Download Experimental study of CO2-saturated water ‒ illite/kaolinite

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Energy Procedia 00 (2017) 000–000
www.elsevier.com/locate/procedia
13th International Conference on Greenhouse Gas Control Technologies, GHGT-13, 14-18
November 2016, Lausanne, Switzerland
Experimental study of CO2-saturated water ‒
illite/kaolinite/montmorillonite system at 70-80 °C, 100-105 bar
Eszter Sendulaa*, György Falusb, Mariann Pálesa, Barbara Péter Szabóc, Beatrix
Udvardib, István Kovácsb, Péter Kónyab, Ágnes Freilerb, Anikó Besnyib, Csilla Királya,
Edit Székelyc, Csaba Szabóa
Lithosphere Fluid Research Lab, Eötvös University, Pázmány Péter sétány 1/C, Budapest, H-1117, Hungary
b
Geological and Geophysical Institute of Hungary, Stefánia str. 14, Budapest, H-1143, Hungary
C
Department of Chemical and Environmental Process Engineering, Budapest University of Technology and Economics, Budafoki út 8.,
Budapest, H-1111, Hungary
a
Abstract
Low permeability caprock prevents migration of injected CO2 towards the surface and potable water reservoirs. As a result of
geochemical reactions among caprock minerals and CO2-saturated pore water, physical properties such as porosity, permeability
and tortuosity may change, which could affect the sealing capability of caprocks. Due to the common high clay mineral content
of caprocks, the reactivity of these minerals should be well-studied at CO2-saturated reservoir conditions. The main aim of this
study is to understand better the geochemical behavior of CO2–brine–clay mineral system by using laboratory experiments at
reservoir conditions on reference clays.
© 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the organizing committee of GHGT-13.
Keywords: CO2-clay interaction, carbon sequestration, lab experiment
1. Introduction
CO2 injection into the subsurface is considered to be an effective way to reduce emission of anthropogenic CO 2
into the atmosphere [e.g. 1-4], besides, CO2 is also used in the oil and gas industry as a working fluid for enhanced
oil and gas recovery (CO2-EOR and CO2-EGR) [e.g. 5, 6] and ultimately proposed as a possible fracturing fluid for
shale gas production [7]. Since the injected supercritical CO2 (scCO2) is less dense than the formation water,
buoyancy forces push it to migrate upwards, therefore, caprocks are important physical barriers to hinder the vertical
migration of CO2 towards the surface. For this reason, the sealing capacity of the caprock is crucial in the
1876-6102 © 2017 The Authors. Published by Elsevier Ltd.
Peer-review under responsibility of the organizing committee of GHGT-13.
2
Author name / Energy Procedia 00 (2017) 000–000
evaluation and planning of a potential CO2 storage reservoir or CO2-EOR project, to ensure that CO2 does not
escape into overlying shallow rock units, especially drinking water aquifers [8]. The overlying caprock likely will
be exposed to two phase (aqueous brine + variously hydrated scCO 2) or one phase fluid (aqueous brine containing
dissolved CO2). Consequently, modeling and experimental studies should focus on the effects of mineral reactivity
in both environments.
Caprocks are typically fine-textured shales, mudstones, or carbonate rocks with low permeability for any fluid,
therefore, flow rates across them can be very slow even at large pressure gradients. More importantly, the small
pore spaces have very high capillary entry pressures, which cause the caprock to act as a membrane that allows
water to pass but blocks scCO2 unless its pressure exceeds the capillary entry pressure [4]. In a properly-designed
CO2 storage site, the supercritical CO2 should not overcome this barrier, therefore, CO 2 percolation into the
originally water-wet caprock is relatively easier with molecular diffusion, or as a dissolved constituent in the brine
[8]. The dissolution of CO2 into the porewater will decrease its pH, thereby enhancing the dissolution of the porous
matrix. It has been described from the study of natural CO 2 occurrences that CO2-saturated brine could react with
the caprock in geological timescale causing mineral dissolution and precipitation within the caprock [9, 10], even
though CO2 leakage is not observed in a system currently. Considering that various types of clay minerals (e.g.
illite, montmorillonite, kaolinite, chlorite and glauconite) are common constituents of caprocks, their reaction
behavior with variously hydrated scCO2 and CO2-saturated porewater should be well studied.
Over the last few years increasing number of experimental studies has been published regarding the reaction of
clay minerals (mostly montmorillonite) and variously hydrated scCO 2. Several papers reported that scCO2 can be
intercalated in the montmorillonite’s interlayer space [e.g. 11-16] resulting in expansion of the mineral structure, and
therefore, promoting the self-sealing of caprock fractures. However, it has been also shown that depending on the
hydration state of scCO2, it can cause shrinkage of the montmorillonite [12, 13], which can lead to the reduction of
sealing integrity of the caprock. The volume change of montmorillonite modifies the pore structure of the caprock
and affects its porosity and permeability. As mentioned above, variously hydrated scCO 2 should not reach the
capillary entry pressure of the caprock, therefore, these experimental studies are mostly relevant only for minor
volume of the caprock (i.e. at the interface of the reservoir and the caprock, or along the walls of fractures and faults
within the caprock, where scCO2 can move by advection). The major part of the caprock is likely filled with CO2saturated or undersaturated porewater [8]. Some of the papers provide examples for modeling studies for caprockCO2 interactions [17-22] and some experimental works exist on the behavior of bulk caprock samples from different
locations with CO2-saturated porewater [e.g. 21, 23-27]. However, at least to our best knowledge, only few articles
have been published investigating the reaction between clay minerals and CO2-saturated water [e.g. 23, 28].
Hence, the main goal of this study is filling an existing gap in experimental studies in order to understand better
the geochemical behavior of CO2-saturated water–clay mineral system. For this reason, approximately 100 hours
long laboratory experiments were carried out under reservoir conditions relevant to geological CO 2 storage (70-80
°C, 100-105 bar) using mixtures of illite (IMt-1), kaolinite (KGa-1b) and Na-montmorillonite (SWy-2) reference
clays. The resulting solid phases were examined by Attenuated Total Reflectance Fourier Transform Infrared
Spectroscopy (ATR-FTIR) and X-ray powder diffraction (XRD), whereas the fluid compositions were measured by
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). For comparison, ‘as-shipped’ samples and
control samples exposed to chemically inert argon (Ar) at the same pressure-temperature conditions were also
studied the same way as the CO2-exposed samples.
