The document summarizes research being conducted at Lawrence Berkeley National Laboratory (LBNL) related to deep borehole disposal of nuclear waste. It discusses 6 projects: 1) modeling the geologic framework for deep boreholes, 2) measuring permeability in fractured rock cores, 3) seismic imaging of fractures, 4) modeling thermal, hydrologic, chemical processes, 5) laboratory experiments on borehole damage zones and seals, and 6) modeling seals and the disturbed zone using thermo-hydro-mechanical coupling. The research aims to further scientific understanding of deep borehole disposal concepts through field data collection, lab experiments, and computational modeling.

1. Spent Fuel and Waste Science and Technology
LBNL Deep Borehole Research
Summary
Patrick Dobson
Lawrence Berkeley National Laboratory
SFWST Working Group Meeting
May 24, 2017

2. Spent Fuel and
Waste Science and
Technology
LBNL Deep Borehole Projects FY17
 Deep Borehole Geologic Framework Model Support
 Borehole Study: Anisotropic Permeability of Swedish COSC-1
Cores
 Laboratory Experiments for Deep Borehole Studies for Seals
and DRZ
 THM Model of Seals and Disturbed Zone
 THC Model for Evaluating Competitive Processes that Affect
the Migration of Radionuclides
 Borehole Detection & Characterization of Fractures & Faults
with Near-Field Seismic Imaging

3. Spent Fuel and Waste Science and Technology
Borehole Study:
Anisotropic Permeability of
Swedish COSC-1 Cores
Sharon Borglin, Christine Doughty, Timothy
Kneafsey
May 2017

4. Spent Fuel and
Waste Science and
Technology
The Flowing Fluid Electric Conductivity
(FFEC) Logging Method
 Peak height is
proportional to
product of inflow
rate q and formation
salinity C
 Flow up the wellbore
will cause peaks to
skew upward,
proportionally to Sq
 Model peak growth
with computer code
BORE II to fit
observed FFEC
profiles and thereby
infer parameters of
inflow zones
Parameters that can be estimated for each
hydraulically conductive inflow zone:
 Depth z
 Inflow rate q
 Formation water salinity C (~ to FEC)

5. Spent Fuel and
Waste Science and
Technology

6. Spent Fuel and
Waste Science and
Technology
Objectives
 Understand influence of
effective stress on anisotropic
fracture transmissivity on
fractured core from Swedish
borehole COSC-1
 Determine anisotropic
permeability by flowing
between pairs of points on
opposite sides of the fracture
 Repeat experiment with
multiple flow rates and at a
series of effective stresses to
examine permeability
dependence on confining
pressure, including hysteresis
 Compare laboratory-measured
results to those inferred from
Flowing Fluid Electrical
Conductivity (FFEC) Logging
conducted in the field

7. Spent Fuel and
Waste Science and
Technology
Experiments on Core 84-Z
 Selected because it was
from a shallow depth
(338.5 m) - reproducing
effective stress state with
confining pressure is
feasible
 Transmissivity variation
with confining pressure
was reasonable, but
transmissivity was orders
of magnitude higher than
obtained from FFEC
logging
 Visual examination of core
shows that fracture does
not mate tightly, possibly
different from field
conditions
X-ray CT cross-section of 84-
Z fracture – with no confining
pressure
Effective Stress

8. Spent Fuel and
Waste Science and
Technology
Experiments on Core 401-1
 Core is from a greater
depth (1244 m) requiring
higher effective stresses
 Visual inspection shows
better mating fracture
than for 84-Z
 T is comparable to values
obtained from FFEC
logging
 Effective stress was
increased from 7.5 to 20.6
MPa, showing decreasing
T. When pressure
returned to 6.8 MPa T did
not return to original
values.
 T varies by flow path
direction path with 1 to 5
> 2 to 6 > 3 to 7 > 4 to 8
(no flow through this
path)
X-ray CT cross-section of 401-1
fracture – with no confining
pressure
Effective Stress
Permeable fracture

9. Spent Fuel and
Waste Science and
Technology
Current Work – Examine Borehole
Images
 Identify core
sample location
by core section
name shown in
image and visual
appearance of a
prominent
fracture (vertical
arrows)
 Identify FFEC
peak location by
z value shown in
image
(horizontal
arrows) dashed
line is tiny peak
that was not
analyzed
 Look for
signatures
distinguishing
flowing fractures
from non-flowing
fractures
– Only 13 FFEC peaks
between 200 m and
1300 m depth
– Many non-flowing
fractures
84-Z
401-1

