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Effects of caprock sealing capacities on coalbed methane preservation: Experimental investigation and case study
- Source :
- Journal of Central South University. 26:925-937
- Publication Year :
- 2019
- Publisher :
- Springer Science and Business Media LLC, 2019.
-
Abstract
- Caprocks play an important role in the trapping of coalbed methane (CBM) reservoirs. To study the sealing capacities of caprocks, five samples with different lithologies of Neogene clayrock, Paleogene redbeds, Permian sandstone, Permian mudstone and Permian siltstone were collected and tested using experimental methods of microstructure observation, pore structure measurement and diffusion properties determination. Results indicate that with denser structures, lower porosities, much more developed micropores/transition pores and higher pore/throat ratios, mudstone and siltstone have the more ideal sealing capacities for CBM preservation when comparing to other kinds of caprocks; the methane diffusion coefficients of mudstone/siltstone are about 6 times higher than sandstone and almost 90 times higher than clayrock/redbeds. To further estimate the CBM escape through caprocks, a one-dimensional CBM diffusion model is derived. Modeling calculation result demonstrates that under the same thickness, the CBM sealing abilities of mudstone/siltstone are almost 100 times higher than those of clayrock/redbeds, and nearly 17 times higher than sandstone, which indicates that the coal seam below caprocks like clayrock, redbeds or sandstone may suffer stronger CBM diffusion effect than that below mudstone or siltstone. Such conclusion is verified by the case study from III3 District, Xutuan Colliery, where the coal seam capped by Paleogene redbeds has a much lower CBM content than that capped by the Permian strata like mudstone, siltstone and sandstone.
- Subjects :
- Red beds
Coalbed methane
Permian
Lithology
020209 energy
Metals and Alloys
General Engineering
02 engineering and technology
010502 geochemistry & geophysics
Neogene
01 natural sciences
Caprock
0202 electrical engineering, electronic engineering, information engineering
Petrology
Siltstone
Paleogene
Geology
0105 earth and related environmental sciences
Subjects
Details
- ISSN :
- 22275223 and 20952899
- Volume :
- 26
- Database :
- OpenAIRE
- Journal :
- Journal of Central South University
- Accession number :
- edsair.doi...........4e9f8aed884a04e7a6c736a0571ab081
- Full Text :
- https://doi.org/10.1007/s11771-019-4061-3