2. Materials and methods
2.1. Clay samples
In this study we used illite (IMt-1, Silver Hill, Montana, USA), kaolinite (KGa-1b, Coss-Hodges pit, Washington
County, Georgia, USA) and Na-montmorillonite (SWy-2, Crook County, Wyoming, USA) reference clays from the
Source Clays Repository of The Clay Minerals Society. These reference clays have been previously well
characterized by Van Olphen and Fripiat [29], Chipera and Bish [30], Madejová and Komadel [31], Mermut and
Cano [32], Kogel and Lewis [33] and Mermut and Lagaly [34]. Since each of these clay minerals have different
crystal structure and chemistry, they are expected to react differently with CO2-saturated porewater. The mineral
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composition of the reference clays was reported by Chipera and Bish [30] for KGa-1b [~96 % kaolinite and trace
dickite, 3% anatase, 1% crandallite + quartz(?)] and for SWy-2 [~75% montmorillonite, 8% quartz, 16% feldspar,
1% gypsum + mica and/or illite + kaolinite(?) and/or chlorite(?)] and by Köster [35] for IMt-1 [mostly illite, trace of
quartz/rutile/anatase, 0.98% calcite]. In the experiments we used 1:1 weight ratio mixtures of the above mentioned
reference clays (IMt-1 + KGa-1b, SWy-2 + IMt-1, SWy-2 + KGa-1b).
2.2. Experimental setup
The experiments were carried out under reservoir conditions typical for the Pannonian Basin (70-80 °C, 100-105
bar) at the Department of Chemical and Environmental Process Engineering, Budapest University of Technology
and Economics, Hungary. The mixture of ultra-pure distilled-deionized water and powdered-mixed (1:1 mass ratio
mixtures) reference clays (illite-montmorillonite, kaolinite-montmorillonite, illite-kaolinite) was treated by CO2.
Control experiments were run simultaneously at the same temperature and pressure using Ar, which is considered to
be a non-reactive gas. Two stainless steel autoclaves with 37 ml inner volume were used in parallel, i.e. one for CO 2
experiments and one for reference CO2-free (Ar-treated) experiments (Fig. 1). Table 1 summarizes the water-rock
ratios, the experimental conditions (p, T, duration) and the used gases (CO2 or Ar) in the experiments. The duration
of each experiment was approximately 100 hours, therefore, to speed up the chemical reactions in this limited time
interval, we artificially increased the surface area by powdering the clay samples. High water-rock ratio was applied
(14-19) to facilitate the brine sampling and analyses. The clay particles were maintained in suspension by
continuous stirring which provided a higher reactive surface area to the clay minerals, since it prevented the
deposition of the particles. Moreover, stirring is likely to have reduced the diffusion control of the fastest reaction in
the solutions surrounding the mineral grains. Minor changes in temperature and pressure were observed during the
experiments, the latter likely due to minor loss of CO 2 and Ar from batch reactor and/or the uptake of CO 2 in
reactions. The reacted solid phases were examined by XRD and ATR-FTIR and the fluid samples collected during
the experiments were measured by ICP-OES. Ar-treated control samples and ‘as shipped’ samples were examined
the same way as the CO2-exposed samples.
2.3. X-ray powder diffraction (XRD)
Semi-quantitative XRD analyses were conducted at the Geological and Geophysical Institute of Hungary with a
Phillips® PW 1730 diffractometer (Cu cathode, 40 kV accelerating voltage and 30 mA tube-current, graphite
monochromator, goniometer speed 2°2θ/minute) to determine the mineral abundances in the ‘as shipped’, the CO2treated and the Ar-treated samples. All samples were analyzed in random orientation. The semi-quantitative
assessment of the relative concentrations of phases was performed by relative intensity ratios and half width of
specific reflections of minerals by using XDB Powder Diffraction Phase Analytical software 2.7.
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Fig. 1. Experimental setup used in the laboratory experiments. The numbers are: 1) ISCO pump, 2) control valve, 3) reactor inner space, 4)
manometer, 5) thermometer, 6a) thermostating fluid inlet, 6b) thermostating fluid output, 7) magnetic stirrer, 8) stirring core, 9) filter, 10) control
valve, 11) sampling vial.
Table 1. Summary of the experimental conditions (p, T, duration), weight of clay mixtures and pure water, water-rock ratios and the used gas
(CO2 or Ar) in each experiment.
Mixed reference clays
Sample
name
Gas
used
Weight of
clay mixtures
(g)
Weight of
pure water
(g)
Water-rock
ratio
Temperature
(°C)
Pressure
(bar)
SWy-2 + KGa-1b
SK8K
CO2
0.8165
14.9964
18.4
79.1 ± 1.2
102.5 ± 1.2
SWy-2 + KGa-1b
SK12K
Ar
0.8357
14.1752
17.0
81.4 ± 0.7
105.0 ± 1.6
IMt-1 + SWy-2
IS10K
CO2
0.8595
13.4515
15.7
81.4 ± 0.9
104.7 ± 1.0
IMt-1 + SWy-2
IS11K
Ar
0.9466
13.7936
14.6
70.4 ± 7.1
103.2 ± 2.8
IMt-1 + KGa-1b
IK9K
CO2
0.8023
15.1472
18.9
72.4 ± 8.8
101.9 ± 7.3
IMt-1 + KGa-1b
IK13K
Ar
0.8140
15.1261
18.6
82.4 ± 1.6
100.2 ± 8.9
2.4. Attenuated Total Reflectance Fourier Infrared Spectroscopy (ATR-FTIR)
The powdered and mixed clay samples were measured before and after CO2/Ar treatment by ATR-FTIR at the
Geological and Geophysical Institute of Hungary. This method is highly sensitive to the OH --bearing phases,
therefore beneficial for the study of clay minerals. The instrument is a Bruker Vertex 70 spectrometer with a single
reflection ATR cell (Bruker Platinum diamond ATR) and an MCT detector (mercury-cadmium-telluride). This
instrument was utilized to acquire ATR spectra in the mid–infrared spectral range (400–4000 cm–1) with 64 scans
and a resolution of 4 cm-1. The samples were dried at least for 30 minutes at 80°C in an oven right before the
measurements in order to remove the majority of adsorbed water, which significantly facilitates the interpretation of
the spectra. Tóth et al. [36] showed that the relatively low temperature of the heat treatment does not cause any first
order alterations in the clay mineral structures. Furthermore, since the experiments themselves were carried out at
70-80 °C, we do not expect significant alterations due to our sample preparation process. The mixed and powdered
clay sample was placed on the diamond ATR crystal and pressed with a compression clamp and was analyzed. The
analysis was repeated 3 to 5 times and the measured IR spectra were averaged after atmospheric compensation and
ATR correction. In some cases, quick re-adsorption of water from the atmosphere was experienced on
montmorillonite-bearing mixtures. In these cases, we used the average spectrum of the first two spectra only where
the effect of re-adsorption was not significant. ATR correction was necessary since the light penetration depth into
the sample is a function of the IR radiation’s wavelength, refractive indices of the sample and the ATR crystal [37].
The ATR correction was carried out taking into account 1.56 mean reflection index of the samples, single reflection
in the ATR crystal and 45° incidence angle. The baseline was corrected by the automatic algorithm of OPUS 7.2
software (concave rubber band correction, 1 or 2 iterations, 64 numbers of baseline points). For the spectral region
of 1730-1330 cm-1 baseline correction was carried out separately and then the spectra were smoothed (15 smoothing
points). As all the spectra were recorded under identical experimental conditions, the intensity and wavenumber of
the characteristic infrared bands depend only on the particle size, degree of crystallinity, crystallographic anisotropy
and the chemical composition of the samples.
