脆性变形序列构造煤纳米孔隙和粗糙度的原子力显微镜研究

张宁远; 姚素平

doi:10.12363/issn.1001-1986.21.09.0500

脆性变形序列构造煤纳米孔隙和粗糙度的原子力显微镜研究

doi: 10.12363/issn.1001-1986.21.09.0500

张宁远,
姚素平^,

基金项目: 国家自然科学基金面上项目(42072152)

详细信息

第一作者:
张宁远，1998年生，男，湖北仙桃人，硕士研究生，研究方向为非常规油气储层. E-mail：m15908619262@163.com

通信作者:
姚素平，1965年生，男，安徽无为人，博士，教授，从事有机地球化学和有机岩石学研究. E-mail：spyao@nju.edu.cn

中图分类号: TE122
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- 被引次数: 0
出版历程
- 收稿日期: 2021-09-14
- 修回日期: 2021-10-14
- 录用日期: 2022-03-18
- 发布日期: 2022-05-25
- 网络出版日期: 2022-05-05

Nanopore structure and surface roughness in brittle tectonically deformed coals explored by atomic force microscopy

ZHANG Ningyuan,
YAO Suping^,

摘要

摘要: 煤孔隙结构是煤层气勘探开发与煤矿安全研究中的关键问题之一。构造煤相比于原生结构煤非均质性强，是煤储层研究中的热点和难点。采用原子力显微镜，结合NanoScope Analysis和Gwyddion分析软件，对脆性变形序列构造煤的孔隙结构和表面粗糙度特征进行研究。结果表明：构造作用整体上促进了脆性变形煤孔隙的发育，但不同脆性变形构造煤受构造作用影响的程度存在明显差异。根据煤受构造作用影响的程度，脆性变形煤孔隙结构演化可划分为强弱2个阶段：弱脆性变形阶段(原生结构煤—碎裂煤—片状煤—碎斑煤)构造作用对煤体的孔隙结构影响较小，平均孔数量缓慢增长，平均孔径缓慢减小，该阶段构造作用主要促进了100~200 nm大孔的发育；强脆性变形阶段(碎斑煤—碎粒煤—薄片煤)构造作用对煤体孔隙结构产生了显著影响，平均孔数量迅速增长，平均孔径迅速减小，这一阶段构造作用主要促进了10~50 nm介孔和50~100 nm大孔的发育。这表明脆性变形构造煤孔隙结构并非简单的线性演变。不同脆性变形煤的算术平均粗糙度和均方根粗糙度参数分别为3.00~6.05 nm和3.94~7.62 nm，其中，弱脆性变形阶段粗糙度整体较高且无明显变化，而强脆性变形阶段粗糙度迅速降低。通过AFM剖面分析，建立了煤表面孔隙形态的数学模型。基于该模型的算术平均粗糙度模拟结果表明，大孔是煤表面粗糙度的主要贡献者，构造作用主要通过影响煤中的孔隙结构，进而影响煤的表面粗糙度。
- 孔隙结构 /
- 表面粗糙度 /
- 构造煤 /
- 原子力显微镜 /
- 脆性变形 /
- 孔径分布
Abstract: The pore structure of coal is the key to coalbed methane (CBM) exploration and exploitation, and coal mining safety. Compared to primary coals, tectonically deformed coals (TDCs) have stronger heterogeneity and are of great importance in coal reservoir study. Here, the pore structure and surface roughness of brittle TDCs were obtained with atomic force microscopy (AFM) and NanoScope Analysis and Gwyddion software. The results show that tectonic deformation generally promotes the pore development in brittle TDCs, but the extent of tectonic impact varies greatly among different brittle TDCs. As a result, two stages in brittle TDCs were identified: weak brittle deformation stage (primary coal, cataclastic coal, schistose coal and mortar coal) and strong brittle deformation stage (mortar coal, granulitic coal and flaky coal). In the weak brittle deformation stage, tectonic stress has little impact on coals’ pore structure. The mean pore number increases slowly and the mean pore size decreases slowly. In this stage, the tectonic process mainly promotes the development of 100-200 nm macropores. In the strong brittle deformation stage, tectonic stress has a major impact on coals’ pore structure. The mean pore number increases quickly and the mean pore size decreases quickly. The tectonic process in this stage mainly promotes the development of mesopores of 10-50 nm and macropores of 50-100 nm. The two different tectonic stages demonstrate that the whole brittle TDCs do not evolve linearly with tectonic deformation. The arithmetical average height (R_a) and root-mean-square (R_q) roughness are 3.00-6.05 nm and 3.94-7.62 nm respectively. The weak brittle TDCs’ R_a and R_q fluctuate slightly, while the strong brittle TDCs’ R_a and R_q decrease fast. A mathematical model of the morphology of pores in the coal surface was established based on AFM sectional analysis. The R_a simulation of coal samples based on this model shows that pores of larger diameter are mainly responsible for surface roughness. R_a and R_q of coal samples are controlled mainly by nanopore development during tectonic deformation.
- pore structure /
- surface roughness /
- tectonically deformed coal /
- atomic force microscopy /
- pore size distribution /
- brittle deformation

