基于原子力显微镜的煤岩微观孔隙结构与力学性质研究

Study on microscopic pore structures and mechanical properties of coal using atomic force microscopy

赵石虎 李勇 刘雅利 王延斌 刘曾勤 陈刚 陈新军

ZHAO Shihu LI Yong LIU Yali WANG Yanbin LIU Zengqin CHEN Gang CHEN Xinjun

1. 页岩油气富集机理与高效开发全国重点实验室, 北京 102206; 2. 中国石化 页岩油气勘探开发重点实验室, 北京 102206; 3. 中国石化 深层煤层气勘探开发重点实验室, 北京 102206; 4. 中国石化 石油勘探开发研究院, 北京 102206; 5. 中国矿业大学(北京), 北京 100083

1. State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 102206, China; 2. SINOPEC Key Laboratory of Shale Oil and Gas Exploration and Production, SINOPEC, Beijing 102206, China; 3. SINOPEC Key Laboratory of Deep Coalbed Methane Exploration and Development, Beijing 102206, China; 4. SINOPEC Petroleum Exploration and Production Research Institute, Beijing 102206, China; 5. China University of Mining and Technology (Beijing), Beijing 100083, China

煤岩孔隙结构与力学性质是煤层气地质评价的关键参数，反映煤的储集性与可压性。以山西沁水、大同等盆地4块煤样(大同侏罗系煤、镜质体反射率Ro=0.91%，古交山西组2号煤、Ro=1.34%，古交太原组8号煤、Ro=1.70%，翼城山西组2号煤、Ro=1.77%)为研究对象，基于原子力显微镜实验，利用图像分割法与Derjaguin-Muller-Toporov力学模型建立微观孔隙结构与力学性质联合表征技术，明确煤样的微观孔隙结构与力学性质，揭示了物质组成、孔隙结构及热演化程度对微观力学性质的影响。结果表明，煤样的面孔率主要分布于2.72%~4.60%，平均3.58%；总孔表面积为(3.413~5.638)×10-2 μm2/μm2，总孔容为(0.5~3.9)×10-4 μm3/μm2，孔径主要分布于10~100 nm，杨氏模量分布于2.24~3.10 GPa，平均2.77 GPa。煤的力学性质受到物质组成、孔隙结构与热演化程度的共同作用，随着水分的减少、挥发分与矿物含量的增加，杨氏模量呈现增大趋势；表面粗糙度、平均孔径、面孔率、比表面积及总孔容增大，杨氏模量表现出减小趋势；随着热演化程度增加，杨氏模量减小。基于原子力显微镜可同步揭示煤岩微观孔隙结构与力学性质，为煤储层储集性与力学研究提供新方法与新思路，对于非常规储层储集性评价及可压性研究具有重要意义。

The pore structures and mechanical properties of coal are key parameters for geological evaluation of coalbed methane, reflecting its reservoir capacity and compressibility. The study investigated four coal samples from the Qinshui and Datong basins in Shanxi Province, including Jurassic coal from Datong (Ro=0.91%), No. 2 coal from the Shanxi Formation in Gujiao (Ro=1.34%), No. 8 coal of the Taiyuan Formation in Gujiao (Ro=1.70%), and No. 2 coal of the Shanxi Formation in Yicheng (Ro=1.77%). Using atomic force microscopy (AFM), a combined characterization technique was established for microscopic pore structure and mechanical properties based on image segmentation and Derjaguin-Muller-Toporov (DMT) mechanical model. This method clarified the microscopic pore structure and mechanical properties of coal samples and revealed the influence of material composition, pore structure, and thermal evolution level on their microscopic mechanical properties. The results showed that the surface porosity of coal samples mainly ranged from 2.72% to 4.60%, with an average of 3.58%. The total pore surface area and total pore volume were (3.413-5.638)×10-2 μm2/μm2 and (0.5-3.9)×10-4 μm3/μm2, respectively. The pore sizes were mainly distributed between 10-100 nm, and the Young’s modulus ranged from 2.24 to 3.10 GPa, with an average of 2.77 GPa. The mechanical properties of coal were influenced by the material composition, pore structure, and thermal evolution level. As moisture decreased and volatile and mineral content increased, the Young’s modulus showed an increasing trend. With an increase in surface roughness, mean pore size, porosity surface, specific surface area, and total pore volume, the Young’s modulus decreased. As thermal evolution progressed, the Young’s modulus decreased. AFM enables simultaneous analysis of microscopic pore structure and mechanical properties of coal, providing new methods and insights for studying reservoir capacity and mechanical behavior of coal reservoirs. It holds significant implications for the evaluation of reservoir capacity and compressibility in unconventional reservoirs.

中国石化科技部项目(P23206，P23230)和中国石化石油勘探开发研究院优青项目(YK202406)联合资助。

https://doi.org/10.11781/sysydz2025010173