海相油气地质2024，Vol.29Issue(2)：113-124,12.DOI:10.3969/j.issn.1672-9854.2024.02.001
基于液氮吸附实验的高阶煤微观孔隙结构特征研究
Microscopic pore structure characteristics of high rank coal based on liquid nitrogen adsorption experiment:a case study of the Upper Permian Leping Formation in Junlian area,south Sichuan Basin
摘要
Abstract
Junlian area in the south of Sichuan Basin,as the first commercial production base of coalbed methane in South China,has a gas producing bed in the Upper Permian Leping Formation,it is great to study the characteristics of micropore structure to analyze the characteristics of coalbed methane accumulation.In this paper,a large number of Upper Permian Leping coal samples are selected from coalbed methane evaluation wells for scanning electron microscope observation and liquid nitrogen adsorption experiments.The characteristics of pore development at micro and nano scale have been systematically analyzed from the aspects of pore genetic type,pore structure,pore morphology and methane adsorption performance.The results show that micropores of coal are divided into four genetic types:plant tissue pore,stoma,mineral mold hole and intercrystalline pore.Through quantitative analysis of pore structure parameter,it is concluded that the average BET total pore specific surface area is 2.638 m2/g,and the average BJH total pore volume is 0.003 7 cm3/g,and there is a good positive correlation between total pore specific surface area and total pore volume.The average BJH pore diameter is 5.775～17.842 nm,and the major contribution to the total specific surface area is from pores with an aperture less than 5 nm,while the major contribution to the total pore volume is from pores greater than 10 nm.According to the diameter of pores,the pore types are divided into four categories:micropore(＜5 nm),tiny pore(5～10 nm),mesopore(10～100 nm)and macropore(≥100 nm).Micropores and tiny pores are the main spaces for gas adsorption in high rank coal,and it is further concluded that the boundary value of pore diameter between adsorption pores and free pores of high rank coal is 10 nm.Nitrogen adsorption loops are divided into three types(overlap type,semi-separation and semi-overlap slow drop type,semi-separation and semi-overlap plunge type),and according to the characteristics of the loops,the nanoscale pore morphology is idealized as three typical models,namely open pore,semi-closed pore and inkbottle-shape pore,and all kinds of pores are developed in the high rank coal.Based on the comparison of isothermal adsorption experiments of methane from dry ash free coal samples with different pore morphology,it is found that the adsorption capacity of methane is the highest in inkbottle-shape pores,and the adsorption capacity of semi-closed and open holes is similar but lower than that of inkbottle-shape pores.关键词
煤层气/高阶煤/液氮吸附实验/孔隙结构/成因类型/二叠系/筠连地区Key words
coalbed methane/high rank coal/liquid nitrogen adsorption experiment/pore morphology/genetic type/Permian/Jun-lian area分类
能源科技引用本文复制引用
段洋利,梁兴,何方雨,周芸,邹辰,梅珏,张涵冰,李磊,叶璁琛..基于液氮吸附实验的高阶煤微观孔隙结构特征研究[J].海相油气地质,2024,29(2):113-124,12.基金项目
本文受中国石油天然气股份有限公司科学研究与技术开发项目"煤层气新区新层系新领域战略与评价技术研究"(编号:2021DJ2303)资助 （编号:2021DJ2303）