10. Spent Fuel and
Waste Science and
Technology
Potential Future Work
 Collaborate with Uppsala University
– Comparison of isotropic confining pressure used in the laboratory vs. the actual
effective in situ stress state
– Developing means of improving depth calibration of FFEC logs; matching the
depths of different logs conducted at different times and conditions to the
accuracy of one meter or less out of 2500 m is not easy
 Optimize laboratory procedures
– Explore different materials and fabrication methods for silicone sleeve that
surrounds core – must allow inflow and outflow from multiple ports, no leakage
around the perimeter of the core, and application of desired stress state
– Examine core-extraction and core-handling procedures to improve fraction of
cores that are analyzable in laboratory
– Create a core with an artificial fracture for controlled laboratory experiments
 Improve BORE II, code used to analyze FFEC logs
– Modernize user interface and graphical display
– Add features to enable analysis of non-ideal systems, making code more broadly
useful

11. Spent Fuel and Waste Science and Technology
Laboratory Experiments for Deep Borehole
Studies for Seals and DRZ
Seiji Nakagawa
Sharon Borglin
Tim Kneafsey
Energy Geosciences Division, Earth and Environmental Sciences Area
Lawrence Berkeley National Laboratory

12. Spent Fuel and
Waste Science and
Technology
Waste
Packages
Drilling-
Induced
Damage
Zones
Sealed
Borehole
Borehole
Breakout
Tensile
Fracture
 Reproduce and examine the geometry of damage
around a borehole within tight, crystalline rock, formed
under high stress
 Determine the hydrological properties of the damage
zone
 The hydrological-mechanical-chemical (HMC) changes
of the damage zone and the seal materials (cement,
bentonite) via diffusion and transport of fluid (water),
once the seal is placed within the borehole
Outline
Major Challenges of Lab Study→ Scaling
 The expected field borehole diameter is ~0.5 m, much
larger than typical lab experiments
 Mineral grain size is expected to play an important role
in determining the fracture size and geometry, and
permeability of the induced damage zone
 Tight crystalline rocks are very strong (uniaxial
compression strength >100‒200 MPa)
*breakout in competent
sandstone
Objectives

13. Spent Fuel and
Waste Science and
Technology
 To conduct laboratory borehole breakout experiments using ~1cm-diameter analogue
boreholes, ultra-fine-grain, Black Arkansas Novaculite was used (grain size~10μm)
 5 cm x 5 cm x 1.2 cm novaculite slabs were subjected to true-triaxial stresses to induce
borehole breakout while monitoring acoustic emissions
Approach and Results I: Scaling
by Grain Size
 In spite of repeated attempts, to this day no breakout has been produced (the rock was too
strong and tough). For this reason, we had to abandon/revise this approach
Tensile
crack
AE monitoring
Maximum borehole wall stresses up
to 839 MPa were applied
(Novaculite uniaxial compression
strength >400 MPa)
5.08 cm
Tensile
failure
Novaculite slab sample
with a center hole
No
breakout!
10 μm

14. Spent Fuel and
Waste Science and
Technology
 Typical crystalline rocks’ (such as granite’s) mineral grains are too large for lab experiment
 Considering the localized nature of borehole breakout (esp. in crystalline rock), only a part of the
borehole may need to be tested/examined
 Using a “shaped” samples, breakout experiment in granite (Stripa Granite) has been conducted
Approach and Results ll:
Modified Geometry
“Shaped”
granite core
Breakout on the
surface
Uniaxial
compression
a
b
c
d
a
b
c
d
Uniaxial
compression
X-ray CT images of
fractures in
“breakout”
• Uniaxial stress
= 184 MPa
• Max stress
concentration
=~2 x 184 MPa
Fracture

15. Spent Fuel and
Waste Science and
Technology
Approach and Results ll:
Modified Geometry
5.08 cm
10.2cm
Radius=25.4 cm
σyy stress
concentration
Shaped
Slab
Borehole
Shaped
Slab
Borehole
σθθ σrr(hoop stress) (radial stress)
 Extending the concept of shaped-core experiment, a breakout experiment can be done using a
slab sample with cuts with the same radius (~25 cm) as the field borehole (experiment in
preparation)
 The stress state near the wall closely resembles a borehole subjected to far field stresses
(horizontal principal stress ratio=2:1)
 Limitation: Near wall-surface breakout
Wall Wall
(Stresses along horizontal center line)

16. Spent Fuel and
Waste Science and
Technology
Path Forward
 Shaped core/slab method will be used to produce analogue borehole-
breakouts close to the surface of a field-scale borehole
 Although the scaling is not ideal, a sample containing a whole borehole still
needs to be used for studying the damage away from the borehole wall,
using fine-grained (but weaker) rock
 Using samples containing a damage zone (borehole breakout), hydrological
tests (permeability characterization) are planned for FY2017. Geometry of
the slab samples is well suited for this test.
 In FY2018, further hydrological tests involving cement/clay plug will be
conducted, to examine the impact of cement/fine migration and chemical
effect on the fractures in the damage zone

