Study on pore structure and fractal characteristics of shale from coal measures of Longtan Formation in western Guizhou
DENG Ende,JIANG Bingren,GAO Wei,FU Wei
为了研究煤系泥页岩微观孔隙结构特征,以黔西地区龙潭组煤系泥页岩为研究对象,基于扫描电镜及低温氮气吸附实验测试手段,定性和定量表征页岩孔隙特征,同时运用分形理论分析了其分形特征,并探讨了孔隙结构影响因素。结果表明:黔西地区龙潭组煤系泥页岩扫描电镜下观察到粒间孔、粒内孔、微裂缝及有机质孔4类,微裂缝大量发育,为烃类气体运移提供通道,仅见少量有机质孔隙;泥页岩氮气吸附等温线与Ⅳ型等温线相近,曲线均呈反“S”型,反映出主要为中孔,在高比压区(0.45<P/P0<1.0)形成滞后回线,表现为H2型的细颈广体的墨水瓶孔和H4型的狭缝型孔;孔径平均值为8.36 nm,以中孔为主,比表面积较大,平均为12.03 m2/g,总孔体积较大,平均为0.017 379 m3/g;采用FHH模型对低比压区(0<P/P0<0.45)和高比压区(0.45<P/P0<1.0)2个阶段进行计算分形维数(D1、D2),分形维数较大,D1平均为2.576 3、D2平均为2.703 2;总有机碳含量对泥页岩BET比表面积和平均孔径影响较小,与BJH总孔体积呈一定的负相关性;矿物成分对泥页岩的孔径和比表面积有较大的影响,黏土矿物含量越低、石英含量越高,平均孔径越大,石英含量越高,比表面积越小;泥页岩比表面积越大、平均孔径越小,泥页岩黏土矿物含量越高、石英含量越低,分形维数越大,煤系泥页岩孔隙结构复杂,连通性较差,非均质性较强。
In order to study the micro-pore structure characteristics of coal shale,taking the shale from coal measures of Longtan Formation in western Guizhou as the research object,based on SEM and low temperature nitrogen adsorption test,the pore characteristics are characterized qualitatively and quantitatively,meanwhile,using fractal theory analyze its fractal characteristics and the factors influencing the pore structure.The results showed that under scanning electron microscope,intergranular pores,intragranular pores,microfractures and organic pores were observed,there are a lot of microfractures,providing a channel for hydrocarbon gas migration,and only a few organic pores;the nitrogen adsorption isotherm of shale is similar to that of Type Ⅳ,the curves are all inverted S type,reflecting that it is mainly mesoporous,forming hysteresis loop in high specific pressure zone (0.45
shale of coal measures;nitrogen adsorption;pore structure;fractal theory;western Guizhou
0 引言
1 样品采集与试验方法
1.1 样品采集
1.2 试验方法
2 微观孔隙结构特征
2.1 孔隙类型
2.2 孔隙形态特征
2.3 孔径分布及孔隙结构参数
3 孔隙分形特征
4 孔隙结构影响因素分析
4.1 分形维数与孔隙结构参数的关系
4.2 分形维数与TOC及矿物成分的关系
4.3 孔隙结构参数与TOC、矿物成分的关系
5 结论
主办单位:煤炭科学研究总院有限公司 中国煤炭学会学术期刊工作委员会