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| Titel |
Displacement and Mass Transfer Between Saturated and Unsaturated CO2-Brine Systems in Sandstone |
| VerfasserIn |
Holger Ott, Steffen Berg, Sjam Oedai |
| 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 |
250049044
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| Zusammenfassung |
| The process of displacement and mass transfer between CO2 and brine, which are
relevant for the prediction of plume migration and pore-space utilization during CO2
injection in saline aquifers, were studied by conducting unsteady-state core flood
experiments in nearly homogeneous Berea sandstone rock. Mutually saturated and
unsaturated CO2 and brine phases were injected in the rock under realistic sequestration
conditions.
Relative permeability and capillary pressure curves were extracted by history matching
the unsteady state experiments conducted with mutually saturated CO2 and brine. As a
reference and for comparison, decane–brine primary drainage was conducted on
the same sample. The CO2–brine relative permeability was found to be different
from the decane–brine relative permeability (which had been validated against
steady-state experiments on twin-samples), reflecting the change in the wetting
state from water-wet decane–brine/Berea to the rather intermediate-wet behavior of
CO2–brine/Berea, which is in agreement with literature data on contact-angles for the two
cases. However, the CO2 brine data are somewhat different from data on the same rock type
as reported by Perrin and Benson (2010) which is likely a consequence of sample
heterogeneity.
Aspects of the mass transfer between the CO2 and the brine phase were studied by
drainage and imbibition with unsaturated phases. When comparing saturated and unsaturated
CO2–brine primary drainage, the mass transfer due to mutual solubility leads to two
effects: (1) evaporation in a 2-3 cm wide zone at the inlet due to water dissolving in
CO2 and (2) a diminished displacement of brine by CO2 due to CO2 dissolving
in brine. In addition, an imbibition experiment was conducted where unsaturated
brine was injected into rock filled with mutually saturated CO2 and brine phase at
near-residual CO2 saturation. After the CO2–saturated brine had been miscibly
displaced by unsaturated brine, dissolution of the trapped CO2 in the injected brine was
subsequently observed. These experiments represent the transition from residual
trapping to solubility trapping and indicate the time and length scales involved. |
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