Constant volume CBM reservoirs: An important principle

Massarotto, Paul, Golding, Suzanne D. and Rudolph, Victor (2009). Constant volume CBM reservoirs: An important principle. In: 2009 International Coalbed and Shale Gas Symposium technical session papers. 2009 International Coalbed and Shale Gas Symposium/RPSEA Forum, Tuscaloosa, Alabama, United States, (). 18-21 May 2009.

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Author Massarotto, Paul
Golding, Suzanne D.
Rudolph, Victor
Title of paper Constant volume CBM reservoirs: An important principle
Conference name 2009 International Coalbed and Shale Gas Symposium/RPSEA Forum
Conference location Tuscaloosa, Alabama, United States
Conference dates 18-21 May 2009
Proceedings title 2009 International Coalbed and Shale Gas Symposium technical session papers
Place of Publication Tuscaloosa, Alabama, United States
Publisher University of Alabama
Publication Year 2009
Sub-type Fully published paper
Total pages 19
Language eng
Abstract/Summary Much research and many field trials have shown that the permeability of coal seams varies inversely with the effective stress acting on coal. It was later theorized by Gray (1992) that desorption-induced matrix shrinkage may counter-act the effect of external stresses, allowing permeability to increase, depending on the relative strength of the two phenomenon. This paper explores the geomechanical theory of reservoir stiffness and the arch-bridging effect, and uses operating coal mine evidence, to support the development of the important principle of a “constant volume” boundary condition applying to most deep CBM reservoirs, as opposed to a constant external stress condition. This principle allows for an initial external stress state to exist in a coal seam, and shows how the acting stress state is dynamic and generally trends lower with matrix shrinkage, allowing permeability to increase as depletion of the CBM reservoir proceeds. Laboratory data on measured permeability under both constant external stress conditions and constant volume conditions shows the importance of this principle; permeability increases of between 100% and 1200% can be experienced, depending on the stage of depletion and thus desorption. Field performance from producing CBM reservoirs will be referenced to confirm the reality and significance of permeability enhancement due to matrix shrinkage in the context of constant volume behaving deep CBM reservoirs.
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status UQ
Additional Notes Paper # 0926

 
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Created: Wed, 11 Jan 2012, 15:57:11 EST by Professor Victor Rudolph on behalf of School of Chemical Engineering