2.5. Inductively coupled plasma optical emission spectroscopy (ICP-OES)
Fluid samples collected at several time steps during and right after both CO2 and CO2-free control (Ar)
experiments were analyzed by ICP-OES, HORIBA Jobin Yvon® ULTIMA 2C at the Geological and Geophysical
Institute of Hungary to determine the Na +, K+, Ca2+, Mg2+, Mn2+, Al3+, H2SiO3(aq) and Fe(total) concentrations. It
should be noted here that the results of ICP-OES should be treated with caution, since only small volume of fluid
samples could be taken during the experiments (0.1-0.8 ml at each sampling period) despite of the high water/solid
ratio (14-19, Table 1). These amounts were not enough for the measurements that required 5 ml fluid sample,
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therefore the samples were diluted by the factor of 6-33 (Appendix A), resulting in an increased analytical error.
Noted however, that any appearance of the above mentioned elements in the fluid samples suggest chemical reaction
in the clay-water-CO2/Ar system, since distilled and deionized water was used as initial fluid. In some cases, where
it was possible, duplicate samples were taken and analyzed to ensure the quality of the data.
3. Results
3.1. XRD
Mineral composition of the mixtures of the ‘as shipped’ reference clays and the CO2/Ar-treated samples were
characterized by bulk XRD analysis (Table 2) to detect the changes in the mineralogy as a result of the experiments.
All original, non-treated clay mixtures show the presence of quartz, K-feldspar and some amorphous phases.
Kaolinite and minor amount of anatase detected in the mixtures containing KGa-1b reference clay. The SWy-2
bearing mixtures contain montmorillonite, 2-3% calcite and minor amount of mica and/or illite. Additionally, illite
detected in the IMt-1 bearing mixtures (Table 2).
The resulting solid phases from the experiments were measured after drying the samples at ambient conditions.
In the CO2-exposed illite-kaolinite mixture (IK9K), slight decrease of the illite peak was detected, whereas, no
significant changes were observed after Ar-treatment (IK13K) (Table 2, Fig. 2). In the montmorillonite-bearing
samples the lack of the initially present calcite was observed as a result of CO 2-treatment, while in the Ar-treated
montmorillonite-illite mixture (IS11K) trace amount of calcite was still recognized even after the experiment (Table
2, Fig. 2). Furthermore, shift of the initial d001 spacing of the montmorillonite peak were experienced by about 2 Å
(from ~13 Å to ~15 Å) in the case of both CO 2 and Ar-treated samples, together with the increase of the peak
intensity (Table 2, Fig. 2).
3.2. ATR-FTIR
Infrared spectroscopy has been used to characterize clay minerals both in the ‘as shipped’ and CO 2/Ar-treated
samples, since the specific absorption bands of structural OH - and Si–O groups play an important role in the
differentiation of clay minerals from each other [38]. All bands presented here were characterized according to data
from Madejová and Komadel [31], Madejová [38], Tóth et al. [36], Krukowski et al. [15] and Kovács et al. [39].
Kaolinite was identified by the four absorption bands in the OH - stretching region (strong bands around 3620 and
3695 cm-1 and weak absorptions around 3669 and 3653 cm-1) [38]. Illite and montmorillonite show a single band at
3620 cm-1 corresponding to the hydroxyl group at the aluminum-enriched octahedral positions. Furthermore, related
to montmorillonites, a broad band around 3400 cm-1 is usually observed corresponding to the H-O-H vibration of
mainly interlayer water with a decreasing shoulder near 3240 cm-1 representing an overtone of bending mode of
molecular water. A band at ~1630 cm-1 also appears related to the OH- bending mode of molecular water.
d001 reflection
of
montmorillonite
Amorphous
Anatase
Calcite
Plagioclase
K-feldspar
Quartz
Kaolinite
Mica
Gas used
Illite
Sample name
Montmorillonite
Table 2. Mineralogical composition of the samples and position of the d001 reflection of montmorillonite before and after experiments by semiquantitative XRD analyses.
Å
%
SWy-2 + KGa-1b -
35
-
3
50
6
1
-
2
1
2
13.049
SK8K
CO2
39
-
2
49
2
1
1
-
1
5
14.546
SK12K
Ar
32
-
2
57
4
2
1
-
1
1
15.137
IMt-1 + SWy-2
-
33
44
-
-
11
5
-
3
-
4
12.807
6
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IS10K
CO2
65
26
-
-
4
2
-
-
-
3
14.998
IS11K
Ar
41
46
-
-
6
3
-
1
-
3
14.437
IMt-1 + KGa-1b
-
-
30
-
62
3
2
-
-
1
2
-
IK9K
CO2
-
21
-
56
11
2
-
-
1
9
-
IK13K
Ar
-
27
-
66
3
1
-
-
1
2
-
Fig. 2. The figure shows XRD patterns obtained from non-treated (blue), CO2-treated (green) and Ar-treated (purple) mixtures of
montmorillonite-illite, illite-kaolinite and montmorillonite-kaolinite after drying the samples at ambient conditions. The position of d001
reflection of montmorillonite (m, shaded) is increased by ~2Å as a result of the experiments. Abbreviations: m-montmorillonite, i-illite, kkaolinite, q-quartz, f-feldspar, c-calcite.
The 1300-400 cm-1 range is characteristic for the stretching and bending vibrations of Si-O and Al-O and bending
of OH-. The strong band near 1000 cm-1 is due to Si–O–Si stretching vibrations, while the band at 1116 cm-1 refers
to the Si-O stretching (longitudinal mode). The Al-Al-OH bending bands of kaolinite appear at 914 and 936 cm-1.
The bands at 795 cm-1 and 778 cm-1 are corresponding to quartz and the band at 751 cm-1 is related to the
perpendicular stretching of Si-O.
The ATR-FTIR spectrum of the CO2-treated illite-kaolinite mixture (IK9K) shows relative decrease of band
intensities compared to the non-treated clay mixtures at 3695 cm-1 and around 1430 cm-1 corresponding to OHstretching in kaolinite structure and vibration of CO32- in carbonates, respectively (Fig. 3). The intensity of bands
increased at 1630 cm-1 related to OH- bending and at 1001 cm-1 and 1026 cm-1 in the Si–O–Si stretching vibration
region. In the Ar-treated sample (IK13K) no remarkable changes were observed in the 1700-1300 cm-1 region
where the bands of carbonates and molecular water appear. However, the intensity of bands decreased both in the
OH- stretching region related to kaolinite and at 1001 cm-1 and 1026 cm-1 assigned to Si–O–Si stretching. No
significant shift was observed in the peak positions, except in the band around 1630 cm-1 related to the bending
mode of molecular water. The position of this band shifted from the original 1643 cm-1 to 1639 cm-1 in the case of
the Ar-treated sample (IK13K) and to 1635 cm-1 in the CO2-treated sample (IK9K).
