过渡相煤系泥页岩纳米级孔隙结构非均质性表征及主控因素——以淮南煤田二叠系为例-《地球科学与环境学报》

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Title:: Heterogeneity Characterization and Main Control Factors of Nanoscale Pore Structure of the Transitional Coal Measures Shale—A Case Study of Permian in Huainan Coalfield

文章编号:: 1672-6561(2018)04-0449-13

作者:: 邵春景; 屈争辉; 尹宏伟; 左兆喜; 余坤; 余可龙; 1.南京大学地球科学与工程学院，江苏南京 210023； 2.中国矿业大学资源与地球科学学院，江苏徐州 221116； 3.中国科学院大学地球与行星科学学院，北京 100049

Author(s):: SHAO Chun-jing; QU Zheng-hui; YIN Hong-wei; ZUO Zhao-xi; YU Kun; YU Ke-long; 1. School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, Jiangsu, China; 2. School of Resources and Geosciences, China University of Mining and Technology, Xuzhou 221116, Jiangsu, China; 3. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China

关键词:: 海陆过渡相; 煤系泥页岩; 孔隙结构; FHH分形模型; 非均质性; 主控因素; 二叠系; 淮南煤田

Keywords:: transitional facies; coal measures shale; pore structure; FHH fractal model; heterogeneity; main control factor; Permian; Huainan coalfield

分类号:: P618.13;TE122

DOI:: -

文献标志码:: A

摘要:: 纳米级孔隙是煤系页岩气赋存的重要场所，具有很强的非均质性。为了研究海陆过渡相煤系泥页岩储层孔隙结构非均质性，对淮南煤田二叠系山西组和下石盒子组泥页岩钻孔岩芯样品进行总有机碳、镜质体反射率、全岩和黏土X射线衍射分析、场发射扫描电镜及低温液氮吸附实验，获得泥页岩有机地球化学、矿物组分、孔隙结构参数，采用孔隙结构相对偏差、FHH分形模型来评价储层孔隙结构非均质性及主控因素。结果表明：储层孔隙类型以黏土矿物片层间的平行板状孔、狭缝状孔及粒间的锥状孔为主，孔隙尺度主要为介孔，其次为微孔和宏孔；孔隙结构具显著分段分形特征，由于与煤储层高度相似而划分为渗透孔隙(r＞7.5 nm)和吸附孔隙(r≤7.5 nm)，渗透孔隙复杂程度强于吸附孔隙；微孔越发育，孔容越小，比表面积越大，分形维数越大，孔隙结构越复杂，非均质性越强；过渡相煤系泥页岩储层孔隙结构非均质性主要受控于不同沉积环境及成岩演化下矿物组分差异，随着黏土矿物含量的增加和脆性矿物含量的减小而增大；与下石盒子组相比，山西组黏土矿物含量更低，导致分形维数较低，孔隙结构复杂程度偏弱，比表面积和平均孔径的相对偏差较小，孔隙分布较均匀，非均质性相对弱，对页岩气的储存、解吸和扩散更有利，可考虑优先开采。

Abstract:: Nanoscale pores are important place for storage of coal measures shale gas, and have very strong heterogeneity. In order to study the heterogeneity of the pore structure of transitional coal shale, the core shale samples of Permian Shanxi Formation and Lower Shihezi Formation in Huainan coalfield were tested in total organic carbon, vitrinite reflectance, X-ray diffraction analysis of whole rock and clay, field emission scanning electron microscopy, and low-temperature liquid nitrogen adsorption experiment. The parameters of shale, such as organic geochemistry, mineral composition and content and pore structure were acquired, then selecting the relative deviation and FHH fractal model to quantitatively evaluate and analyze the heterogeneity and main controlling factors of shale reservoir pore structure. The results show that the reservoir mainly develops parallel plate-like pores and slit-like pores between lamella of clay minerals, and conical pores between particles of clay minerals; the pore size is dominated by mesopores, followed by micropores and the macropores; the pore structure has obvious fractal characteristics, which is divided into permeability pore (r＞7.5 nm) and adsorption pore (r≤7.5 nm) because of the similarity to the coal reservoir, and the permeability is more complex than that of adsorption pores; the more developed the micropores, the smaller the pore volume, the larger the surface area, the larger the fractal dimension, the more complex the pore structure, and the stronger the heterogeneity; the heterogeneity of pore structure of transitional coal shale reservoir is mainly controlled by the difference of mineral composition under different sedimentary environments and diagenetic evolution, and the heterogeneity increases with the increase of the clay minerals contents and the decrease of brittle mineral contents; compared with Lower Shihezi Formation, Shanxi Formation has lower clay minerals contents, leading to lower fractal dimension, weaker pore structure complexity, relative smaller deviation of specific surface area and average pore size, relatively uniform pore distribution, and relatively weak heterogeneity, thus, Shanxi Formation is more favorable for the storage, desorption and diffusion of shale gas, and the exploitation of shale gas may be considered to give priority.

《地球科学与环境学报》[ISSN:1672-6561/CN:61-1423/P]

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