Full Pore Size Characterization of Coal Pore Structure Based on CT Scanning

doi:10.3969/j.issn.1006-6535.2024.04.009

Abstract

Abstract: 12 samples of X coal from the Benxi Formation were collected in the DJ Block at the eastern edge of Ordos Basin,in order to explore the pore structure of deep and ultra-deep coal formations.The full pore size distribution characteristics of X coal were characterized by multi-experiment splicing method,based onthe three-dimensional reconstruction technology of digital core CT scanning and tests of high-pressure mercury intrusion,liquid nitrogen adsorption,and carbon dioxide adsorption.The study also compared and analyzed the distribution differences between the micropores,mesopores,and macropores in deep,medium,and shallow coal formations and their effects on adsorption and permeability.The results show that the reserving space of coal reservoirs is dominated by micropores and macropores,with fewer mesopores.In deep X coal formation,micropores and macropores on average account for 44.1% and 53.9%,respectively.While in shallow-to-medium X coal,micropores and macropores on average account for 34.8%,64.1%,respectively.The adsorption nanopores in deep coal are more developed.However,the development of micron-scale fractures in shallow-to-medium coal is better than that in deep coal.Through the analysis of the full pore size distribution characteristics,it is concluded that the proportion of macropore volume in shallow-to-medium X coal is higher,and the permeability is an order of magnitude higher than that of deep X coal,while the proportion of micropore volume in deep X coal is higher,indicating stronger adsorption capacity.Through quantitative characterization of the full aperture,the pore distribution characteristics of the reservoir at all levels are clarified,which provides data and theoretical support for the occurrence state and production mechanism of coalbed methane.

Key words: coal, full pore size splicing, micron-scale CT scanning, high-pressure mercury intrusion, liquid nitrogen adsorption, carbon dioxide adsorption, DJ Block at the eastern edge of Ordos Basin

CLC Number:

TD822

Zhu Wentao, Li Xiaogang, Ren Yong, Shi Binbin, Dai Ruirui, Hong Xing, Yang Xiao, Chen Guohui. Full Pore Size Characterization of Coal Pore Structure Based on CT Scanning[J]. Special Oil & Gas Reservoirs, 2024, 31(4): 71-80.

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