In comparison, in the CO2-treated montmorillonite-kaolinite mixture (SK8K) relative increase of the bands
around 3400 cm-1, 1630 cm-1, 1430 cm-1 and decrease at 1001 cm-1, 1026 cm-1 and between 3620 cm-1 and 3659 cm-1
were observed (Fig. 3). Moreover, the absorbance at 3620 cm-1 associated with both kaolinite and montmorillonite
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relatively increased compared to the band intensity at 3659 cm-1 related to kaolinite only. Contrary, in the Artreated sample (SK12K) the band intensities in the OH- stretching region did not change significantly, while in the
Si–O–Si region increased. No significant changes were observed in the 1700-1300 cm-1 region and around 3400 cm1
.
In the CO2-treated montmorillonite-illite mixture (IS10K), the relative intensity of the bands increased in both the
OH- stretching and Si–O–Si stretching regions (Fig. 3). The only band that decreased around 1430 cm-1 is related to
the vibration of CO32-. In the Ar-treated montmorillonite-illite mixture (IS11K) the band related to structural OHvibration at 3620 cm-1 decreased. Bands associated with molecular water around 3400 cm-1 and at 1630 cm-1, and
the peak intensities in the Si–O–Si stretching vibrations band around 990-996 cm-1 did not change significantly. The
CO32- peak at 1430 cm-1 slightly increased.
3.3. Fluid composition
Fluid samples were taken at regular time intervals (1, 20-27, 43-48 and 94-98 hours after the start and right after
the end of the experiments) to investigate fluid chemistry development as a function of time of exposure to CO 2saturated water. The results of fluid sample analysis taken during and after CO 2-free (Ar) and CO2 experiments are
summarized on Fig. 4 and in Appendix A. It must be noted that in the case of the last sampling (after 95, 97, 98
hours), mineral precipitation due to the reactor depressurization and cooling could potentially modify the solution
compositions compared to original experimental conditions. Since the starting solution was ultra-pure water
(distilled and deionized), presence of any measured cations (Na +, K+, Ca2+, Mg2+, Mn2+, Al3+, H2SiO3(aq) and Fe(total))
in the resulting solution is due to geochemical reactions in the fluid-clay mineral-CO2/Ar system. Note that the
concentration of Al3+ and Fe(total) were below the detection limit and K+ concentration was measured with relatively
high uncertainty (±20%) in most cases (Appendix A). Argon gas is assumed to be inert, therefore, changes in the
solution composition in the case of Ar-treated samples is expected to be driven by the pressure and temperature of
the system and initial disequilibrium between the solid sample and pure water. Compared to the reference data of
the chemically inert Ar, the differences in the CO2-exposed cases assumed to be the effect of CO2.
8
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Fig. 3. Average ATR-FTIR spectra of the mixed clay samples are shown before (blue) and after treatment with CO2 (green) and Ar (purple).
Standard deviance of the spectra indicated with dashed lines. In the 3800-3000 cm-1 region, the labelled bands correspond to: O-H stretching of
inner surface hydroxyl group in kaolinite (3690 cm-1), O-H stretching of inner hydroxyl group in kaolinite (3621 cm-1), O-H stretching of
hydroxyl group at the aluminum-enriched octahedral positions in mixtures containing montmorillonite and illite (3623 cm-1), H-O-H asymmetric
and symmetric stretching associated with interlayer water related mostly to montmorillonite (around 3400 cm-1), H-O-H 2ν2 bending overtone
mode (3240 cm-1). In the 1730-1330 cm-1 region the bands are related to: H-O-H bending mode of molecular water (1640-1630 cm-1) and
vibration of CO32- (1430 cm-1). In the 1300-500 cm-1 region the bands correspond to: longitudinal Si-O stretching (1116 cm-1), in-plane Si-O
stretching (1026 cm-1, 1001 cm-1 and 996-990 cm-1), O-H stretching of inner surface hydroxyl group in kaolinite (940 cm-1), Al-Al-OH
deformation (914-908 cm-1), quartz (795 cm-1 and 778 cm-1) and perpendicular stretching of Si-O (751 cm-1) [15, 31, 36, 38, 39].
Fig. 4. ICP-OES results of the fluid samples were collected at several time steps during the experiments with CO2 and Ar. Squares show the
results of montmorillonite-kaolinite mixtures, circles represents the illite-kaolinite mixtures and hexagons indicates the mixture of
montmorillonite-illite. Error bars indicate uncertainties of the measurements. The last sampling can potentially represents modified solution
composition due to mineral precipitation because of the reactor depressurization and cooling.
Cations (Ca2+, Mg2+, Mn2+, K+, Na+) and H2SiO3(aq) previously absent in the starting solution, appeared in all CO2
experiments already 1 hour after the start of the experiment indicating fast dissolution of reacting solids (Fig. 4).
Further increase of the cation concentrations during the CO2 experiments was not clear.
In the CO2-free (Ar) experiments Ca2+ and Mn2+ concentration of the resulting fluid samples was around the
detection limit of ICP-OES. Furthermore, the concentration of Mn2+, K+, Na+ and H2SiO3(aq) were significantly
lower than in the experiments with CO2. The only exception is the illite-kaolinite mixture, where the Na+
concentration was higher in the Ar-treated sample (IK13K). Slight increase in the concentration of Mg2+, K+, Na+
Author name / Energy Procedia 00 (2017) 000–000
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and H2SiO3(aq) was detected during the Ar-treated control experiments (Fig. 4), which suggests a slower reaction rate
at the same pressure-temperature conditions than in the CO2-exposed case.
4. Discussion
4.1. The relevance of CO2-staurated water‒clay system in CO2 geological storage
Following the early study of Fripiat et al. [40] on the interlamellar adsorption of CO2 by smectites at low
temperature, in the last few years several experimental works have been published on the behavior of
montmorillonites with variably hydrated (from dry to H2O-saturated) scCO2 fluids under the conditions relevant to
CO2 geological storage [e.g. 12-16, 41-44]. The focus of these studies was on the intercalation of CO 2 into the
interlayer region of montmorillonite and volume change due to swelling or contraction of the clay mineral structure
as a function of the initial hydration state of montmorillonite and water saturation of scCO 2. Corresponding to the
intercalation of 0, 1, 2 or 3 planes of H2O molecules in the interlayer region, the hydration state of montmorillonite
typically referred to as 0W (dehydrated), 1W (monohydrated), 2W (bihydrated) or 3W (trihydrated), however, these
hydration states usually coexist due to structural heterogeneities [45].
The CO2 intercalation into montmorillonite under geological storage conditions was suggested based on the
expansion of CO2 exposed montmorillonite measured by XRD [11-13]. However, the first direct evidence of CO2
intercalation was provided by Loring et al. [41] using Ca-STx-1 montmorillonite with ~1W initial hydration state
and the combination of in-situ XRD, MAS-NMR and ATR-IR techniques. For Na-montmorillonite, Loring et al.
