Strain development in unconfined coals exposed to CO2, CH4 and Ar

effect of moisture

Frank van Bergen, Chris Spiers, Geerke Floor, Pieter Bots

Research output: Contribution to journalArticle

82 Citations (Scopus)

Abstract

Field experiments and laboratory studies have shown that swelling of coal takes place upon contact with carbon dioxide at underground pressure and temperature conditions. Understanding this swelling behavior is crucial for predicting the performance of future carbon dioxide sequestration operations in unminable coal seams conducted in association with methane production. Swelling is believed to be related to adsorption on the internal coal surface. Whereas it is well established that moisture influences the sorption capacity of coal, the influence of water on coal swelling is less well-defined. This paper presents the results of laboratory experiments to investigate the effect of moisture on coal swelling in the presence of carbon dioxide, methane and argon. Strain development of an unconfined sample of about 1.0-1.5 mm3 at 40 °C and 8 MPa (and at other pressures) was observed in an optical cell under a microscope as a function of time. Both air dried and moisturized samples were used. Results confirmed different swelling behaviors of coal with different substances: carbon dioxide leads to higher strain than methane, while exposure to argon leads to very little swelling. The experiments on moisturized samples seem to confirm the role of moisture as a competitor to gas molecules for adsorption sites. Adsorption of water could also explain the observed swelling due to water uptake at atmospheric pressure. A re-introduction of carbon dioxide, after intermediate gas release, results in higher strains which indicate a drying effect of the carbon dioxide on the coal. The results of this study show that the role of water cannot be ignored if one wants to understand the fundamental processes that are taking place in enhanced coalbed methane operations. © 2008 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)43-53
Number of pages11
JournalInternational Journal of Coal Geology
Volume77
Issue number1-2
DOIs
Publication statusPublished - 2009

Fingerprint

swelling
Swelling
Moisture
moisture
Coal
coal
Carbon dioxide
carbon dioxide
Methane
methane
argon
adsorption
Adsorption
Argon
Water
coalbed methane
effect
Experiments
water uptake
reintroduction

Keywords

  • argon
  • carbon dioxide
  • methane
  • moisture
  • swelling

Cite this

van Bergen, Frank ; Spiers, Chris ; Floor, Geerke ; Bots, Pieter. / Strain development in unconfined coals exposed to CO2, CH4 and Ar : effect of moisture. In: International Journal of Coal Geology. 2009 ; Vol. 77, No. 1-2. pp. 43-53.
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abstract = "Field experiments and laboratory studies have shown that swelling of coal takes place upon contact with carbon dioxide at underground pressure and temperature conditions. Understanding this swelling behavior is crucial for predicting the performance of future carbon dioxide sequestration operations in unminable coal seams conducted in association with methane production. Swelling is believed to be related to adsorption on the internal coal surface. Whereas it is well established that moisture influences the sorption capacity of coal, the influence of water on coal swelling is less well-defined. This paper presents the results of laboratory experiments to investigate the effect of moisture on coal swelling in the presence of carbon dioxide, methane and argon. Strain development of an unconfined sample of about 1.0-1.5 mm3 at 40 °C and 8 MPa (and at other pressures) was observed in an optical cell under a microscope as a function of time. Both air dried and moisturized samples were used. Results confirmed different swelling behaviors of coal with different substances: carbon dioxide leads to higher strain than methane, while exposure to argon leads to very little swelling. The experiments on moisturized samples seem to confirm the role of moisture as a competitor to gas molecules for adsorption sites. Adsorption of water could also explain the observed swelling due to water uptake at atmospheric pressure. A re-introduction of carbon dioxide, after intermediate gas release, results in higher strains which indicate a drying effect of the carbon dioxide on the coal. The results of this study show that the role of water cannot be ignored if one wants to understand the fundamental processes that are taking place in enhanced coalbed methane operations. {\circledC} 2008 Elsevier B.V. All rights reserved.",
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Strain development in unconfined coals exposed to CO2, CH4 and Ar : effect of moisture. / van Bergen, Frank; Spiers, Chris; Floor, Geerke; Bots, Pieter.

In: International Journal of Coal Geology, Vol. 77, No. 1-2, 2009, p. 43-53.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Strain development in unconfined coals exposed to CO2, CH4 and Ar

T2 - effect of moisture

AU - van Bergen, Frank

AU - Spiers, Chris

AU - Floor, Geerke

AU - Bots, Pieter

PY - 2009

Y1 - 2009

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AB - Field experiments and laboratory studies have shown that swelling of coal takes place upon contact with carbon dioxide at underground pressure and temperature conditions. Understanding this swelling behavior is crucial for predicting the performance of future carbon dioxide sequestration operations in unminable coal seams conducted in association with methane production. Swelling is believed to be related to adsorption on the internal coal surface. Whereas it is well established that moisture influences the sorption capacity of coal, the influence of water on coal swelling is less well-defined. This paper presents the results of laboratory experiments to investigate the effect of moisture on coal swelling in the presence of carbon dioxide, methane and argon. Strain development of an unconfined sample of about 1.0-1.5 mm3 at 40 °C and 8 MPa (and at other pressures) was observed in an optical cell under a microscope as a function of time. Both air dried and moisturized samples were used. Results confirmed different swelling behaviors of coal with different substances: carbon dioxide leads to higher strain than methane, while exposure to argon leads to very little swelling. The experiments on moisturized samples seem to confirm the role of moisture as a competitor to gas molecules for adsorption sites. Adsorption of water could also explain the observed swelling due to water uptake at atmospheric pressure. A re-introduction of carbon dioxide, after intermediate gas release, results in higher strains which indicate a drying effect of the carbon dioxide on the coal. The results of this study show that the role of water cannot be ignored if one wants to understand the fundamental processes that are taking place in enhanced coalbed methane operations. © 2008 Elsevier B.V. All rights reserved.

KW - argon

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KW - methane

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