Small angle X-ray scattering mapping and kinetics study of sub-critical CO₂ sorption by two Australian coals

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• 作者：Andrzej P. Radliń ; ski ; Tara L. Busbridge ; Evan Mac A. Gray ; Tomasz P. Blach ; David J. Cookson
• 关键词：Adsorption kinetics ; Diffusion half-time ; Small-angle X-ray scattering ; Carbon dioxide ; Geological storage ; Coal
• 刊名：International Journal of Coal Geology
• 出版年：2009
• 出版时间：7 January 2009
• 年：2009
• 卷：77
• 期：1-2
• 页码：80-89
• 全文大小：1549 K

文摘

Time- and position-resolved synchrotron small angle X-ray scattering data were acquired from samples of two Australian coal seams: Bulli seam (Bulli 4, R_o = 1.42 % , Sydney Basin), which naturally contains CO₂ and Baralaba seam (R_o = 0.67 % , Bowen Basin), a potential candidate for sequestering CO₂. This experimental approach has provided unique, pore-size-specific insights into the kinetics of CO₂ sorption in the micro- and small mesopores (diameter 5 to 175 Å) and the density of the sorbed CO₂ at reservoir-like conditions of temperature and hydrostatic pressure.

For both samples, at pressures above 5 bar, the density of CO₂ confined in pores was found to be uniform, with no densification in near-wall regions. In the Bulli 4 sample, CO₂ first flooded the slit pores between polyaromatic sheets. In the pore-size range analysed, the confined CO₂ density was close to that of the free CO₂. The kinetics data are too noisy for reliable quantitative analysis, but qualitatively indicate faster kinetics in mineral-matter-rich regions.

In the Baralaba sample, CO₂ preferentially invaded the smallest micropores and the confined CO₂ density was up to five times that of the free CO₂. Faster CO₂ sorption kinetics was found to be correlated with higher mineral matter content but, the mineral-matter-rich regions had lower-density CO₂ confined in their pores. Remarkably, the kinetics was pore-size dependent, being faster for smaller pores.

These results suggest that injection into the permeable section of an interbedded coal-clastic sequence could provide a viable combination of reasonable injectivity and high sorption capacity.