[14] showed that CO2 intercalation is maximal from ~0W to 1W initial hydration states, and decreases with further
hydration of the montmorillonite. Under geological storage conditions (up to a few km depth) montmorillonites are
believed to be stable mostly between 0W and 1W hydration state, while at shallower reservoir environments 3W
hydration state could be also in equilibrium [46]. It was shown that uncompacted Na-montmorillonite can swell up
by 9% when exposed to high purity CO2 [11], however Jong et al. [44] measured only ≤3% swelling strain on
compacted samples at similar experimental conditions. Schaef et al. [16] extended the experiments to Ca- and Mgsaturated montmorillonites, giving an upper limit on the capacity of clays to sequester CO 2. Ilton et al. [13] and
Schaef et al. [12] found evidence for partial dehydration of Na + and Ca2+ exchanged montmorillonite with ≥2W
initial hydration states exposed to wet scCO2, however Ilton et al. [13] showed that above ~65% H2O saturation in
scCO2 the sub-3W montmorillonite swelled up to 3W hydration state. Both hydration and dehydration processes
can be rapid and take place in few seconds-few hours [13, 15, 44]. Only few papers studied illite and kaolinite
behavior in scCO2 environment. Kaolinite is used often in several experiments as a control sample, since it is
typically regarded as non-expandable clay mineral [e.g. 14] which is also inert to chemical degradation by carbonic
acid [e.g. 43].
All the above mentioned articles studied the clay-scCO2 system with variable H2O saturation, however, to our
best knowledge, only very few experimental studies focus on the clay mineral‒CO2-saturated water system [e.g. 28,
43], which could be relevant at longer time scales and further away from the injection well. Depending on the CO 2
injection rate, the reservoir permeability and thickness, the distance from the injection point of CO2 to the caprock
and the plume velocity, the time required to the CO 2 plume to reach the base of the caprock can vary. Since the
water uptake of scCO2 can be very fast, scCO2 can reach saturation in H2O if enough water is accessible in the pore
space. If the scCO2 reaches 100% water saturation at the given temperature and pressure conditions,
montmorillonite could only swell based on the work of Ilton et al. [13], however, in case of lower H2O saturation of
scCO2 shrinkage of montmorillonites can occur at the bottom of the caprock. Volume change of the
montmorillonites in the caprock can cause porosity and permeability change and therefore can affect the capillary
entry pressure of CO2 into the caprock during the injection period. Since in a properly-designed injection site,
injected CO2 pressure should not reach the capillary entry pressure of the caprock to avoid leakage of the storage
system, CO2-saturated water is more likely to enter into the caprock through diffusion [8]. Therefore, reaction
between clay minerals and CO2-saturated porewater is more likely in the caprock, whereas variously hydrated scCO2
possibly can react with the caprock only on the reservoir-caprock interface, or in the fractures where the scCO 2 can
move by advection.
10
Author name / Energy Procedia 00 (2017) 000–000
4.2. Discussion of experimental results
4.2.1. Illite-kaolinite mixture
In the case of illite-kaolinite mixture, XRD measurements suggest the dissolution of illite in the CO 2 experiment
relative to the other phases (IK9K), and no significant changes in the Ar-treated sample (IK13K). The higher extent
of the dissolution of illite-kaolinite mixture in the CO2 exposed experiment confirmed by the ICP-OES results. The
concentration of dissolved Ca 2+, Mg2+, Mn2+, K+, Na+ and H2SiO3(aq) increased in the fluid samples compared to the
initial pure water. Minor dissolution in Ar-treated samples was also observed, however the concentration of K + and
H2SiO3(aq) were 2-3 times lower than in the CO2-treated case, and Ca2+, Mg2+ and Mn2+ concentration was under the
limit of detection. The increased Ca2+, Mg2+, Mn2+ content of the CO2-treated fluid sample is indicating the
dissolution of carbonates initially present in the IMt-1 reference clay [35]. Carbonate dissolution is supported by
ATR-FTIR spectrum, where decrease of the peak intensity around 1430 cm-1 was observed associated to CO32- in
carbonates (IK9K). The higher K+ and H2SiO3(aq) concentration of the fluid samples in the CO2-treated case
suggests that presence of CO2 enhanced the decomposition of clay minerals in the mixture. This result is in
agreement with the experiment of Galán and Aparicio [43], who reported minor decomposition of illite indicated by
the increased concentration of soluble elements (Si, Al, Na and K) after CO2 treatment with excess water.
Dissolution of K-feldspar could also contribute to the increase of K + and H2SiO3(aq) concentrations of the fluid
samples, however, only small amount was initially present in the samples. Interestingly, the Na+ concentration of
the fluid samples in the Ar-treated sample was four times higher than in the CO 2 exposed case, which might be the
result of artificial contamination of the sample.
4.2.2. Montmorillonite-bearing mixtures
In the case of montmorillonite-bearing samples, the shift of the initial d001 basal reflection by ~2 Å (from ~13 Å
to ~15 Å) on the XRD diffractograms suggests the expansion of the crystal structure. The expansion could be the
result of cation-exchange (e.g. replacement of monovalent Na+ by divalent Ca2+) and/or CO2 incorporation into the
interlayer or simply the changes in the hydration state of the montmorillonite (from 1W to 2W hydration state). In
order to understand the reason of d001 shift, we re-measured the illite-montmorillonite samples (IS10K and IS11K)
after the same preparation procedure that was applied before the ATR-FTIR measurements (drying it for 30 minutes
at 80°C in an oven). In this case, the previously experienced shift of the d001 montmorillonite peak was no longer
detected in the samples. At the same time, the increased intensity of the montmorillonite peak relative to the illite
peak remained recognizable in the CO2 exposed samples (IS10K), while disappeared in the Ar-treated samples
(IS11K) (Fig. 5). The result clearly shows that the relative increase in the amount of montmorillonite was the result
of reaction between the clay sample and CO2-saturated water.
ATR-FTIR spectra can be used to confirm if exchange of the interlayer cation occurred or not during the
experiments. According to Madejová [38] the position of the broad band of H-O-H stretching vibration on ATRFTIR spectra near 3400 cm-1 decreases in order K-Na-Ca-Mg interlayer cation, because of the increasing
polarization power of the interlayer cation due to the charge/radius relation. Since no shift was observed in the
position of this peak, cation exchange during the experiments is unlikely. It is unclear, whether CO2 incorporation
into the interlayer occurred or not. Michels et al. [47] showed on a dehydrated LiF-hectorite sample that intercalated
dry CO2 can desorb from the interlayer space upon heating and LiF-hectorite is able to retain the CO2 up to 35°C.
