DataSheet3_Effect of disturbed coal pore structure on gas adsorption characteristics: mercury intrusion porosimetry.xlsx

Studying pore structures of disturbed coal and their influences on adsorption characteristics is conducive to in-depth understanding of occurrence and migration of gas in reservoirs in areas prone to coal and gas outbursts. A mercury porosimeter and a high-pressure gas adsorption instrument were separately used to investigate pore structures and measure adsorption characteristics of disturbed coal and undisturbed coal in Ningtiaota Coal Mine and Xigu Coal Mine (Shaanxi Province, China). In addition, pore structures and gas adsorption characteristics of coal samples were studied. The Menger’s sponge model was adopted to calculate fractal dimensions of coal samples, to estimate influences of pore structures and fractal features on the gas adsorption characteristics of disturbed and undisturbed coal. Results show that the pore volume of undisturbed coal is mainly contributed by micropores and transitional pores, while that of disturbed coal arises mainly from macropores and mesopores. Micropores and transitional pores account for large proportions of the specific surface area of pores in both disturbed and undisturbed coal. The adsorption isotherms of disturbed and undisturbed coal conform to the Langmuir equation and tectonism increases the limiting adsorption quantity of coal. The fractal dimensions D1 of the four types of coal samples in the experiments are in the range of 2.7617–2.9961, while the fractal dimensions D1 and D2 of disturbed coal are both larger than those of undisturbed coal, indicating that disturbed coal is more likely to collapse under high pressure. The total pore volume, total specific surface area of pores, and fractal dimensions are positively correlated with the adsorption constant a, while they have U-shaped correlations with the adsorption constant b of coal samples. The adsorption constant a of disturbed coal is always greater than that of undisturbed coal, while no obvious trend is observed between the adsorption constant b and tectonism. The research results can provide theoretical basis for further study of gas occurrence in disturbed coal seams.

探究受扰动煤体的孔隙结构及其对吸附特性的影响，有助于深入理解煤与瓦斯突出易发区域储层中瓦斯的赋存与运移规律。本研究分别采用压汞仪（mercury porosimeter）与高压气体吸附仪，对中国陕西省柠条塔煤矿与西固煤矿的受扰动煤体及原生煤体的孔隙结构与吸附特性开展测试与表征。此外，本研究还针对煤样的孔隙结构与瓦斯吸附特性展开研究，采用孟杰海绵模型（Menger’s sponge model）计算煤样的分形维数，以此分析孔隙结构与分形特征对受扰动及原生煤体瓦斯吸附特性的影响机制。研究结果表明：原生煤体的孔隙体积主要由微孔与过渡孔贡献，而受扰动煤体的孔隙体积则以大孔与中孔为主。受扰动与原生煤体的孔隙比表面积均以微孔与过渡孔占比最高。受扰动与原生煤体的吸附等温线均符合朗缪尔方程（Langmuir equation），且构造扰动作用可提升煤体的极限吸附量。本次实验中四类煤样的分形维数D1取值范围为2.7617~2.9961，且受扰动煤体的分形维数D1与D2均大于原生煤体，这表明受扰动煤体在高压环境下更易发生结构坍塌。煤样的总孔隙体积、总孔隙比表面积及分形维数均与吸附常数a呈正相关关系，而与吸附常数b则呈U型相关关系。受扰动煤体的吸附常数a始终大于原生煤体，但吸附常数b与构造扰动作用之间未呈现明显的变化趋势。本研究成果可为受扰动煤层瓦斯赋存规律的后续研究提供理论依据。