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| Titel |
Petrophysical laboratory invertigations of carbon dioxide storage in a subsurface saline aquifer in Ketzin/Germany within the scope of CO2SINK |
| VerfasserIn |
K. Zemke, J. Kummmerow, M. Wandrey, CO2SINK Group |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031298
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| Zusammenfassung |
| Since June of 2008 carbon dioxide has been injected into a saline aquifer at the Ketzin test
site [Würdemann et al., this volume]. The food grade CO2 is injected into a sandstone zone of
the Stuttgart formation at ca. 650 m depth at 35°C reservoir temperature and 62 bar reservoir
pressure.
With the injection of CO2 into the geological formation, chemical and physical reservoir
characteristics are changed depending on pressure, temperature, fluid chemistry and rock
composition. Fluid-rock interaction could comprise dissolution of non-resistant minerals in
CO2-bearing pore fluids, cementing of the pore space by precipitating substances from the
pore fluid, drying and disintegration of clay minerals and thus influence of the composition
and activities of the deep biosphere.
To testing the injection behaviour of CO2 in water saturated rock and to evaluate the
geophysical signature depending on the thermodynamic conditions, flow experiments with
water and CO2 have been performed on cores of the Stuttgart formation from different
locations including new wells of ketzin test site.
The studied core material is an unconsolidated fine-grained sandstone with porosity values
from 15 to 32 %.
Permeability, electrical resistivity, and sonic wave velocities and their changes with pressure,
saturation and time have been studied under simulated in situ conditions. The flow
experiments conducted over several weeks with brine and CO2 showed no significant changes
of resistivity and velocity and a slightly decreasing permeability. Pore fluid analysis showed
mobilization of clay and some other components.
A main objective of the CO2Sink laboratory program is the assessment of the effect of
long-term CO2 exposure on reservoir rocks to predict the long-term behaviour of
geological CO2 storage. For this CO2 exposure experiments reservoir rock samples
were exposed to CO2 saturated reservoir fluid in corrosion-resistant high pressure
vessels under in situ temperature and pressure conditions over a period of several
months.
Before and after the CO2 exposure experiment cyclic measurements of physical properties
were carried out on these cores in a mechanical testing system. After experimental runs of up
to 3 months no significant changes in flow and petrophysical data were observed. [For the
microbilogical studies see Wandrey et al., this volume.]
To study the impact of fluid-rock interactions on petrophysical parameters, porosity and pore
radii distribution have been investigated before and after the experiment by NMR
relaxation and mercury-injection. NMR measurements on rock core plugs saturated with
brine may return valuable information on the porous structure of the rock core. The
distribution of NMR-T2 values (CPMG) reflects the pore sizes within the rock
core. NMR pore size is a derivative of the ratio pore surface/volume. The mercury
injection pore size is an area-equivalent diameter of the throats connecting the pore
system.
Most of the tested samples show in the NMR measurements a slightly increasing
porosity and a higher part of large pores. The mercury measurements and thin- section
for microstructural characterisation after the CO2 exposure will be done at a later
date. |
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