Tectonic chemical properties of outburst coal
- Pennsylvania State Univ., University Park, PA (United States). Coal and Organic Petrology Labs.
- Peking Univ., Beijing (China). Dept. of Geology
- Jiaozuo Inst. of Tech., Henan (China). Dept. of Geology
Almost all outburst coal is known to have been tectonically deformed in fault and fold zones which underwent one or more episodes of strong structural deformation. The physical properties of outburst coal such as crushing strength and rate of gas desorption have been studied in the past. However, it can be difficult to reliably determine these physical coefficients from core sampling operations because the coal can be inadvertently pulverized during drilling. The development of a new index to predict the outburst potential of coal seams, and which is not influenced by sampling procedures, could be beneficial to mining safety technology. Tectonic stress may not only affect the original physical structure of outburst coal but also may bring about changes in its chemical properties. The most important aspect of these tectonically influenced chemical properties is that they not only predict the possibility of a coal outburst, but also are stable and independent of the physical changes imposed by drilling. Most of the chemical characteristics of coal display no obvious difference between normal undeformed coal (which is not subject to outbursts) and outburst coal. However, recent studies have shown that the chloroform extract yield is a very good index for differentiating these coals. Nineteen coal samples from five mines experiencing outbursts in the Pingdingshan coalfield, Henan, China, were analyzed. Their mean-maximum vitrinite reflectance in oil ranges from 0.97 to 1.28% and the mean random reflectance from 0.89 to 1.20%. The ash yield is between 3.18 and 7.47%. All samples were prepared to minus 180 m ({minus}80 mesh US); 30 g of each sample was extracted with chloroform in a Soxhlet apparatus for 72 h at 75 C. The mean extract yield of outburst coal is 1.45% (10 samples; range 0.58 to 2.11%) whereas that of the normal coal is 0.42% (9 samples; range 0.27 to 0.75%). The authors conclude that outburst coal has a higher chloroform extract yield than equivalent coal which has not been tectonically disturbed. The results presented here also suggest a reason why outburst coals tend to have higher gas contents than the same coals which are tectonically undeformed. The chloroform extract yield is an accepted measure of the hydrocarbon-generating potential of coals and other organic rocks. It appears that tectonic stress may modify the hydrocarbon generating potential of coals, generating more gas in comparison to equivalent normal coal. At the same time that the tectonic stress destroyed the physical integrity of outburst coal, it enhanced its gas content; the physical and chemical changes accompanied each other. These observations suggest that strongly deformed coalfields may be among the preferred areas to explore for coalbed methane resources.
- OSTI ID:
- 349244
- Report Number(s):
- CONF-980985-; ISBN 1-890977-15-2; TRN: IM9924%%245
- Resource Relation:
- Conference: 15. annual international Pittsburgh coal conference, Pittsburgh, PA (United States), 14-18 Sep 1998; Other Information: PBD: 1998; Related Information: Is Part Of Fifteenth annual international Pittsburgh coal conference: Proceedings; PB: [1500] p.
- Country of Publication:
- United States
- Language:
- English
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