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| Titel |
Simulating CO2 injection into submarine, CH4-hydrate bearing sediments in high-pressure experiments |
| VerfasserIn |
Christian Deusner, Nikolaus Bigalke, Elke Kossel, Jean-Philippe Savy, Matthias Haeckel |
| 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 |
250051552
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| Zusammenfassung |
| Meeting the increasing demand for energy and simultaneously keeping cumulative CO2
emissions below a potentially dangerous threshold value is one of the most challenging tasks
of present times. The production of natural gas via injection of fossil-fuel derived CO2 into
submarine gas hydrate reservoirs could potentially be realized on industrial scales
in order to exploit these hydrocarbon energy sources in a CO2-neutral manner.
However, the mechanisms of hydrate dissociation and conversion under CO2-injection
conditions are not fully understood and various engineering aspects make a future
industrial application challenging. Within the German gas hydrate initiative SUGAR a
combination of high–pressure laboratory experiments and transport-reaction modelling is
used to elucidate the process mechanisms and technical parameters on different
scales.
The high-pressure systems presented here were developed and built to simulate conditions
in natural hydrate reservoirs (P , T ,Q, fluid composition, sedimentary settings) in both batch
and continuous operation and for different sample volumes (1mL to 2000mL). For carrying
out disturbance-free experiments, IR- and Raman-spectroscopy as well as NMR-imaging are
used for online monitoring and process visualization.
We used flow-through experiments with artificial sediment (CH4 hydrate and quartz sand)
to determine methane yields from CH4-hydrate decomposition using CO2-rich brines, pure
liquefied, supercritical as well as gaseous CO2. CH4 yields in flow-through experiments
were low when injecting either CO2-rich brines or CO2-seawater mixtures. Sample
permeability became severely impaired due to spontaneous formation of CO2-hydrate from
over-saturated solutions and large pressure spikes were followed by apparent sediment
fracturing. However, the injection of pure CO2 did not reduce permeability to that
extent because water availability was limited. Expectedly, CH4 yields were highest
with additional heat injection with supercritical CO2. To this end, high yields are
interpreted as a consequence of accelerated hydrate dissociation and subsequent
replacement of CH4 gas by supercritical and liquid CO2. The hypothetic two-step
mechanism of initial hydrate dissociation prior to reformation of CO2-hydrate was also
confirmed with Raman microscopy. It was shown that upon introduction of CO2 gas
the prevalent CH4-hydrate decomposes very quickly with respect to simultaneous
CO2-hydrate formation. Moreover, the spectroscopic analysis revealed that there
is no preferential release of methane from either of the two cages in the hydrate
structure.
Ongoing experiments focus on optimizing yields and efficiencies for CH4 recovery and
CO2 sequestration, especially trying to elucidate the effect of bulk sediment permeability on
the conversion dynamics. |
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