AUTHOR=Wang Qian , Su Xianbo , Jin Yi , Chen Peihong , Zhao Weizhong , Yu Shiyao 

TITLE=Pore structure characterization for coal measure shales of the Xiashihezi Formation in the Sunan Syncline block, southern North China basin

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.1017429

DOI=10.3389/feart.2022.1017429

ISSN=2296-6463

ABSTRACT= To characterize the coal measure shale pore structure of the Xiashihezi Formation in Sunan Syncline block, a series of experiments were conducted. Results show that the main components of the shales are clay minerals and quartz, and organic matter, fluid escaping, interlayer, intercrystalline as well as interparticle pores are well developed. The shale pore specific surface area (SSA) is concentrated in the pores with the size of <50 nm, and is significantly higher in the pores with the size of <5 nm, indicating these pores have important effect on gas adsorption. The shale pore volume is mainly concentrated near the pore size of 10 nm, followed by 10,000-100,000 nm, indicating that besides the fractures, the matrix pores with a size of about 10 nm contribute the most to the pore volume and the free gas accumulation. The volume and SSA of the micropore, small pore and mesopore increase with the TOC content when it is lower than 6%, leading to higher porosity and total pore SSA of the shales. However, this positive correlation disappears under the compaction effect when the TOC content is higher than 6%. The clay mineral content has negative correlation with the volume and SSA of the mesopore and macropore under the compaction and pore blockage effects, but correlates poorly with those of the micropore and small pore, causing the shale porosity decreases as it increases. While, the brittle mineral can promote the mesopore and macropore development, and is conducive to the micropore and small pore maintenance when its content is higher than 45%. As a result, the shale porosity tends to increase with the brittle mineral content. This study is helpful to clarify the coal measure shale gas enrichment law in the block, and provides fundamental supports for the coal measure gas efficient development.