SALT Workshop

1. 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

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

3. 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

4. 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

5. 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

6. 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)

7. SNL Progress in 2016
7

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

9. SNL PFLOTRAN version
9~25x vertical exaggeration

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

11. SNL PFLOTRAN model
11
Without density dependence or chemistry

12. SNL PFLOTRAN model
12

13. GRS Progress in 2016
13

14.  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

15. 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

16. 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

17. 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

18. 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

19. 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



20. 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

21. 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

22. 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

23. Summary of Issues / Path Forward
23

24. 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)

25. 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