman sand2016 8647 c hydrologic-modeling-v2

Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia
Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department
of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
SAND2016-8647 C
Basin-scale Density-dependent Groundwater
flow Near a Salt Repository
Kristopher L. Kuhlman
Sandia National Laboratories
Anke Schneider
Gesellschaft für Anlagen- und Reaktorsicherheit
Washington, DC
September 7-9, 2016

Outline
 Geologic/Hydrologic Background
 2016 progress
 SNL
 GRS
 Summary of issues
 Goals moving forward
2

WIPP Hydrogeology
 Repository in Salado
bedded salt formation
 >500-m thick salt unit
 Hydrogeology of
formations above salt
 Rustler Formation
 Culebra dolomite
 Magenta dolomite
 Anhydrite
 Mudstone/Halite
 Dewey Lake Red Beds
 Silt/sand stones + clay
 Dockum Group
 Silt/sand stones + clay
3

Rustler Conceptual Model
4
West
(Nash Draw)
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

Corbet (2000) WIPP Model
5
 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

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)

SNL PFLOTRAN version
8
Corbet (2000): Hydraulic conductivity [m/s]
PFLOTRAN: Permeability [m2
]

9~25x vertical exaggeration

10Original Mesh: 13-layer hexahedral (cuboid) elements (18,000 elements)
100x vertical exaggeration

SNL PFLOTRAN model
11
Without density dependence or chemistry

 SNL: data of „basin-scale“
groundwater model after
Corbet & Knupp 1996
 raster data of 10
hydrogelogic units
Basin-scale model → d³f++
d³f++
source:
SNL, SECOFL3D

d³f++ model
Dewey Lake/Triassic
Anhydrite 5
Mudstone/Halite 4
Anhydrite 4
Magenta Dolomite
Anhydrite 3
Mudstone/Halite 3
Anhydrite 2
Culebra Dolomite
Los Medanos Member
110 km
≈ 500 mN
≈ 6,000 km²

d³f++ model
Dewey Lake/Triassic
Anhydrite 5
Mudstone/Halite 4
Anhydrite 4
Magenta Dolomite
Anhydrite 3
Mudstone/Halite 3
Anhydrite 2
Culebra Dolomite
Los Medanos Member
110 km
≈ 500 mN
≈ 6,000 km²
 anisotropic grid refinement
 adapt multigrid operators

d³f++ prism grid
N source: Corbet 2000
last year: 2,614,000 tetrahedrons („coarse“ grid)
now: 54,228 prisms (coarse grid)  18,000 hexahedrons SECOFL3D
Dewey Lake/Triassic
Anhydrite 5
Mudstone/Halite 4
Anhydrite 4
Magenta Dolomite
Anhydrite 3
Mudstone/Halite 3
Anhydrite 2
Culebra Dolomite
Los Medanos Member

Free Water Table – levelset method
18
 model domain D (const.)
 phreatic surface represented by a levelset function


partially saturated zone (not solved here)
fully saturated zone (Darcy’s law)
groundwater table (moving boundary)
Ω(t)
Γ(t)DΩ(t)
D
P. Frolkovič: Application of level set method for groundwater
flow with moving boundary, Adv. Wat. Res. 2012
0),()(  txtΓx 
),( tx
Γ(t)γ,Φ(γ),Φ(x)||||  01 signed distance function

Free Water Table – levelset method
19
 model domain D (const.)
 phreatic surface represented by a levelset function


partially saturated zone (not solved here)
fully saturated zone (Darcy’s law)
groundwater table (moving boundary)
Ω(t)
Γ(t)DΩ(t)
D
P. Frolkovič: Application of level set method for groundwater
flow with moving boundary, Adv. Wat. Res. 2012
0),()(  txtΓx 
),( tx
Γ(t)γ,Φ(γ),Φ(x)||||  01 signed distance function
 ),(),(),(,),()(:)( tqtuwithtΓtuNS



Initial & Boundary Conditions
N
c=1
(saturated brine)
recharge 2.0 – 0.1 mm/year, c=0 / seepage
initial condition:
water table
14,000 years ago
source:
Corbet &Knupp 1996
closed boundaries

salt concentration
d³f++ 2016 Simulations
density-driven flow, free water table
grid level 1 (217 000 prisms) and level 2 (900 000 prisms)
velocity
water table

d³f++ 2016
 Current work:
 new BMWi-funded project GRUSS (April 2016)
 improve robustness of solvers (convergence, timesteps)
 implement volume of fluid (VOF) method to speed-up free
surface handling

Summary of Issues / Path Forward
23

Issues Encountered
24
 Old Mesh is very coarse
 PFLOTRAN and d3f have difficulty with mesh
 Mesh violates conventions regarding
 Connectivity (must build mesh “by hand”)
 Aspect ratio (2 km × 2 km × 1s-100s m)
 Anke (GRS): re-mesh using modern tools
 Kris (SNL): struggle with old mesh
 Too coarse for:
 Solute transport calculations
 Density dependent flow
 High permeability contrast (8 orders of magnitude)
 Level-Set Method for water table ≠ Richards equation
 Unsaturated flow parameters are guessed
 Recharge applied at water table vs. applied at land surface
 Water table over large area (6,000 km2)

Schedule
25
 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
 Including new features / data
 Update boundary conditions
 Update hydrological implementation and conceptual model
 Include geochemical tracers
Year1Year2Yearn

27 kuhlman sand2016 8647 c hydrologic-modeling-v2

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