Variation of Petrophysical Properties and Adsorption Capacity in Different Rank Coals: An Experimental Study of Coals from the Junggar, Ordos and Qinshui Basins in China

Yingjin Wang, Dameng Liu, Yidong Cai and Xiawei Li
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Yingjin Wang: School of Energy Resources, China University of Geosciences, Beijing 100083, China
Dameng Liu: School of Energy Resources, China University of Geosciences, Beijing 100083, China
Yidong Cai: School of Energy Resources, China University of Geosciences, Beijing 100083, China
Xiawei Li: School of Energy Resources, China University of Geosciences, Beijing 100083, China

Energies, 2019, vol. 12, issue 6, 1-19

Abstract: The petrophysical properties of coal will vary during coalification, and thus affect the methane adsorption capacity. In order to clarify the variation rule and its controlling effect on methane adsorption, various petrophysical tests including proximate analysis, moisture measurement, methane isothermal adsorption, mercury injection, etc. were carried out on 60 coal samples collected from the Junggar, Ordos and Qinshui basins in China. In this work, the boundary values of maximum vitrinite reflectance (R o,m ) for dividing low rank, medium rank and high rank coals are set as 0.65% and 2.0%. The results show that vitrinite is the most abundant maceral, but the maceral contents are controlled by sedimentation without any relation to coal rank. Both the moisture content and porosity results show higher values in the low ranks and stabilized with R o,m beyond 1%. R o,m and V L ( daf ) show quadratic correlation with the peak located in R o,m = 4.5–5%, with the coefficient (R 2 ) reaching 0.86. P L decrease rapidly before R o,m = 1.5%, then increase slowly. DAP is established to quantify the inhibitory effect of moisture on methane adsorption capacity, which shows periodic relationship with R o,m : the inhibitory effect in lignite is the weakest and increases during coalification, then remains constant at R o,m = 1.8% to 3.5%, and finally increases again. In the high metamorphic stage, clay minerals are more moisture-absorbent than coal, and the inherent moisture negatively correlates with the ratio of vitrinite to inertinite ( V / I ). During coalification, micro gas pores gradually become dominant, fractures tends to be well oriented and extended, and clay filling becomes more common. These findings can help us better understand the variation of petrophysical properties and adsorption capacity in different rank coals.

Keywords: coal rank; petrophysical properties; coalbed methane; adsorption capacity (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View complete reference list from CitEc
Citations: View citations in EconPapers (5)

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