17. Spent Fuel and Waste Science and Technology
THM Model of Seals and Disturbed Zone
Jonny Rutqvist & Hao Xu, LBNL
Progress Update
May 2017

18. Spent Fuel and
Waste Science and
Technology
THM Model of Seals and Disturbed Zone
Objectives:
• Evaluate the evolution of disturbed
(damage) zone along the length of
the borehole during excavations,
emplacement and post-closure.
• Evaluate the function of bentonite
seals at greater depth, including
the effect of swelling and support
of the borehole walls during
thermal stress peak
Current Status:
• An anisotropic continuum damage
model have been implemented in
TOUGH-FLAC, through FLAC3D
User Defined Model
implementation
• 3D THM TOUGH-FLAC model is
being developed
3D model geometry and
2D near-field model

19. Spent Fuel and
Waste Science and
Technology
Framework of the Deviatoric Stress
Induced Damage (DSID) Model
[Xu & Arson, IJCM, 2014]
Hyper-elasticity
𝜺 = 𝜺 𝐸
+ 𝜺𝑖𝑑
4. Flow rule
1. Free energy
2. 𝑓𝑑 ( 𝛀, 𝐘)
3. 𝑔 𝑑( 𝛀, 𝐘)
𝜺 𝐸
=
𝜕𝐺𝑠( 𝝈, 𝛀)
𝜕𝝈
1. Free energy [Shao et al., 2005]
𝐺𝑠=
1
2
𝝈: 𝕊0: 𝝈 + 𝑎1Tr𝛀 Tr𝝈 2
+ 𝑎2Tr 𝝈 ∙ 𝝈 ∙ 𝛀
+ 𝑎3Tr𝝈Tr 𝛀 ⋅𝝈 + 𝑎4Tr𝛀Tr 𝝈 ⋅𝝈
2. Damage function
𝑓𝑑= 𝐽∗ − 𝛼𝐼∗ − 𝑘, 𝐼∗ = ℙ1: 𝐘 : 𝜹,
𝐽∗ =
1
2
ℙ1: 𝐘 −
1
3
𝐼∗ 𝜹 : ℙ1: 𝐘 −
1
3
𝐼∗ 𝜹 ,
ℙ1 𝝈 = 𝐻 𝜎 𝑝
− 𝐻 −𝜎 𝑝
𝐧( 𝑝)
⨂𝐧( 𝑝)
⨂𝐧( 𝑝)
⨂𝐧( 𝑝)
3
𝑝= 1
3. Damage potential
𝑔 𝑑=
1
2
ℙ2: 𝐘 : ℙ2: 𝐘 ,
ℙ2( 𝝈) = 𝐻 𝑚𝑎𝑥
𝑞= 1,2,3
( 𝜎( 𝑞)
) − 𝜎 𝑝
𝐧( 𝑝)
⨂𝐧( 𝑝)
⨂𝐧( 𝑝)
⨂𝐧( 𝑝)3
𝑝= 1
4. Flow rule
𝜺𝑖𝑑
= 𝜆 𝑑
𝜕𝑓𝑑
𝜕𝝈
= 𝜆 𝑑
𝜕𝑓𝑑
𝜕𝐘
:
𝜕𝐘
𝜕𝝈
𝛀 = 𝜆 𝑑
𝜕𝑔 𝑑
𝜕𝒀

20. Spent Fuel and
Waste Science and
Technology
THM Model of Seals and Disturbed Zone
Implemented 3D anisotropic continuum damage model based on Hao Xu’s
PhD work (Xu et al., 2015)
3D crack tensor Example of macro-cracks
around a borehole
For remaining FY17: Conduct THM simulations and analyze model
results

21. Spent Fuel and Waste Science and Technology
THC Model for Evaluating Competitive Processes
that Affect the Migration of Radionuclides
Liange Zheng, LBNL
Progress Update
May 2017

22. Spent Fuel and
Waste Science and
Technology
THC model results to date
Objectives:
• Evaluating whether denser saline water at depth inhibits upward flow induced
groundwater by thermal pressurization
• Studying how geochemically reducing conditions at depth affect the solubility of
radionuclide bearing minerals and the migration of many radionuclides
Developing the THC model
Transport processes:
diffusion and advection
Chemical processes: aqueous
complexation,
adsorption/desorption, mineral
dissolution/precipitation
Radionuclides: U
Mesh
From:
Brady et al.
(SAND2009-
4401)
k (mD) f r (kg/m
3
) Spec. Heat
(J/kg/K)
Thermal
Cond.
(W/mK)
Sedimentary
Rock
10/1.0 0.30 2750.0 1000.0 3.3
Crystalline
Bedrock
0.0001 0.01 2750.0 790.0 3.0
Damaged
Bedrock
0.2
(2.0,20.0)
0.01 2750.0 790.0 3.0
Sealed
Borehole
0.1
(1.0)
0.35 2750.0 760.0 0.8
Waste/Sealed
Well Casing
0.00001 0.0001 2750.0 760.0 46.0
Hydrological model Chemical model
Next Steps – FY17: Conduct THC simulations and
analyze model results