However, this threshold temperature is highly dependent on the type of interlayer cation and to our best knowledge,
there is no similar experiment on Na-or Ca-montmorillonite, therefore the threshold temperature for CO 2 desorption
is not known for these clay minerals. Nevertheless, it is unlikely that significant CO2 intercalation into the interlayer
could occur with the high water concentration used in our experiments (CO2-saturated water), since several previous
experimental and modeling studies showed even in the CO2-rich environments (variously hydrated scCO2) that CO2
intercalation decreases with increasing hydration of the montmorillonite [e.g. 14]. Therefore, the most likely
explanation is that the detected d001 shift on the XRD diffractograms is a result of the increased hydration state of
montmorillonite from 1W to 2W because of the experiments with high water content. The measured d001 values
for montmorillonite are in agreement with the values reported as a function of integral hydration states of 0W (9.7–
10.2 Å), 1W (11.6–12.9 Å), 2W (14.9–15.7 Å) and 3W (18.0–19.0 Å) at ambient conditions [45].
Author name / Energy Procedia 00 (2017) 000–000
11
In agreement with the XRD results, the relative increase of the bands around 3400 cm -1 and 1640-1630 cm-1
associated with interlayer water on ATR-FTIR spectra could indicate the increase of the relative amount of
montmorillonite in the samples, assuming that the hydration state of the montmorillonite was the same in all samples
after the heat-treatment in the oven. As both the XRD and FTIR spectra show proportional amount of the minerals
in the sample, this relative increase could be slightly influenced by the dissolution of other minerals in the mixture
(e.g. calcite or K-feldspar), however, this effect likely to be minor given the small initial amount of these minerals.
In addition, absorption strength on ATR-FTIR spectra is sensitive to the physical size of the particles [48-50],
therefore, increased absorbance of the CO2-treated samples may be the result of aggregation of montmorillonite
particles during the experiments.
Fig. 5. The figure shows XRD patterns obtained from CO2-treated and Ar-treated illite-montmorillonite samples (IS10K and IS11K) after drying
the samples at ambient conditions and at 80°C in oven for at least 30 minutes. Diffractogram of the ‘as shipped’ sample (blue) provided for
comparison. The position of d001 montmorillonite peak (m, shaded) is increased by ~2Å in the samples dried at ambient conditions after the
experiments compared to the ‘as shipped’ sample. However, no significant change was observed in the peak position after drying the same
samples in oven. Relative increase in the intensity of montmorillonite peak compared to the illite peak disappeared in the Ar-treated sample
(IS11K) after oven drying, but remained in the CO2-treated sample (IS10K) suggesting that relative amount of montmorillonite increased as a
result of CO2 treatment. Abbreviations: m-montmorillonite, i-illite, q-quartz, c-calcite.
Based on the results of ICP-OES (increased Ca2+, Mg2+ and Mn2+ concentration of the fluid samples) and XRD
measurements, dissolution of minor amount of calcite initially present in the samples is likely in the CO 2 exposed
cases, while there was no or only minor dissolution observed in Ar-treated samples. Since the cation concentration
of the CO2 exposed fluid samples was already increased at the very first fluid sampling after one hour and further
clearly increasing trend was not detected, rapid chemical reactions could be assumed. This is in agreement with
previous studies [e.g. 15] reporting fast equilibration of the system. Control experiments with Ar can support this
argument, since increasing concentration of cations could be detected until the end of the experiments, indicating
that the fast reaction kinetics was not caused by pressure and temperature but most likely related to CO 2.
12
Author name / Energy Procedia 00 (2017) 000–000
5. Conclusion
In this study, we conducted batch experiments at reservoir conditions suitable for CO2 sequestration to
understand the reaction of montmorillonite, kaolinite and illite with CO 2-saturated water. Control samples exposed
to chemically inert Ar were also studied as comparison.
The experimental results (XRD, ICP-OES) indicate rapid and total dissolution of originally present carbonates in
the CO2-treated samples. In the Ar-exposed control samples, carbonate dissolution was negligible at the same
pressure-temperature conditions.
The clay mixtures, initially containing montmorillonite, were more reactive than the sample of illite-kaolinite
mixture. In these reactive samples, both XRD and ATR-FTIR measurements suggest slight increase in the relative
amount of montmorillonite and/or aggregation as a result of CO2-treatment, while no remarkable changes were
observed in the Ar-treated samples compared to the ‘as shipped’ ones.
Expansion of the crystal structure of montmorillonite was observed on the XRD diffractograms after both CO 2
and Ar experiments. The reason is most likely the high water concentration we used in the experiments, which
caused change in hydration state of the montmorillonite from 1W to 2W. The effect of CO 2 intercalation or cation
exchange is very likely negligible.
In the fluid samples primary cation (Ca2+, Mg2+, Mn2+, K+, Na+) and H2SiO3(aq) concentration increased in the
CO2-exposed samples, however, no significant changes in Ca2+ and Mg2+ concentration were observed in Ar-treated
samples. Based on the fluid chemistry, fast dissolution of the CO2-treated samples and slower dissolution of Artreated samples were detected.
Acknowledgements
This research was carried out in agreement between Eötvös Loránd University and Hungarian Geological and
Geophysical Institute (TTK 2461/1/2013 and MFGI 206-114/2013) with partial financing by the Hungarian National
Research Fund (K 115927 to Gy. Falus). The project was partially supported through the New National Excellence
Program of the Ministry of Human Capacities, Hungary (ÚNKP-16 to Cs. Király). Work of E. Székely was
supported by the Hungarian Academy of Science by the János Bolyai Research Grant. This is the 84 publication of
Lithosphere Fluid Research Lab at Eötvös University.
Appendix A.
Appendix A. ICP-OES results of the fluid samples are collected at several time steps during the experiments. The results presented here are
corrected with the dilution factor indicated in the table, as well. The uncertainties are demonstrated by the type of numbers (bold numbers
indicate ±2%, regular numbers represent ±5% and italic numbers show ±20% analytical error, <LOD indicate concentrations below the limit of
detection). It must be noted that in the case of the last sampling (after 95, 97, 98 hours), mineral precipitation due to the reactor depressurization
and cooling can potentially change the solution compositions compared to original experimental conditions.
