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| Titel |
Development of Kinetic Interface Sensitive Tracers (KIS-Tracer) for Supercritical Carbon Dioxide Injections into Deep Saline Aquifers |
| VerfasserIn |
M. Schaffer, F. Maier, T. Licha, M. Sauter |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250060072
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| Zusammenfassung |
| The storage of captured CO2 into geological formations is recently one of the most
promising technologies to mitigate anthropogenic greenhouse gas emissions into
the earth’s atmosphere. Deep saline aquifers are considered as the most potential
sequestration sites of CO2 due to their huge storage capacities of several thousand
Gt.
Ongoing research deals mainly with the investigation of relevant physico-chemical
processes, the fate of CO2 and the risk assessment during and after supercritical CO2
(scCO2) injections. The occurring processes at the interface between injected scCO2 and
formation brine play a major role to evaluate the fate and behavior of scCO2 in the reservoir.
This is because the interface represents a reactive zone where numerous physico-chemical
processes like dissolution of scCO2 in water as well as dissolution and precipitation of
minerals take place. In most cases it is desired to maximize the interface size to
increase the storage efficiency. Therefore, knowledge on interface size and dynamics
would allow the observation of plume spreading and the detection of mixing or
fingering effects. In order to gain this information innovative tracers are necessary
which are able to quantify the temporal and spatial development of scCO2/water
interfaces. As a result, it may be possible to assess the storage efficiency and to
optimize subsequent injections. Up to now, such time-dependent tracers for reservoir
studies are not available and limited to equilibrium tracers (known as partitioning and
interfacial tracers, respectively). Therefore, novel reactive tracers (KIS-Tracers)
are developed to overcome this gap. The idea is to find suitable molecules which
allow the implementation of a defined chemical reaction at the interface. Due to
the known kinetic constants the change of interface size can be characterized over
time.
The new tracer is injected together with the supercritical CO2 (scCO2) into a deep saline
aquifer. Afterwards, the tracer adsorbs at the interface and undergoes hydrolysis in contact
with water. As a consequence, two water soluble reaction products are formed and can be
measured in the water phase over time. Here, the reaction kinetics is the rate-limiting
step for the phase transfer and strongly dependents on reservoir properties, such as
temperature and pH. Such tracer molecules must have the following properties: i)
low polarity (high log KOW) to ensure high scCO2 solubility and to minimize
distribution into the water phase; (ii) at least one highly water soluble reaction
product, which does not do partitioning back into the scCO2 phase; (iii) low detection
limit.
On the basis of naphthalenesulfonic acid, an established geothermal tracer, different
molecules with the desired properties were synthesized and tested in the laboratory. For
studying the occurring processes at the interface under atmospheric pressure conditions the
scCO2 was replaced with a non-polar organic solvent. The experiments were conducted in a
static batch system with constant interfacial area as well as in a dynamic system with
changing interface size. In parallel, a macroscopic model which couples mass transfer and
reaction kinetics is developed to interpret the data. In conclusion, experiments indicate that
the integration of hydrolysis kinetics is possible and even one of the reaction products may be
used as additional partitioning tracer, i.e. for measuring the residual saturation. |
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