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MODELING OF THE LABORATORY TESTS OF INTERACTION OF THE NaNO3-NaOH FLUIDS WITH SANDSTONE ROCKS FROM DEEP RADIONUCLIDE REPOSITORY SITE, USING TOUGHREACT
A.V. Kiryukhin 1, E.P. Kaymin2, E.V. Zakharova2, А.А. Zubkov3
1Institute of Volcanology and Seismology FEB RAS, Piip-9, Petropavlovsk-Kamchatsky, Russia, 683006
2- Institute of Physical Chemistry and Electrochemistry RAS, Leninsky-31, Moscow, Russia, 119991
3- Siberia Chemical Plant, Kurchatova-1, Seversk, Russia
ABSTRACT
TOUGHREACT modeling was used to reproduce laboratory tests with sandstone
samples collected from deep radionuclide repository site in Siberia Chemical Plant.
Laboratory test includes injection of alkaline fluids into sandstone samples at 70оС.
Modeling results were compared with observed test data (mineral phase change,
transient concentration data at the outlet of sample column). Some minerals were
restrain in the model to precipitate or dissolve according to laboratory test results.
Model and test convergence in mineral phases (Na-smectite and kaolinite
precipitation in the model, quartz, microcline, chlorite and biotite dissolution in the
model) were obtained. Nevertheless it was not found possible to generate sodium
carbonates in the model (while sodium clearly observed in the test). Transient
chemical concentration data at the outlet of sample column match Na only. It’s
concluded that the model should be improved in the future work to better match
observed data.
Chemical Input Data
Initial mineral fractions are shown in Table 1, parameters of kinetic water-rock
chemical interaction assigned the same as in (Kiryukhin et al, 2004) paper (E aenergy of activation, kJ/kmole), while other parameters were corrected during model
calibration (Table 2). Chemical compositions of the initial solution (natural pore fluids)
and injected fluid are shown in Tables 3 and 4, correspondingly.
MODEL CALIBRATION
Calibration Data
Two tests with duration of 79 days and 42 days correspondingly were performed
with injection mass flux at average level 2.50 10-5 kg/s m2. During test (at times 9,
16, 23, 30, 32, 58, 79 days) sampling of fluid took place at column outlet for
chemical analysis (Na, Al, Si, Ca, Mg, K, Sr). Microprobe analysis of mineral
composition of samples after testing was done. Microprobe analysis performed
based on Link INCA ENERGY200 to electronic scan facility CamScan MV-2300.
A.A. Grafchikov (Institute of Experimental Mineralogy RAS) took participation in this
analysis.
c
d
a
INTRODUCTION
TOUGHREACT is a computer code capable to simulate thermal-hydrodynamicchemical (THC) processes including multiphase nonisothermal transport and
kinetics of the rock - fluid chemical interaction. The THC processes and secondary
minerals associations observed in some drilled geothermal fields of the recent
volcanic activity areas have been successfully reproduced by TOUGHREACT
simulations (Xu, T. and Pruess, K., 2001, A.V. Kiryukhin et al, 2004). Similar
processes took place during waste radionuclide fluids injection in sandstones
aquifers. When liquid radionuclide waste injected in layer type reservoirs (Siberia
Chemical Plant (SCP), (Seversk), Mining-Chemical Plant (MCP) (Zheleznogorsk) –
chemical interaction with natural pore fluids and clay minerals of the deep
repository site took place. New secondary minerals created, while primary minerals
dissolve, temperature increase due to radiogenic heat release (A.I. Rybalchenko et
al, 1994). Monitoring of the hydrogeological parameters in the wells, as well as
laboratory experiments at P-T conditions corresponding to physical and chemical
processes in repository sites conducted to get reliable information on processes
there (А.А. Zubkov et al, 2002, E.P. Kaymin et al, 2004). Reliable numerical model
needed to forecast process of migration of radionuclides and to guaranty safety
condition in repository sites too. In this study, TOUGHREACT was used to
reproduce laboratory experiment of the process of technogenic alteration observed
in sandstones (obtained from deep repository site) as a result of chemical
interaction during NaNO3-NaOH fluid injection in rock samples at temperature
70оС. Modeling results calibrated against observed secondary minerals, generated
during laboratory experiment and identified based on microprobe analysis, and
against transient chemistry data of fluids, discharged from the core outlet during
laboratory experiment.
MODEL SETUP
In this study, TOUGHREACT was used to reproduce laboratory experiment of the
process of technogenic alteration observed in sandstones. In the model ,
adjective and diffusive transport of aqueous chemical species is considered.
Mineral dissolution/precipitation can proceed at equilibrium and /or under kinetic
conditions, according to the following rate law:
r = kS (1-Q/K) exp(Ea/(R*298.15)-Ea/(RT)),
where k – kinetic constant of the chemical dissolution/precipitation at 250C,
mole/s·m2; S – specific reactive surface area, m 2/m3; Q – is activity product; K – is
equilibrium constant for mineral-water interaction; Ea – is the activation energy,
kJ/kmole; R – is the gas constant, kJ/kmole K, and T – is temperature, K.
Temperature effects are also considered for geochemical reaction calculations in
which equilibrium and kinetic data are functions of temperature.
CONCLUSIONS
b
e
f
g
h
Scan electron images of samples (E.P. Kaymin data): a- Chlorite (Chl) replacement by montmorillonite (Mont), b- Muscovite (Ms) replacement by kaolinite (Kaol), c- Biotite (Bt) replacement by
montmorillonite (Mont), d- K-feldspar (Kfs) replacement by montmorillonite (Mont) , e- grains of
magnetite hosted in clay minerals,f- magnetite (white) inside of montmorillonite (grey) replaced
biotite grain, g- sodium or trona (Na) release in form of crust and regions in montmorillonite
(Mont),h- sodium or trona (Na) release in form of regions in montmorillonite (Mont).