23. Spent Fuel and
Waste Science and
Technology
Questions from March review
Q – What processes are being evaluated that impact U behavior?
A – We consider:
Solubility of U-bearing minerals
Adsorption/desorption
Aqueous complexation, especially with carbonate
Q – Are we evaluating transport of Sr and Cs in the model, given their
importance for deep borehole disposal option?
A – These are not being considered in FY17 – we could include them for
work in FY18
Q – Have we considered the time it would take to reestablish the borehole
salinity gradient?
A – This model has been set up, but not yet run.
Q – Have we considered the impact of introducing oxic drilling fluids into
a reducing environment?
A – Not yet – this is an interesting question to explore

24. Spent Fuel and Waste Science and Technology
Borehole Detection & Characterization of Fractures &
Faults with Near-Field Seismic Imaging
Kurt Nihei, LBNL
Progress Update
May 2017

25. Spent Fuel and
Waste Science and
Technology
Objective
For effective containment of
waste in deep boreholes, it
is necessary to identify
near-borehole fractures and
faults that could potentially
compromise hydrological
and mechanical integrity.
A primary geophysical
objective is to detect and
characterize near-borehole
fractures and faults from a
single well out to distances
of ~100 m.
Freeze et al. (2015) - modified
fractures

26. Spent Fuel and
Waste Science and
Technology
Challenge
Blind Spots:
Fracture/fault imaging with the single
well acquisition geometry utilizes
reflected, converted and diffracted
waves whose path from the source to
receivers are governed by geometrical
optics.
 This restricts single well imaging to a
subclass of fractures/faults with the
required orientations for returning
seismic waves from the source to the
receivers, and to specific parts of the
fractures/faults.
Single well
seismic imaging
is possible for
dipping, well-
intersecting
fractures/faults
Single well Seismic Imaging of Well-
Intersecting Fractures & Faults
t1 t2 t3
Seismic Signatures of Fracture & Faults
Single well
seismic imaging
is not possible for
vertical, well-
intersecting
fractures/faults
• Seismic Sensitivity:
Because seismic waves are
sensitive to the presence of fractures
and faults, single well seismic
imaging is a potentially attractive
approach for detecting and
characterizing fractures and faults.

27. Spent Fuel and
Waste Science and
Technology
Approach
Removing Blind Spots:
This project is exploring a
new single well seismic
imaging approach aimed at
mitigating the blind spot
problem through the use of a
part of the seismic wavefield
that is not constrained by
geometrical optics – the
“near-field”, a zone extending
for several wavelengths from
the source where quasi-static
deformation is present, and
the sensitivity to properties is
not restricted by geometrical
optics.
frequency = 10 kHz frequency = 2 kHz
for 10 kHz wave, the
near-field extends ~2 m
from the source
Analytic Solution for a Point Pressure Source
with Displacement Receiver
for 2 kHz wave, the near-
field extends ~10 m from
the source

28. Spent Fuel and
Waste Science and
Technology
Near-Field Single Well Imaging
 Near-Field Single Well Modeling & Inversion:
To investigate the feasibility of imaging fractures
and faults from a borehole using the near-field,
we are in the process of building a near-field
inversion capability that will use multi-
component borehole sources and array of multi-
component receivers.
FY2017 Capability Development
– Activity 1 – Evolve and adapt 3D seismic code base
for borehole near-field modeling and inversion.
[current focus]
– Activity 2 - Use modeling to quantify sensitivity of
borehole seismic measurements of the near-field to
the properties of near-borehole fractures and faults.
[to be completed]
FY2018 Testing, Refinement & Validation
– Activity 1 – Test effectiveness of borehole near-field
imaging capability for fracture and fault detection and
characterization, e.g., using 50 – 2000 Hz waves to
“see” out 5 – 100 m from the borehole. Refine and
validate near-field single well fracture/fault imaging
concept.
– Activity 2 - Generate lab-scale single well fracture
data for concept validation with “real” data.
3D Code Base for Single Well Near-
Field Seismic Modeling & Imaging
f = 2 kHz simulation
(Note: This is a test model; borehole-intersecting
fractures are not a focus of this effort!)