This document summarizes the use of low field NMR to characterize shales. It discusses issues with characterizing nanoporous media using NMR and other methods. It shows that water in nanopores has a relaxation time (T2) between 0.1-1 ms. Diffusion NMR can be used to measure cementation exponents and tortuosity in shales. Methane adsorbed on surfaces has a large T1/T2 ratio. Organic matter, hydroxyl groups, and solids also have distinct T1-T2 signatures. The document concludes that fluid typing in shales can be achieved using T1-T2 mapping due to the weak overlap of different proton populations' signatures on such a map.
1. Renewable energies | Eco-friendly production | Innovative transport | Eco-efficient processes | Sustainable resources
Characterization of shales
with low field NMR.
M. Fleury
Energies nouvelles, Rueil-Malmaison, France SCA symposium, 8-11 September 2014, Avignon, France
2. Energies nouvelles, Rueil-Malmaison, France
Low permeability media and nanoporous
materials
From characterisation to modelling:
can we do it better?
Rueil-Malmaison, France, 9-11 June 2015
2
http://www.rs-lowperm2015.com/
End of Call For Papers: 28 Nov. 2014
LowPerm2015: platform for exchange and interaction between research and
industry players from a variety of different disciplines such as geological
formations (shale, tight sandstone or carbonates, etc.), concrete engineering,
polymer sheaths for pipelines, nanofiltration for produced water treatment,
heterogeneous catalysis, etc.
These very different applications all face the same challenges: the
characterisation and modelling of these media and materials and the
associated transport mechanisms at different scales and potentially enhanced
by the confinement.
3. Energies nouvelles, Rueil-Malmaison, France
Characterization issues
Pore sizes down to 1 nanometer
Medium to low porosity (5-15%)
Presence of organic matter and associated
porosity
Liquid permeability down to 1nD, gas flow
dominated by Klinkenberg effect
Simple measurements such as porosity or
cementation exponent m difficult
M. Fleury et al., Caprock and gas shale characterization: appropriate 3 petrophyscial methods
4. Energies nouvelles, Rueil-Malmaison, France
NMR issues
Does NMR measure total porosity ?
Typical relaxation time of nanopores ?
Does T2 distribution indicate pore size
distribution ?
Pore coupling effect
Fluid typing
Methane signature: adsorbed / free gas
Organic matter signature
T2 distribution alone insufficient
2 approaches:
Use diffusion contrast: T2-D maps
Use T1-T2 contrast: T1-T2 map
4
8. Energies nouvelles, Rueil-Malmaison, France
Fluid typing ?
From Glorioso et al. SPE 167785, 2014
Advanced techniques needed !
NMR signal
M. Fleury, Characterization of shales 8 with low field NMR
9. Energies nouvelles, Rueil-Malmaison, France
Outline
Relaxation of water in nanopores
Diffusion properties (cementation exponent
m)
Relaxation of methane in porous media
Relaxation of solid or pseudo-solid
components
Conclusion: fluid typing from T1-T2 map
9
10. Energies nouvelles, Rueil-Malmaison, France
10
102
101
100
10-1
10-2
10-3
10-4
Fast diffusion limit 4r2V/S << D
r2=10 mm/s
r2=1 mm/s
10-1 100 101 102 103 104
Pore size V/S (micron)
Measured T2 (ms)
T2b
Relaxation in nanopores
S
1 = r ´ + 1
T 2
V T Bulk
2
2
1 nm pore sizes
between
0.1 and 1ms
11. Energies nouvelles, Rueil-Malmaison, France
11
Example: caprock sample (COx)
T2 (ms)
(ms)
T
1
101
100
10-1
10-2
Hydroxyls
1
12
2
Mobile water
10-2 10-1 100 101
(23 MHz NMR instrument
18 mm probe)
12. Study of nanopores in clays
Energies nouvelles, Rueil-Malmaison, France M. Fleury et al., Characterization of interlayer water in clays using low field relaxation and nutation 12 experiments
from Porion et al. J. Phys. Chem. 2007
interlayer spacing
<1nm
Cristal with
hydroxyls
Counter-ions
and water
d001
(SAXS)
13. Energies nouvelles, Rueil-Malmaison, France
13
Example: smectite powder at RH=50%
101
T2 below 0.1 ms should not
be included in porosity
T1 (ms) 10-2 10-1 100 101
T2 (ms)
100
10-1
T1/T2=1
2.5
10
Hydroxyls
Mobile water
Mobile water
(23 MHz NMR instrument
10 mm probe)
Fleury et al., J. Phys. Chem. 2013
14. Energies nouvelles, Rueil-Malmaison, France
T2 in nanopores (smectite powders)
Fleury et al., J. Phys. Chem. 2013
M. Fleury, Characterization of shales 14 with low field NMR
16. Energies nouvelles, Rueil-Malmaison, France
Measurement of cementation m
Tortuosity from
resistivity (Archie)
diffusivity
16
= Fm-1
eff
D
m
D
m
R0 = F
w R
Classical method
Need knowledge of
water salinity
From NMR diffusion
Experiments at Sw=1
No specific knowledge
Some potential issues related to
clay conductivity
17. Energies nouvelles, Rueil-Malmaison, France
17
NMR method: deuterium diffusion
Example: Kw=50 nD, f: 6.4 %, size: D=L=15mm
100
80
60
40
20
0
t=0
2.6 hr
H2 outside
sample
10-2 10-1 100 101 102 103
T2 (ms)
A(T2) (a.u.)
