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| Titel |
Simulation of fluid-mineral kinetic reactions during CO2 storage using ChemApp and SUPCRT92 coupled to OpenGeoSys |
| VerfasserIn |
Dedong Li, Christof Beyer, Sebastian Bauer |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250052233
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| Zusammenfassung |
| After CO2 is injected into a deep underground saline formation, the initial geochemical
equilibrium state is changed, and a series of geochemical reactions between CO2, the pore
fluid and the minerals present is initiated. Most of these geochemical reactions are kinetically
controlled. For example, dissolution and precipitation of carbonates and silicates have to be
considered as kinetic reactions, as the reaction time scale exceeds the transport
timescale. The geochemical reactions and the flow and transport processes in the saline
formation thus interact in a complex way, influencing each other. The geochemical
kinetic reactions depend on the composition of the fluids present and the mineral
composition. For the required kinetic rate laws, adequate parameters are required. These
parameters fall into two groups, i.e. specific kinetic parameters which depend on the
individual kinetic rate law used, as well as thermodynamic parameters, such as reaction
equilibrium constants and activity coefficients of each species involved in the reaction
system. Equilibrium constants depend on temperature and pressure conditions,
activity coefficients of individual species depend on the system composition. During a
coupled reactive transport simulation, the change of these factors requires that these
thermodynamic parameters must be constantly updated. In order to calculate these necessary
parameters, we coupled two geochemical models, ChemApp and SUPCRT92, to the
multi-phase flow and transport simulator OpenGeoSys. Based on the Gibbs free
energy minimization method, ChemApp calculates activity coefficients of individual
species and equilibrium constants for each given geochemical kinetic reaction. The
SUPCRT92 program calculates thermochemical properties of all species involved
at various temperature and pressure conditions as well as solution compositions
using Helgeson-Kirkham-Flowers equations and databases. Based on the HKF
equations, the SUPCRT92 program has been widely applied in reactive transport
simulations.
This study reports the implementation and verification of the multi-component transport
code OpenGeoSys coupled with simulation of kinetic mineral reactions, where the basic
thermodynamic properties are obtained either by ChemApp or SUPCRT92. The coupled
simulator is verified by comparison against Phreeqc and other software. Benchmarks as well
as code verifications are presented. We then use our code to study reactive transport problems
in CO2 geological storage systems. Especially, the kinetics of dissolution and precipitation
reactions of carbonate and silicate minerals due to CO2 fluid migration can be simulated.
Using data from the Michigan Basin which is composed primarily of calcite and dolomite, we
study the kinetic reactions between fluid and cap rock and compare our simulation
results with experimental data to demonstrate the ability of our simulation program
for an assessment and prediction of CO2 geological storage. We compare the two
equilibrium geochemical methods and report the differences and their reasons. |
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