Sample
name
Gas
used
SK8K
CO2
SK12K
Ar
IS10K
CO2
IS11K
Ar
Duration
hours
1
20
43
95
2
27
48
1
26
48
97
1
Dilution factor
for the
measurements
15
24.9
13.1
10
14
11.8
16
14.1
6.35
19.95
6
12.3
Concentration (corrected with dilution)
2+
Mg
K+
Na+
42.2
37.8
24.0
34.8
<LOD
<LOD
<LOD
11.1
10.8
7.7
10.4
2.0
0.9
0.79
34.0
39.6
60.2
25.2
0.39
14.9
28.5
15.2
16.0
8.6
10.2
9.1
32.8
34.6
65.3
25.0
12.4
207.5
244.7
197.0
222.0
119.6
187.0
198.6
296.6
264.4
398.8
172.3
56.7
Ca
137.7
147.6
196.2
84.1
<LOD
2+
Fe(total)
mg/l
1.3
<LOD
<LOD
<LOD
3.9
1.2
<LOD
Mn2+
H2SiO3(aq)
Al3+
0.45
0.51
0.42
0.6
0.015
0.015
<LOD
<LOD
<LOD
<LOD
<LOD
0.042
0.04
0.12
<LOD
<LOD
1.3
1.8
2.2
1.3
<LOD
89.5
95.4
82.6
77.6
78.4
72.8
88.1
119.3
180.4
316.1
93.7
27.0
20.8
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
Author name / Energy Procedia 00 (2017) 000–000
IK9K
CO2
IK13K
Ar
26
97
1
20
43
94
95
2
26
98
31.25
10
12.375
14
12.5
12.1
10
12.5
11.7
10
<LOD
0.46
80.6
86.0
82.3
80.1
71.7
<LOD
<LOD
2.8
1.14
1.1
24.2
27.8
27.7
25.5
24.1
2.6
3.1
2.2
29.8
8.7
23.3
22.9
26.6
26.8
26.7
6.1
6.6
16.9
138.7
155.7
14.8
12.0
13.4
12.2
12.2
51.9
49.0
44.4
1.22
0.8
0.9
<LOD
<LOD
<LOD
<LOD
0.10
<LOD
<LOD
13
0.018
0.005
1.1
1.3
1.6
1.9
1.7
<LOD
<LOD
<LOD
64.8
113.4
57.0
89.2
93.4
91.2
75.9
15.6
40.0
49.8
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
<LOD
References
[1] Bachu S, Gunter WD, Perkins EH. Aquifer disposal of CO2: hydrodynamical and mineral trapping. Energ Convers Manage 1994; 35:264-279.
[2] Bachu S. Screening and ranking of sedimentary basins for sequestration of CO 2 in geological media in response to climate change. Environ
Geol 2003; 44:277-289.
[3] Holloway S. Underground sequestration of carbon dioxide — a viable greenhouse gas mitigation option. Energy 2005; 30:2318–2333.
[4] Benson SM, Cole DR. CO2 Sequestration in deep sedimentary formations. Elements 2008; 4:325–331.
[5] Oelkers EH, Cole DR. Carbon dioxide sequestration: A solution to a global problem. Elements 2008; 4:305–310.
[6] Godec M, Kuuskraa V, Van Leeuwen T, Melzer LS, Wildgust N. CO 2 storage in depleted oil fields: The worldwide potential for carbon
dioxide enhanced oil recovery. Energy Procedia 2011; 4:2162–2169.
[7] Middleton RS, Carey JW, Currier RP, Hyman JD, Kang Q, Karra S, Jiménez-Martínez J, Porter ML, Viswanathan HS. Shale gas and nonaqueous fracturing fluids: Opportunities and challenges for supercritical CO2. Appl Energ 2015; 147:500–509.
[8] Liu F, Lu P, Griffith C, Hedges SW, Soong Y, Hellevang H, Zhu C. CO 2–brine–caprock interaction: Reactivity experiments on Eau Claire
shale and a review of relevant literature. Int J Greenh Gas Con 2012; 7:153–167.
[9] Király C, Szamosfalvi Á, Zilahi-Sebess L, Kónya P, Kovács IJ, Sendula E, Szabó C, Falus G. Caprock analysis from the Mihályi-Répcelak
natural CO2 occurrence, Western Hungary. Environ Earth Sci 2016; 75:635.
[10] Kampman N, Busch A, Bertier P, Snippe J, Hangx S, Pipich V, Di Z, Rother G, Harrington JF, Evans JP, Maskell A, Chapman HJ, Bickle
MJ. Observational evidence confirms modelling of the long-term integrity of CO2-reservoir caprocks. Nat Commun 2016; 7:12268
[11] Giesting P, Guggenheim S, van Groos AFK, Busch A. Interaction of carbon dioxide with Na-exchanged montmorillonite at pressures to 640
bars: Implications for CO2 sequestration. Int J Greenh Gas Con 2012; 8:73-81.
[12] Schaef HT, Ilton ES, Qafoku O, Martin PF, Felmy AR, Rosso KM. In situ XRD study of Ca 2+-saturated montmorillonite (STX-1) exposed to
anhydrous and wet supercritical carbon dioxide. Int J Greenh Gas Con 2012; 6:220-229.
[13] Ilton ES, Schaef HT, Qafoku O, Rosso KM, Felmy AR. In situ X-ray diffraction study of Na+-saturated montmorillonite exposed to variably
wet super critical CO2. Environ Sci Technol 2012; 46:4241−4248.
[14] Loring JS, Ilton ES, Chen J, Thompson CJ, Martin PF, Bénézeth P, Rosso KM, Felmy AR, Schaef HT. In situ study of CO 2 and H2O
partitioning between Na−montmorillonite and variably wet supercritical carbon dioxide. Langmuir 2014; 30:6120−6128.
[15] Krukowski EG, Goodman A, Rother G, Ilton ES, Guthrie G, Bodnar RJ. FT-IR study of CO2 interaction with Na+ exchanged
montmorillonite. Appl Clay Sci 2015; 114:61–68.
[16] Schaef HT, Loring JS, Glezakou V-A, Miller QRS, Chen J, Owen AT, Lee M-S, Ilton ES, Felmy AR, McGrail BP, Thompson CJ.
Competitive sorption of CO2 and H2O in 2:1 layer phyllosilicates. Geochim Cosmochim Ac 2015; 161:248-257.
[17] Johnson JW, Nitao JJ, Morris JP. Reactive transport modeling of cap rock integrity during natural and engineered CO2 storage. In: Thomas
DC, Benson SM, editors. Carbon dioxide capture for storage in deep geologic formations. Elsevier; 2005. p. 787–813.
[18] Gaus I, Azaroual M, Czernichowski-Lauriol I. Reactive transport modelling of the impact of CO2 injection on the clayey cap rock at Sleipner
(North Sea). Chem Geol 2005; 217:319–337.
[19] Xu T, Apps JA, Pruess K. Mineral sequestration of carbon dioxide in a sandstone–shale system. Chem Geol 2005; 217:295–318.
[20] Gherardi F, Xu T, Pruess K. Numerical modeling of self-limiting and self-enhancing caprock alteration induced by CO2 storage in a depleted
gas reservoir. Chem Geol 2007; 244:103–129.
[21] Credoz A, Bildstein O, Jullien M, Raynal J, Pétronin J-C, Lillo M, Pozo C, Geniaut G. Experimental and modeling study of geochemical
reactivity between clayey caprocks and CO2 in geological storage conditions. Energy Procedia 2009; 1:3445–3452.
[22] Bildstein O, Kervévan C, Lagneau V, Delaplace P, Crédoz A, Audigane P, Perfetti E, Jacquemet N, Jullien M. Integrative modeling of
caprock integrity in the context of CO2 storage: evolution of transport and geochemical properties and impact on performance and safety
assessment. Oil Gas Sci Technol – Rev. IFP 2010; 65:485–502.