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图 1 样品宏−微观变形特征

(a)、(b) 样号WG-6，原生结构煤；(c)、(d) 样号WG-4，碎裂煤；(e)、(f) 样号QYZ-70，片状煤；(g)、(h) 样号RL-2，碎斑煤；(i)、(j) 样号QD-3，碎粒煤；(k)、(l) 样号QYZ-86，薄片煤；(a)、(c)、(e)、(g)、(i)、(k)为样品的手标本照片；(b)、(d)、(f)、(h)、(j)、(l)为样品的显微镜反射光照片，×50

Fig. 1 Micro and macro deformation characteristics of coal samples

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图 2 Watershed法识别AFM图像中的孔隙

Fig. 2 Pores marked by the Watershed method

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图 3 不同构造煤的AFM图像

(a) 样号WG-6，原生结构煤；(b) 样号WG-4，碎裂煤；(c) 样号QYZ-70，片状煤；(d) 样号RL-2，碎斑煤；(e) 样号QD-3，碎粒煤；(f) 样号QYZ-86，薄片煤；扫描面积均为5 μm×5 μm，扫描点数均为512×512

Fig. 3 Typical AFM images of coal samples

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图 4 平均孔数量和平均孔径与构造变形程度之间的关系

Fig. 4 Relationships between the number of mean pores and mean pore size and tectonic deformation degree

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图 5 样品的孔径分布

Fig. 5 Pore size distribution of coal samples

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图 6 基于AFM的样品累积孔面积

Fig. 6 Total pore surface area of coal samples based on AFM

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图 7 基于氮气吸附的构造煤累积比表面积^[24-26]

Fig. 7 Total specific surface area of different brittle tectonic deformed coals^[24-26]

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图 8 R_a和R_q与构造变形程度之间的关系

Fig. 8 Relationships between R_a and R_q and tectonic deformation degree

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图 9 不同大小孔隙的几何模型

Fig. 9 Mathematical models of pores of different radius

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图 10 AFM图像的剖面分析

(a) 样号WG-6，原生结构煤；(b) 样号QYZ-70，片状煤；(c) 样号QD-3，碎粒煤；剖面位置如图3a、图3c、图3e所示

Fig. 10 Sectional analysis of AFM images

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表 1 样品基本信息

Table 1 General information of coal samples

样品号	构造煤类型	采样地	地层代号	R_ran/%	显微组分体积分数/%
样品号	构造煤类型	采样地	地层代号	R_ran/%	镜质组	惰质组	壳质组	矿物
WG-6	原生结构煤	五沟煤矿	P₁s	1.22	88.7	3.1	0.5	7.7
WG-4	碎裂煤	五沟煤矿	P₁s	1.16	79.8	15.7	1.0	3.5
QYZ-70	片状煤	钱营孜煤矿	P₂ss	1.01	60.6	30.0	8.7	0.7
RL-2	碎斑煤	任楼煤矿	P₂x	0.93	98.3	1.1	0.6	0
QD-3	碎粒煤	祁东煤矿	P₂x	1.10	95.0	1.1	2.2	1.7
QYZ-86	薄片煤	钱营孜煤矿	P₂ss	1.03	88.4	6.3	3.7	1.6

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表 2 样品孔隙结构参数

Table 2 Nanopore structural parameters of coal samples

样品号	R_ran/ %	平均孔数量	平均孔径/nm	平均孔面积/nm²	面孔率/ %
WG-6	1.22	86	131.4	24660	8.13
WG-4	1.16	171	125.7	24950	16.27
QYZ-70	1.01	208	115.4	20230	16.79
RL-2	0.93	245	107.7	15870	15.55
QD-3	1.10	455	87.2	9410	17.06
QYZ-86	1.03	685	68.8	5840	15.93

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表 3 样品表面粗糙度参数

Table 3 Surface roughness statistics of coal samples

样品号	粗糙度参数
样品号	R_a/nm	R_q/nm	R_sk	R_ku
WG-6	4.33±1.33	5.87±1.59	−0.75±0.55	5.26±1.37
WG-4	5.94±0.72	7.53±0.83	−0.29±0.17	3.24±0.39
QYZ-70	4.79±0.78	6.22±1.00	−0.56±0.22	3.75±0.54
RL-2	6.02±0.69	7.58±0.81	−0.39±0.25	3.19±0.48
QD-3	5.01±0.60	6.31±0.77	0.03±0.09	3.12±0.30
QYZ-86	3.00±0.30	3.98±0.42	−0.45±0.26	4.80±1.44
注：粗糙度参数以平均值±标准差的形式表示。

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