Summary
This paper aims to investigate the effect of temperature and effective
stress on coal permeability. Through the experiment, we find a reversal
phenomenon in which the coal permeability presents different change trends as
temperature increases at two sides of the reverse point.
The term "critical effective stress" refers to the effective stress at the
reverse point. When effective stress is lower than the critical effective
stress, the outward expansion effect of the coal block caused by grain and gas
swell is greater than compaction effect as temperature increases under low
effective stress condition. Therefore, the coal expands primarily outward,
which results in fissure opening and permeability increase. When effective
stress is higher than the critical effective stress, high effective stress
limits the coal?s outward expansion. The coal expands inward with increasing
temperature, thus causing fissure closure and permeability decrease.
On the basis of dimension analysis and regression analysis, combined with
experimental data, this paper develops a high-precision semitheoretical coal
permeability model of Qinshui basin in China. Simultaneously, what this paper
presents is a permeability prediction method: measuring coal core permeability
and performing dimension analysis and regression analysis. With this work done,
we can establish a similar permeability model suitable for other target zones.
Thus, the analytical method presented in this paper provides a basis for coal
permeability prediction.
© 2013. Society of Petroleum Engineers
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History
- Original manuscript received:
20 July 2011
- Revised manuscript received:
9 May 2012
- Manuscript approved:
16 May 2012
- Published online:
22 January 2013
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