16 hr
H2 not exchanged with D2
D2O
ö
æ
C C
* 6 1 exp
= -
2 2
k D t
H2O saturated
sample at t=0
å¥
=
-
f
0 5 10 15 20
0.8
0.6
0.4
0.2
0
-0.2
Time (hr)
C*
Dp=2.48e-006 cm2/s
Diffusion coefficient
m=1.87
÷ ÷
ø
ç ç
è
-
=
1
2
2 2
k
p
i f
r
C C k
C
p
p
Fleury et al., Energy Procedia 2009
Berne et al. , OGST, 2009
19. Energies nouvelles, Rueil-Malmaison, France
Water diffusivity: consequences
Diffusion length much larger than pore size :
D~ 10-10 m2/s, LD=(6Dt)1/2 ~800 nm at t=1ms
Pore sizes <500 nm are in a pore coupling
regime
19
MICP
Difficult to reconcile MICP and NMR !!
20. Energies nouvelles, Rueil-Malmaison, France
Relaxation of methane in porous media
Fundamental mechanisms known
Bulk properties (Oosting et al. 1971): spin rotation
Riehl et al. 1972, NMR relaxation of adsorbed
methane: anisotropic rotationnal motions at the
solid surface
large T1/T2 ratio
Existing work in petroleum sciences
Straley, 1997 T1/T2 ratio >> 1 even in partially
saturated samples
Recent work: Kausik et al. 2011, Rylander et al.
2013, Tinni et al. 2014….
20
21. Energies nouvelles, Rueil-Malmaison, France
Results for methane
Bulk CH4
200 bar
CH4 in
Shale
Sand
M. Fleury, Characterization of shales 21 with low field NMR
22. Energies nouvelles, Rueil-Malmaison, France
Results for methane in organic matter
100 bar 200 bar
M. Fleury, Characterization of shales 22 with low field NMR
23. Energies nouvelles, Rueil-Malmaison, France
Relaxation of solids or pseudo-solid
components
BPP theory
23
ù
úû
C t
1 2 é
2
t
= 2 2 2 2
1 1 4
êë
+
+
+
8
1
w t
w t
T
ù
úû
C t t
1 é
6 10
t
= + 2 2 2 2
2 1 4
êë
+
+
+
4
1
w t
w t
T
Liquids
Example:
Ice: T2=0.008 ms
T1=70 s at 30 MHz
24. Amplitude (a.u.)
Energies nouvelles, Rueil-Malmaison, France
Détection and quantification of hydroxyls
300
250
200
150
100
50
0
-50
Smectite 200°C
Cristal with
hydroxyls
Water
(removed
at 200°C)
10-2 10-1 100
Time (ms)
86% hydroxyls compared to XRD formulae:
Fleury et al., J. Phys. Chem. 2013
M. Fleury, Characterization of shales 24 with low field NMR
25. Energies nouvelles, Rueil-Malmaison, France
Detection of organic matter in coal
British coal
Anthracite
Vitrinite reflectance: 2.41
Specific density: 1.35
German coal
High volatile bituminous
Vitrinite reflectance: 0.79
Specific density: 1.71
M. Fleury, Characterization of shales 25 with low field NMR
26. Energies nouvelles, Rueil-Malmaison, France
Results: organic matter from shales (1/2)
Immature Oil window Gas window
Hydrogen content:
59 mg/g 30 mg/g 21 mg/g
M. Fleury, Characterization of shales 26 with low field NMR
27. Energies nouvelles, Rueil-Malmaison, France
Results: organic matter in shales (2/2)
« Dry » samples
Oil window Gas window
?
M. Fleury, Characterization of shales 27 with low field NMR
28. Principle of T1-T2 maps
103
102
101
100
10-1
T1/T2~2
liquids in porous media
T1/T2=1
bulk liquid
T1/T2~100
solid protons
Energies nouvelles, Rueil-Malmaison, France Réunion 28 du 15 novembre 2012
limit of confinement effect
T2 (ms)
T1 (ms)
resolution
limit
10-2
10-2 10-1 100 101 102 103
Pore size
protons mobility
low
high
small (1 nm) large
30. Energies nouvelles, Rueil-Malmaison, France
30
Conclusions
Fluid typing from T1-T2 maps
T2 not smaller than 0.1 ms for water in nanopores
Hydroxyls are below 0.1 ms, should be removed for
porosity calculation
Methane has a large T1 signature (1s)
Weak overlapping of the different protons
populations in a T1-T2 map
T1-T2 signatures well understood from existing
work and NMR theory