Note: black space is polymeric matrix.
Flow and Solution Input Data
According to the Laboratory test data 700С isothermal conditions with mass flux 2.50
10-5 kg/s m2 and pressure 3.0MPa were assigned in the model. Sample porosity
assigned 0.2. The length of the model correspond to the length of test sample 15 cm.
1-D numerical grid generated includes 32 elements: B 1 – source of injected fluid
(element volume 5.00E+20 m3, R 1- R 30 elements represents sandstone column of
15 cm length, each element with width of 0.005 m, and D 1 – inactive element with
specified pressure 3.0 MPa, which correspond to discharge from the column outlet.
Figure above: Modeling results of mineral fraction change along
injection steamline in the sandstone column.
Figure left: Modeling (lines) and laboratory test (solid circles)
match (transient chemical concentrations of fluids).
Modeling Results
TOUGHREACT modeling of the laboratory test (run #7) yield the following results:
(1) Mineral phase fractions change. By the end of 79 day alkaline solution injection:
quartz - dissolve (from 9.2 10-5 to 9.8 10-5), microcline dissolve (from 3.1 10-6 to 3.2
10-6), albite-low - dissolve (to 1.4 10-6), Na-smectite (montmorillonite) precipitate in
the middle and outlet part of column (up to 1.8 10-3), kaolinite – precipitate in the
middle and outlet part of column (up to 1.1 10-5), chlorite – dissolve (3.0 10-9),
muscovite – dissolve everywhere (from 6.3 10-5 to 7.3 10-5). Secondary mineral
phases (Na-smectite and kaolinite) were formed during first 9 days only. No sodium
carbonate precipitations was obtained in the model (while abundant sodium
carbonates observed during laboratory test).
(2) Match of observed and modeling transient chemical concentrations of fluid
sampled from sandstone column outlet (run #7)shows the following. pH match show
the same trend of model and experiment, while absolute modeling values 2.6 units
greater. Na concentrations from model match those from the experiment. К match
show model 3 times less values than experiment. Ca match model and experiment
show the same trend, while absolute values in the model 2-3 orders less than
experiment. Mg match show the same trend in model and experiment, while, model
absolute values are 1-2 orders less. Al match show model yield 4 order greater
compare experiment. Si match show convergence in the first times, while later model
concentrations 3 times greater experiment. It was also found that change of rate
constants of mineral precipitations (kS) for Na-smectite and kaolinite (Table 3) has
no effect on рН and outlet discharge transient chemical concentrations.
(1) TOUGHREACT modeling was used to reproduce laboratory tests with
sandstones samples collected from deep radionuclide repository site in Siberia
Chemical Plant. Laboratory test include injection of alkaline fluids into sandstones
samples at 70оС.
(2) Model and test convergence in mineral phases (Na-smectite and kaolinite
precipitation in the model, quartz, microcline, chlorite and biotite dissolution in the
model) were obtained due to restrain for some minerals to precipitate /dissolve.
Nevertheless it was not found possible to generate sodium carbonate in the model
(while sodium clearly observed in the test). Transient chemical concentrations data
at the outlet of sample column match Na only. pH match show the same trend of
model and experiment, while absolute modeling values 2.6 units greater. Ca and Mg
match model and experiment show the same trend, while absolute values in the
model 2-3 orders less than experiment.
(3) The main reason model and laboratory test mis-match seems to be
TOUGHREACT not taking into account mineral/mineral chemical reactions. In
laboratory test was found K release to solutions, and Al consumed by secondary
minerals due to biotite, K-feldspars, muscovite replacing by clay minerals,
глинистыми минералами. If such reactions will be implemented in TOUGHREACT,
then convergence of modeling and laboratory test data may improve.
ACKNOWLEDGEMENTS
We express our gratitude to T. Xu, N.Spycher (Lawrence Berkeley National
Laboratory) for valuable comments and suggestions, B.N. Ryzhenko and О.А.
Limantseva (GeoChi RAS), I.B. Slovtsov (IVS FEB RAS) for additional
thermodynamic calculations. This work was supported by Siberia Chemical Plant,
FEB RAS project 06-I-ОНЗ-109 and RFBR project 06-05-64688-а.
REFERENCES:
А.А. Zubkov, О.V. Makarova, V.V. Danilov, Е.V.
Zakharova, Е.P. Kaymin, К.А. Menyailo, А.I. Rybalchenko,
Technogenic geochemical processes during injection of
the liquid radionuclide waste into sandstones layer type
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A.V. Kiryukhin, М.Y. Puzankov, I.B. Slovtsov et al,
Thermal-Hydrodynamic-Chemical modeling
processes of secondary mineral precipitation in
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“Vulcanologia and Seismologia”, 32 p.).
Rybalchenko A.I., Pimenov M.K., Kostin P.P. et al.
Е.P. Kaymin, Е.V. Zakharova, L.I. Konstantinova, А.А.
Deep injection of liquid radionuclide waste.
Graphchikov, L.Y. Аranovich, V.М. Shmonov, Study of the Мoscow, IzdAT publ., 1994, 256 p. (in Russian).
interaction of alkaline radionuclide waste with sanstone
rocks, Geoecology, Engineering Geology, Hydrogeology, Xu, T. and Pruess, K., 2001a, On Fluid Flow and
Geocriology, 2004, №5, p.427-432.
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