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| Titel |
Identification and determination of trapping parameters as key site parameters for CO2 storage for the active CO2 storage site in Ketzin (Germany) - Comparison of different experimental approaches and analysis of field data |
| VerfasserIn |
Kornelia Zemke, Axel Liebscher |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250111108
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| Publikation (Nr.) |
 EGU/EGU2015-11186.pdf |
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| Zusammenfassung |
| Petrophysical properties like porosity and permeability are key parameters for a safe
long-term storage of CO2 but also for the injection operation itself. The accurate
quantification of residual trapping is difficult, but very important for both storage
containment security and storage capacity; it is also an important parameter for dynamic
simulation.
The German CO2 pilot storage in Ketzin is a Triassic saline aquifer with initial conditions
of the target sandstone horizon of 33.5 Ë C/6.1 MPa at 630 m. One injection and two
observation wells were drilled in 2007 and nearly 200 m of core material was recovered for
site characterization. From June 2008 to September 2013, slightly more than 67 kt food-grade
CO2 has been injected and continuously monitored. A fourth observation well has
been drilled after 61 kt injected CO2 in summer 2012 at only 25 m distance to the
injection well and new core material was recovered that allow study CO2 induced
changes in petrophysical properties. The observed only minor differences between
pre-injection and post-injection petrophysical parameters of the heterogeneous formation
have no severe consequences on reservoir and cap rock integrity or on the injection
behavior.
Residual brine saturation for the Ketzin reservoir core material was estimated
by different methods. Brine-CO2 flooding experiments for two reservoir samples
resulted in 36% and 55% residual brine saturation (Kiessling, 2011). Centrifuge
capillary pressure measurements (pc = 0.22 MPa) yielded the smallest residual brine
saturation values with ~20% for the lower part of the reservoir sandstone and ~28% for
the upper part (Fleury, 2010). The method by Cerepi (2002), which calculates the
residual mercury saturation after pressure release on the imbibition path as trapped
porosity and the retracted mercury volume as free porosity, yielded unrealistic low
free porosity values of only a few percent, because over 80% of the penetrated
mercury remained in the samples after pressure release to atmospheric pressure. The
results from the centrifuge capillary pressure measurements were then used for
calibrating the cutoff time of NMR T2 relaxation (average value 8 ms) to differentiate
between the mobile and immobile water fraction (standard for clean sandstone 33
ms). Following Norden (2010) a cutoff time of 10 ms was applied to estimate the
residual saturation as Bound Fluid Volume for the Ketzin core materials and to
estimate NMR permeability after Timur-Coates. This adapted cutoff value is also
consistent with results from RST logging after injection. The maximum measured CO2
saturation corresponds to the effective porosity for the upper most CO2 filled sandstone
horizon. The directly measured values and the estimated residual brine saturations
from NMR measurements with the adapted cutoff time of 10 ms are within the
expected range compared to the literature data with a mean residual brine saturation of
53%.
A. Cerepi et al., 2002, Journal of Petroleum Science and Engineering 35.
M. Fleury et al., 2011, SCA2010-06.
D. Kiessling et al., 2010, International Journal of Greenhouse Gas Control 4.
B. Norden et al. 2010, SPE Reservoir Evaluation & Engineering 13.
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