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1. An Example of a Regional Geologic Evaluation
of Argillite for Disposal of HLW and SNF:
Cretaceous Shale of the Northern Great Plains
Frank Perry
Rick Kelley
Los Alamos National Laboratory
SFWST Working Group Meeting
May 2017
Milestone: M4SF-17LA010504061, Regional Geologic Evaluations of
Argillite for Disposal of DOE-Managed HLW and SNF
Los Alamos Unlimited Release LA-UR-17-24057

2. 2
Distribution and Depth of Selected Shale
Formations in the US
May 2017
Pierre Shale
• Accessible depth, large extent
• High clay content
• Stable tectonic setting with minor
deformation
• Not a target for oil/gas exploration
Pierre
Some shales are more
desirable as host rocks than
others

3. 3
Shales and Oil & Gas Production
May 2017
• Much of the Pierre has few
boreholes
• Boreholes are concentrated in
basins and target deeper
formations below the Pierre

4. 4
The Pierre Shale Example in Perspective
 The Pierre Shale is likely one of many shales that have the
potential to successfully host a geologic repository and meet
requirements for long-term repository safety
 This regional evaluation is not intended to advocate or
recommend the Pierre Shale as a potential host rock
May 2017

5. 5
Regional Evaluation of the Pierre Shale
Use available data and GIS methods to evaluate the features,
events and processes that could affect long-term repository
performance in the region.
 Regional variations in depth and thickness of the formation
 Internal stratigraphy (formation members, lithologic variations, etc)
 Formations above and below the Pierre Shale, including aquifers
 Regional hydrology and hydrogeochemistry
 Potential siting issues that are part of the geologic and cultural
environment (e.g., natural hazards, oil and gas exploration,
population distribution)
 Pore fluid pressure anomalies due to formation loading or
unloading (e.g., glaciation, erosion; Neuzil 2015, GRL)
 Fractures and faults – can sealing behavior be assumed?
May 2017

6. 6
Outcrops of Pierre Shale – Badlands
National Park South Dakota
May 2017
Tertiary Sediments
Pierre
“The term "shale" often is used imprecisely
for any clayey fine-grained sedimentary
rock… The Pierre Shale… consists only
partly of fissile, fine-grained, clayey rock
that is properly called shale by almost any
definition. Much of the formation consists of
claystone having little fissility.” (Schultz et
al., 1980)

7. 7
70% clay
Pierre
Properties of the Pierre Shale
 More clay-rich (~70%) than most other shales
 High clay content equates to rock with low strength and ductile and self-sealing
behavior
 Because fractures are expected to seal, transport dominated by diffusion
 Deformation of excavations in low-strength shale would require concrete linings to
stabilize openings (Nopola 2013; Hardin 2014)
May 2017
Bourg (2015). Sealing Shales versus Brittle Shales: A Sharp
Threshold in the Material Properties and Energy Technology
Uses of Fine-Grained Sedimentary Rocks
Quartz+
Feldspar
Carbonates

8. 8
Stratigraphy of the Pierre Shale
 Characterized by thick units of marine
shale interrupted by laterally
discontinuous layers of coarser grained
siltstones and sandstones
 A “generic” stratigraphic section should
include at least one coarser grained unit
May 2017
From Schultz et al. (1980)

9. 9
Generalized Regional Stratigraphy to Support
Defense Waste Repository Modeling
May 2017
Depth (m)
90
675
Perm. K (m2)
515
930
1200
1e-19
1e-13
1e-13
1e-14
1e-20
1e-17
1e-15
repository
1e-20
siltstone
marine shale
marine shale 1e-19
Pierre
Shale
(585 m thick)
Fox Hills SS
Dakota Group
overburden
Niobrara Chalk/limestone
Carlile & Graneros Shales
Lower shales and SS

10. 10
Stratigraphy employed for
Defense Waste Simulation
May 2017
Fox Hills SS
Silty shale
Shale
Niobrara
Dakota SS
Shale
Shale
Shale
Courtesy of Emily Stein

11. 11
Depth and Thickness of the Pierre
Shale
May 2017
500
meters thickness

12. 12
Pierre Shale & Oil and Gas Exploration
May 2017
Black
Hills

13. 13
Pierre Shale & Population Distribution
May 2017

14. 14
Seismic Hazard
May 2017
Pierre
Extent

15. 15
Regional Groundwater Flow System
May 2017
• Lower Cretaceous (Below
Pierre) – Dakota
Sandstone & Equivalents
• Upper Cretaceous (above
Pierre) – Fox Hills
Sandstone
From: Downey and
Dinwiddie (1988), USGS
Professional Paper 1402-A.
Pierre Shale

16. 16
Chloride Concentration in Shales
May 2017
Pierre
Repository depth

17. 17
Summary
 The Pierre Shale is representative of a group of Cretaceous Shales
with desirable properties for repository siting (e.g., formation
thickness, depth and extent, clay content, sealing behavior,
hydrocarbon potential)
 Documenting and assessing publically available regional geologic,
hydrologic and geochemical data relevant to evaluating the long-term
performance of a repository
 Integration – collaborating and providing input for GDSA/DWR
simulations (stratigraphy, host-rock properties, features of the
geologic environment)
May 2017

18. 18
Backup
June 2016

19. 19
Potential Siting within the Pierre Shale
based on Formation Geometry
May 2017
500
meters thickness

20. 20
Pierre Shale Depth and Thickness
May 2017