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A Coupled Geomechanical, Acoustic, Transport and Sorption Study of Caprock Integrity in
Carbon Dioxide (CO2) SequestrationProject Number: DE-FE-0023223
Manika Prasad, Colorado School of MinesCo-I: Bill Carey (LANL), Ronny Pini (Imperial College)
Post-Docs & Students: Nerine Joewondo,Kurt Livo, Manju Murugesu, Mathias Pohl
U.S. Department of EnergyNational Energy Technology Laboratory
Mastering the Subsurface Through Technology Innovation, Partnerships and Collaboration:Carbon Storage and Oil and Natural Gas Technologies Review Meeting
August 13-16, 2018
2
Presentation Outline• Objectives and motivation• Experimental Updates
1. Mineralogy Control on CO2 Accessibility on Micropores of Shales for CCUS Application
2. Acoustic Measurements with CO2 saturation3. NMR studies of CO2-saturated brine4. Direct-shear experiments on shale permeability
• Accomplishments to date• (Near-) Future work
Center for Rock Abuse
Objectives
• Determine the behavior of intact and fractured caprocks when exposed to supercritical CO2 at elevated pressures
• Quantify adsorption and acoustic properties of shales with sorbed CO2
• Provide framework for monitoring, verification and accounting (MVA) efforts of CO2sequestration and its effect on caprock
Center for Rock Abuse 3
(1) CO2 Accessibility in Shale Micropores
• Gas adsorption to characterize nanopores• Samples Used• Analysis methods and Results• Application to CO2 storage
4Center for Rock Abuse
Storage capacity estimates:– Economically feasible CO2 capacity of Utica +
Marcellus + Antrim + Devonian Ohio ≈ 50 Gt(Godec et al, 2014)
– Theoretical CO2 capacity of Utica = 10 Gt (Godec et al, 2014)
– 80% storage capacity by sorption (Ambrose et al, 2012)
Motivation
Center for Rock Abuse 5Joewondo and Prasad, 2018
P. Klobes and K. Meyer (BAM, Germany)nanopores
Typically, N2gas is used
Kinetic diameters: CO2 (0.33 nm) < N2 (0.36 nm). We use CO2 to access smaller micropores than those accessible to N2
Pore characterization methods
Center for Rock Abuse 6Joewondo and Prasad, 2018
• Recommended practice (IUPAC 1985 & IUPAC 2015)• Adapted N2 adsorption to characterize shales, also compared
to WIP (Kuila, 2013)• Limited accessibility for N2 in immature oil window samples
due to blockage by bitumen (Saidian, 2015)• Limited pore accessibility dependent on mineralogy and gas
type; preferential CO2 uptake in OM (Kumar, 2016)• In presence of water, preferential uptake of CO2 only in OM
not in clay minerals (Kumar, 2016)• N2 - and CO2- derived PSD on shales with 2-21% TOC
Previous studies
Center for Rock Abuse 7Joewondo and Prasad, 2018
• Standard clay samples – benchmarking – Illite, Illite-smectite, Na-rich montmorillonite
• Producing shales in North America– Bakken (7-21% TOC), Utica (2% TOC) and Niobrara (3-5% TOC)
• Analog to caprock of CO2 storage site in the Norwegian North Sea – Agardhfjellet (12% TOC), Rurikfjellet (2% TOC)– CCS candidates
Samples Used
Center for Rock Abuse 8Joewondo and Prasad, 2018
• Require high pressure setup to measure full isotherm
• P0 > 1 atm
N2 at 77K CO2 at 273 K
• Diffusional limitations of N2molecules in narrow pores
• Underestimate micropores
Measured adsorption isotherm
Center for Rock Abuse 9Joewondo and Prasad, 2018
Bakken
Niobrara
Utica
Agardhfjellet
Rurikfjellet
Note: Opposite trend of N2- and CO2- derived pore structures;Mudrocks with high TOC have higher CO2 storage potential
N2 CO2
TOC controls on micropore volume
Center for Rock Abuse 10Joewondo and Prasad, 2018
Micropore volume measured in this workUtica = 2E-3 cc/g Agardhfjellet = 11E-3 cc/g
Assume micropores are filled with CO2CO2 density 0.6 g/cc (30 C, 8 Mpa) (van der Meer 2005)Shale density 2.4 g/cc
Calculated CO2 storage capacity in 1 m3 of shales from this workUtica (2% TOC): 2.8 kgCO2 Agardhfjellet (12 % TOC): 15.8 kgCO2
Compare with Godec et al. (2014) for the same area:Average thickness of 150 ft or 45.7 m (Refayee et al. 2016) Theoretical CO2 capacity of Utica formation
19.7 GtCO2 (this work) and 10 GtCO2 (Godec et al. 2014)
Implications for Storage Capacity
Center for Rock Abuse 11Joewondo and Prasad, 2018
Comparing CO2 and N2- accessible volumes
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0
0.002
0.004
0.006
0.008
0.01
0.012
0 5 10 15 20 25Diff
eren
ce in
mic
ropo
revo
l. (C
O2
-N2)
[cc/
g]
TOC from RockEval [wt. %]
