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| Titel |
Experimental evidence for effects of stress on the CO2 sorption capacity of coal under conditions relevant to ECBM |
| VerfasserIn |
Sander Hol, Colin J. Peach, Christopher J. Spiers |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034233
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| Zusammenfassung |
| Enhanced Coalbed Methane production (ECBM) involves the injection of CO2 to desorb
CH4 from coal seams, while trapping CO2 as a preferentially adsorbed phase. Successful
ECBM relies on a clear understanding of coal-CO2 interaction processes under the relevant
subsurface conditions. Though adsorption of CO2 by coal has been extensively studied in
experiments, few systematic studies have been done on the effects of stress state on CO2
sorption by coal. We have directly investigated the effects of stress on CO2 adsorption by coal
matrix material. To do this, we performed experiments in a one-dimensional oedometer-type
compaction cell, using granular (crushed and sieved) coal matrix material. The loose,
granular material was first equilibrated with CO2 at pressures of 10.0-20.0 MPa and
at a temperature of 40°C. The samples were then compacted at 40.0 MPa. After
unloading and re-equilibration with respect to CO2, the samples were re-loaded
in a stepwise manner to axial stresses up to 35.0 MPa. Changes in the volume of
CO2 present in the sample during this stepping procedure were measured using a
syringe pump. Our data show that stress reduces the adsorption capacity of the coal
matrix for CO2 by up to 20-50% under the conditions investigated. We explain our
observations in terms of an effect of the external applied effective stress upon the
free energy of adsorption in the nanoscale pores of the coal matrix. As reservoir
models currently do not consider the role of overburden and horizontal stresses on the
adsorption capacity in the coal seams, the effects of stress observed here may have
important implications for predictions of the in situ CO2 storage capacity of deep coal
formations.
Acknowledgements
The authors acknowledge Shell International for funding the research presented in this paper
(Contract No. 4600003671). Rick Wentinck, Niels van Wageningen and Claus Otto are
thanked for their support and valuable suggestions during the course of this study. Eimert
de Graaff, Gert Kastelein and Peter van Krieken are thanked for their technical
support. |
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