[23] Kohler E, Parra T, Vidal O. Clayey cap-rock behavior in H2O–CO2 media at low pressure and temperature conditions: An experimental
approach. Clay Clay Miner 2009; 57:616–637.
[24] Alemu BL, Aagaard P, Munz IA, Skurtveit E. Caprock interaction with CO2: A laboratory study of reactivity of shale with supercritical CO2
and brine. Appl Geochem 2011; 26:1975–1989.
14
Author name / Energy Procedia 00 (2017) 000–000
[25] Szabó Z, Hellevang H, Király C, Sendula E, Kónya P, Falus G, Török S, Szabó C. Experimental-modelling geochemical study of potential
CCS caprocks in brine and CO2-saturated brine. Int J Greenh Gas Con 2016; 44:262-275.
[26] Miller QRS, Wang X, Kaszuba JP, Mouzakis KM, Navarre-Sitchler AK, Alvarado V, McCray JE, Rother G, Banuelos JL, Heath JE.
Experimental study of porosity changes in shale caprocks exposed to carbon dioxide-saturated brine II: Insights from aqueous geochemistry.
Environ Eng Sci 2016; ahead of print. doi:10.1089/ees.2015.0592.
[27] Mouzakis KM, Navarre-Sitchler AK, Rother G, Banuelos JL, Wang X, Kaszuba JP, Heath JE, Miller QRS, Alvarado V, McCray JE.
Experimental study of porosity changes in shale caprocks exposed to carbon dioxide-saturated brine I: Evolution of mineralogy, pore
connectivity, pore size distribution, and surface area. Environ Eng Sci 2016; ahead of print. doi:10.1089/ees.2015.0588.
[28] Black JR, Haese RR. Batch reactor experimental results for GaMin’11: Reactivity of siderite/ankerite, labradorite, illite and chlorite under
CO2 saturated conditions. Energy Procedia 2014; 63:5443-5449.
[29] Van Olphen H, Fripiat JJ. Data handbook for clay minerals and other non-metallic minerals. Oxford: Pergamon Press; 1979.
[30] Chipera SJ, Bish DL. Baseline studies of the Clay Minerals Society source clays: Powder X-ray diffraction analyses. Clay Clay Miner 2001;
49:398–409.
[31] Madejová J, Komadel P. Baseline studies of the Clay Minerals Society source clays: Infrared methods. Clay Clay Miner 2001; 49:410–432.
[32] Mermut AR, Cano AF. Baseline studies of the Clay Minerals Society source clays: Chemical analyses of major elements. Clay Clay Miner
2001; 49:381-386.
[33] Kogel JE, Lewis SA. Baseline studies of the Clay Minerals Society source clays: Chemical analysis by inductively coupled plasma-mass
spectroscopy (ICP-MS). Clay Clay Miner 2001; 49:387-392.
[34] Mermut AR, Lagaly G. Baseline studies of the Clay Minerals Society source clays: Layer-charge determination and characteristics of those
minerals containing 2:1 layers. Clay Clay Miner 2001; 49:393-397.
[35] Köster MA. Mineralogical and chemical heterogeneity of three standard clay mineral samples. Clay Miner 1996; 31:417–422.
[36] Tóth J, Udvardi B, Kovács I, Falus G, Szabó C, Troskot-Čorbić T, Slavković R. Analytical development in FTIR analysis of clay minerals.
MOL Scientific Magazine 2012; 1:52–61.
[37] Grdadolnik J. ATR-FTIR spectroscopy: Its advantages and limitations. Acta Chim Slov 2002; 49:631–642.
[38] Madejová J. FTIR techniques in clay mineral studies. Vib Spectrosc 2003; 31:1-10.
[39] Kovács IJ, Udvardi B, Falus G, Földvári M, Fancsik T, Kónya P, Bodor E, Mihály J, Németh C, Czirják G, Ősi A, Vargáné Barna E, Bhattoa
HP, Szekanecz Z, Turza S. Practical - especially earth science - applications of ATR-FTIR spectrometry through some case studies. Bull
Hung Geol Soc 2015; 145:173-192.
[40] Fripiat JJ, Cruz ML, Bohor BF, Thomas Jr J. Interlamellar adsorption of carbon dioxide by smectites. Clay Clay Miner 1974; 22:23-30.
[41] Loring JS, Schaef HT, Turcu RVF, Thompson CJ, Miller QRS, Martin PF, Hu J, Hoyt DW, Qafoku O, Ilton ES, Felmy AR, Rosso KM. In
situ molecular spectroscopic evidence for CO2 intercalation into montmorillonite in supercritical carbon dioxide. Langmuir 2012;
28:7125−7128.
[42] Loring JS, Schaef HT, Thompson CJ, Turcu RVF, Miller QRS, Chen J, Hu J, Hoyt DW, Martin PF, Ilton ES, Felmy AR, Rosso KM. Clay
hydration/dehydration in dry to water-saturated supercritical CO2: Implications for caprock integrity. Energy Procedia 2013; 37:5443–5448.
[43] Galán E, Aparicio P. Experimental study on the role of clays as sealing materials in the geological storage of carbon dioxide. Appl Clay Sci
2014; 87:22–27.
[44] Jong SM, Spiers CJ, Busch A. Development of swelling strain in smectite clays through exposure to carbon dioxide. Int J Greenh Gas Con
2014; 24:149–161.
[45] Ferrage E, Lanson B, Michot LJ, Robert JL. Hydration properties and interlayer organization of water and ions in synthetic Na-smectite with
tetrahedral layer charge. Part 1. Results from X-ray diffraction profile modeling. J Phys Chem C 2010; 114:4515–4526.
[46] Bird P. Hydration–phase diagrams and friction of montmorillonite under laboratory and geologic conditions, with implications for shale
compaction, slope stability, and strength of fault gouge. Tectonophysics 1984; 107:235–260.
[47] Michels L, Fossum JO, Rozynek Z, Hemmen H, Rustenberg K, Sobas PA, Kalantzopoulos GN, Knudsen KD, Janek M, Plivelic TS, da Silva
GJ. Intercalation and retention of carbon dioxide in a smectite clay promoted by interlayer cations. Sci Rep 2015; 5:8775.
[48] Cooper CD, Mustard JF. Effects of very fine particle size on reflectance spectra of smectite and palagonitic soil. Icarus 1999; 142:557–570.
[49] Udvardi B, Kovács, IJ, Szabó C, Mihály J, Németh C. Aggregation of kaolinites and swelling-drying effect in microaggregates of bentonites.
Environmental Scientific Conference of the Carpathian Basin 2012; 140-145.
[50] Udvardi B, Kovács IJ, Fancsik T, Kónya P, Bátori M, Stercel F, Falus G, Szalai Z. Effects of particle size on the attenuated total reflection
spectrum of minerals. Appl Spectrosc 2016; doi:10.1177/0003702816670914