Bakken
Utica
Niobrara
Svalbard
Excess CO2 storage depends on TOC
Joewondo and Prasad, 2018
Surface Area and Clay Content
13
• OM pores are hydrophobic• OM pore development starts at the onset of oil window• Presence of bitumen free OM pores• Cryogenic N2 blocked by nano-sized pores in organic matter
0 0.1 0.2 0.3 0.4 0.5Clay fractional weight
0
4
8
12
16
20
N2 B
ET S
SA (m
2/g)
114
11005
2
5 16
7219
3
13LG
1
44
TOC weight %0 (Siltstone)6 to 1313 to
Preferential sorption of fluids
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Quantification of hydrophilic and hydrophobic pores of shales
Preferential sorption of fluids depends on polarity of surfaces
Kumar, 2016
Sorption in shales with water
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‘dry’ Bakken
‘dry’ Illite
Illite + water
CO2 sorption at 50 °C
0 500 1000 1500 2000Pressure [psi]
0
1
2
3
4So
rptio
n E
xces
s [m
mol
/g]
Bakken + water
Kumar, 2016
Sorption in shales with water
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Illite: Water Imbibed Bakken: Water Imbibed
CO2 sorption CO2 sorption
OM
In presence of water: Illite pores take up water; CO2 fills OM pores
Kumar, 2016
Environmental Scanning Electron Spectroscopy (ESEM)
Spot Analysis
12
3
4
5
6 Darker areas: clay- and OM-
richLighter areas:
silt- rich
Center for Rock Abuse 17Murugesu, 2018
Agardhfjellet from Svalbard
Sorption in Zeolite
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Without vacuum, N2-uptake is 25% less than degassed sample
Joewondo and Pohl, 2018
Waveforms and Velocities with CO2
Center for Rock Abuse 19
-600
-500
-400
-300
-200
-100
0
100
200
300
400
15 17 19 21 23 25 27 29
Am
plitu
de [m
V]
Time [µs]
Vacuum; Vp=823.5 m/s244 psi; Vp=852.0 m/s401 psi; Vp=859.3 m/s531psi; Vp=861.8 m/s
Sample was not oven dried/degassed
Pohl and Joewondo, 2018
Frequency and Velocities with CO2
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0
10
20
30
40
50
60
0 200 400 600 800 1000
Am
plitu
de
Frequency [kHz]
Vacuum; Vp=823.5 m/s244 psi; Vp=852.0 m/s401 psi; Vp=859.3 m/s531psi; Vp=861.8 m/s
Sample was not oven dried/degassed
Pohl and Joewondo, 2018
Ultrasonic Velocities
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3
4
5
6
0 1000 2000 3000 4000 5000
Vp
[km
/s]
Pressure [psi]
Dry Butane CO2
2
2.5
3
3.5
0 1000 2000 3000 4000 5000V
s [km
/s]
Pressure [psi]
Dry Butane CO2
Sharma, 2016
Carbonate core
Seismic Velocities
Center for Rock Abuse 22
2.00
2.25
2.50
2.75
3.00
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50
Vs [
km/s
]
Log frequency [Hz]
DRY BUTANE CO2
Sharma, 2016
Carbonate core
• CO2-accessible micropore volume depends on TOC• Need to complement N2 measurements with CO2 for CO2 storage
capacity• CO2 storage capacity increases with TOC• CO2 storage capacity decreases in presence of water (clay
effect)
• Frequency content (seismic attenuation) is sensitive to gas content
• Fluid in micropores depends on mineralogy – should be accounted for in seismic inversion
Conclusions
Center for Rock Abuse 23
Synergy Opportunities– Calibrate rock physics models with partial saturation due
to mineralogy – dependent pore volumes and preferential fluid sorptions. Relevance: 4D seismic operations
– Investigate well log NMR signals for changes in fluid signatures versus changes in the rock due to rock –fluid interactions. Relevance: CCUS and Oil & Gas operations
– Joint acoustic –permeability changes with CO2 before and after shearing. Relevance: caprock changes with stress changes
– Imaging CO2 migration – student intern with SINTEF24Center for Rock Abuse
A Coupled Geomechanical, Acoustic, Transport and Sorption Study of Caprock Integrity in Carbon Dioxide (CO2) Sequestration��Project Number: DE-FE-0023223Presentation OutlineObjectives(1) CO2 Accessibility in Shale MicroporesMotivationPore characterization methods Previous studiesSamples UsedMeasured adsorption isothermTOC controls on micropore volumeImplications for Storage CapacityComparing CO2 and N2- accessible volumesSurface Area and Clay ContentPreferential sorption of fluidsSorption in shales with waterSorption in shales with waterEnvironmental Scanning Electron Spectroscopy (ESEM)Sorption in Zeolite Waveforms and Velocities with CO2Frequency and Velocities with CO2Ultrasonic VelocitiesSeismic VelocitiesConclusionsSynergy Opportunities
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