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| Titel |
Using oxygen isotopes to quantitatively assess residual CO2 saturation during the CO2CRC Otway Stage 2B Extension residual saturation test |
| VerfasserIn |
Sascha Serno, Gareth Johnson, Tara C. LaForce, Jonathan Ennis-King, Ralf Haese, Chris Boreham, Lincoln Paterson, Barry M. Freifeld, Paul J. Cook, Dirk Kirste, R. Stuart Haszeldine, Stuart M. V. Gilfillan |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122367
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| Publikation (Nr.) |
 EGU/EGU2016-1388.pdf |
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| Zusammenfassung |
| Recent research has shown that the oxygen isotope ratio (δ18O) of reservoir water can change
due to isotopic equilibrium exchange with injected CO2. These changes have been
successfully used to assess reservoir saturation with CO2. We present the first δ18O
measurements from a single-well experiment, the CO2CRC Otway 2B Extension
project, used to estimate levels of residual trapping of CO2. Following the initiation of
the drive to residual saturation in the reservoir, reservoir water δ18O decreased, as
predicted from the baseline isotope ratios of water and CO2, over a time span of
only a few days. The isotope shift in the near-wellbore reservoir water is the result
of isotope equilibrium exchange between residual CO2 and water. For the region
further away from the well, the isotopic shift in the reservoir water can also be
explained by isotopic exchange with mobile CO2 from ahead of the region driven to
residual, or continuous isotopic exchange between water and residual CO2 during its
back-production, complicating the interpretation of the change in reservoir water
δ18O in terms of residual saturation. A small isotopic distinction of the baseline
water and CO2 δ18O, together with issues encountered during the field experiment
procedure, further prevents the estimation of residual CO2 saturation levels from
oxygen isotope changes without significant uncertainty. The consistency of oxygen
isotope-based near-wellbore saturation levels and independent estimates based on
pulsed neutron logging indicates the potential of using oxygen isotope as an effective
inherent tracer for determining residual saturation on a field scale within a few days. |
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