石油与天然气地质 ›› 2018, Vol. 39 ›› Issue (2): 373-383.doi: 10.11743/ogg20180216

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低阶煤吸附孔特征及分形表征

周三栋1, 刘大锰1, 蔡益栋1, 姚艳斌1, 焦永艳2, 任世君3   

  1. 1. 中国地质大学(北京) 能源学院, 北京 100083;
    2. 中地宝联(北京)国土资源勘查技术有限公司, 北京 100193;
    3. 中国石油 青海油田公司 采油三厂, 青海 816400
  • 收稿日期:2017-04-15 修回日期:2018-02-20 出版日期:2018-04-28 发布日期:2018-05-16
  • 通讯作者: 刘大锰(1965-),男,教授、博士生导师,煤层气地质与开发。E-mail:Email:dmliu@cugb.edu.cn。 E-mail:Email:dmliu@cugb.edu.cn
  • 第一作者简介:周三栋(1991-),男,博士研究生,煤储层物性。E-mail:sandongzhou@163.com。
  • 基金项目:
    国家自然科学基金项目（41772160；41602170）；国家科技重大专项（2016ZX05043-001）；中央高校基本科研业务专项基金项目（2652017302）。

Characterization and fractal nature of adsorption pores in low rank coal

Zhou Sandong1, Liu Dameng1, Cai Yidong1, Yao Yanbin1, Jiao Yongyan2, Ren Shijun3   

  1. 1. School of Energy Resources, China University of Geosciences(Beijing), Beijing 100083, China;
    2. Zhong Di Bao Lian(Beijing) Land & Resource Exploration Technology Co., Ltd., Beijing 100193, China;
    3. No.3 Oil Extraction Factory, Qinghai Oil Field Company, PetroChina, Qinghai 816400, China
  • Received:2017-04-15 Revised:2018-02-20 Online:2018-04-28 Published:2018-05-16

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摘要： 采集8个具代表性的不同宏观煤岩类型的低阶煤岩进行了低温液氮吸附和甲烷等温吸附实验，探讨了低阶煤的吸附孔特征，确定了适合低阶煤吸附孔隙分形模型及分形维数与孔结构、吸附性能的关联性。由此将低阶煤的吸/脱附曲线划为四类并对应4种孔隙，光亮型煤中主要为一端封闭的锥形孔，半亮型煤中主要为墨水瓶状孔，半暗型煤包含了开放型的圆筒状孔和一端封闭的尖劈形孔，暗淡型煤则以开放型的圆筒状孔为主。结果表明，FHH模型相对BET模型分形较符合低阶煤孔隙特征；FHH中不同宏观煤岩类型在相对压力0 ~ 0.5 和0.5 ~ 1.0吸附特征各异得到分维数D21和D22，其中D21表征煤吸附孔表面粗糙度而D22表征吸附孔结构不规则性；D21越高，孔比表面积越大，D22越高，平均孔径越小，微孔含量越高，孔隙非均质性愈强；D21较D22对低阶煤的吸附性能控制作用大，表现为高D21低D22时，吸附能力最大，累计比表面积分维数增高，吸附能力增大。因此，低阶煤的吸附过程随压力增大为单分子层过渡到多分子层吸附为主。

关键词: 比表面积, FHH模型, 低温液氮吸附, 分形维数, 孔结构, 低阶煤

Abstract: We collected 8 kinds of low rank coal (LRC) with distinguished macrolithotypes,carried out some experiments like the low-temperature liquid nitrogen adsorption and isothermal methane adsorption,discussed the LRC adsorption pore characteristics,and established the relationship between fractal model suitable for LRC adsorption pores and fractal dimension with pore structures and adsorption capacities.From this,the LRC absorption/desorption curves are divided into four categories with 4 corresponding pore types:taper-shaped pores with one end closed being dominant in bright coal,ink-bottle-shaped pores dominating semi-bright coal,open-cylindric pores and wedge-shaped ones occurring in semidull coal,and open-cylindric pores being predominant in dull coal.Results show that (1) compared with the BET model,the FHH model is more appropriate for the characterization of LRC pores in respect of fractal nature;(2) the various macrolithotypes in FHH model show different adsorption characteristics at relative pressure 0~0.5 and 0.5~0.5 and have fractal dimensions D21 and D22 respectively,with D21 representing the surface roughness of adsorption pores and D22 the irregularity of the pore structures.As D21 gets bigger,the pore specific surface area increases,whereas the bigger D22 gets,the smaller the average pore size becomes,the higher the micropore content is,and the larger the pore heterogeneity is;(3) D21 is more effective than D22 in controlling the adsorption capacity of LRC.When the coal is characterized by high D21 and low D22,the adsorption capacity is the strongest,and the adsorption capacity enlarges as the fractal dimension of cumulative specific surface area increases.The LRC adsorption process subsequently shows transition from predominance of monomolecular layer adsorption to predominance of polymolecular layer adsorption with increasing pressure.

Key words: specific surface area, FHH model, low-temperature liquid nitrogen adsorption, fractal dimension, pore structure, LRC

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