基于压汞、低温N_2吸附和CO_2吸附的构造煤孔隙结构表征
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摘要
我国煤层受多期次构造运动影响构造煤普遍发育,构造煤孔隙大小分布尺度较广(毫米～纳米级),孔隙结构较为复杂。不同尺度的孔隙结构控制着煤层气的吸附-解吸(孔隙表面)、扩散(纳米级孔隙)与渗流(微米～毫米级孔隙)等过程,是影响煤层气储存与运移的重要因素。为研究构造煤不同尺度孔隙结构的分布特征与演化规律,在潞安矿区采集4种破坏类型煤样,利用压汞法、低温N_2吸附法及CO_2吸附法分别测试了煤样的孔隙分布特征,对比分析了各测试方法的优势孔径段,提出利用CO_2吸附法表征构造煤微孔(<2 nm)、低温N_2吸附法表征介孔(2～50 nm)、压汞法表征大孔结构(>50 nm)的孔隙结构多尺度联合表征方法。实验结果表明所采煤样的孔容和孔比表面积均主要分布在微孔阶段,在0. 6 nm左右时的孔隙孔容量和孔比表面积达到最大,其中微孔容占总孔容的70%以上,微孔孔比表面积占总孔比表面积的99%以上,煤中孔容和孔比表面积分布存在微孔>大孔>介孔的规律。分析构造煤孔隙特征与煤体破坏类型的关系,随煤破坏程度增加,孔容和孔比表面积逐渐增高,大孔孔容比及介孔孔容比逐渐增大,微孔孔容比逐渐减小;孔容增幅主要体现在大孔阶段,比表面积增幅则主要体现在微孔阶段。其中大孔演化主要受控于角砾孔、碎粒孔及摩擦孔等外生孔,介孔演化受控于煤的大分子堆叠结构及分子间距,微孔演化主要受控于煤中芳香层片大小及排列方式。
Tectonic coal is generally developed in China because of multi-stage tectonic movement. The pore size distribution scale of tectonic coal is wide(millimeter level-nanometer level),and the pore structure is more complex. The pore structure of different scales controls the process of adsorption-desorption( pore surface), diffusion(nanometer pores) and seepage(micron-millimeter pores) of coalbed methane. Pore structure of different scales is an important factor affecting the storage and migration of CBM. In order to study the distribution characteristics and evolution law of pore structure of tectonic coal with different scales, four kinds of destruction types of coal samples were collected in Lu'an mining area. The pore distribution characteristics of coal samples were tested by pressure mercury method,low temperature N_2 adsorption method and CO_2 adsorption method respectively. The dominant aperture segments of each test method are compared and analyzed. A method of multi-scale joint characterization of microporous structures(<2 nm) by CO_2 adsorption method,mesoporous structure(2-50 nm) by low-temperature N_2 adsorption method,and macroporous structure( >50 nm) by mercury injection method was proposed. The experimental results show that the pore capacity and pore specific surface area of coal are mainly distributed in the micro-pore stage, and the pore capacity and pore specific surface area reach the maximum at about 0.6 nm. Micropore volume accounts for more than 70%of the total pore volume,and micropore specific surface area accounts for more than 99% of the total pore specific surface area. The distribution of pore volume and pore specific surface area in coal has the rule that micropore is larger than macropore and macropore is larger than mesoporous. With the increase of coal damage degree,the pore volume and pore specific surface area gradually increase, the pore volume ratio of large pore and mesoporous pore gradually increase, and the pore volume ratio of micro pore gradually decrease. The increase of pore volume is mainly reflected in the macroporous stage,while the increase of surface area is mainly reflected in the microporous stage. Macropore evolution is mainly controlled by exogenous pores, such as brectus pore, granular pore and friction pore. Mesoporous evolution is controlled by the macromolecular stack structure and molecular spacing of coal. Micropore evolution is mainly controlled by the size and arrangement of aromatic plane in coal.
Tectonic coal is generally developed in China because of multi-stage tectonic movement. The pore size distribution scale of tectonic coal is wide(millimeter level-nanometer level),and the pore structure is more complex. The pore structure of different scales controls the process of adsorption-desorption( pore surface), diffusion(nanometer pores) and seepage(micron-millimeter pores) of coalbed methane. Pore structure of different scales is an important factor affecting the storage and migration of CBM. In order to study the distribution characteristics and evolution law of pore structure of tectonic coal with different scales, four kinds of destruction types of coal samples were collected in Lu'an mining area. The pore distribution characteristics of coal samples were tested by pressure mercury method,low temperature N_2 adsorption method and CO_2 adsorption method respectively. The dominant aperture segments of each test method are compared and analyzed. A method of multi-scale joint characterization of microporous structures(<2 nm) by CO_2 adsorption method,mesoporous structure(2-50 nm) by low-temperature N_2 adsorption method,and macroporous structure( >50 nm) by mercury injection method was proposed. The experimental results show that the pore capacity and pore specific surface area of coal are mainly distributed in the micro-pore stage, and the pore capacity and pore specific surface area reach the maximum at about 0.6 nm. Micropore volume accounts for more than 70%of the total pore volume,and micropore specific surface area accounts for more than 99% of the total pore specific surface area. The distribution of pore volume and pore specific surface area in coal has the rule that micropore is larger than macropore and macropore is larger than mesoporous. With the increase of coal damage degree,the pore volume and pore specific surface area gradually increase, the pore volume ratio of large pore and mesoporous pore gradually increase, and the pore volume ratio of micro pore gradually decrease. The increase of pore volume is mainly reflected in the macroporous stage,while the increase of surface area is mainly reflected in the microporous stage. Macropore evolution is mainly controlled by exogenous pores, such as brectus pore, granular pore and friction pore. Mesoporous evolution is controlled by the macromolecular stack structure and molecular spacing of coal. Micropore evolution is mainly controlled by the size and arrangement of aromatic plane in coal.
引文
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[19]秦勇,姜波,王超,等.中国高煤级煤的电子顺磁共振特征——兼论煤中大分子基本结构单元的“拼叠作用”及其机理[J].中国矿业大学学报,1997,26(2):10-14.QIN Yong, JIANG Bo, WANG Chao,et al. Electron paramagnetic resonance studies of high-rank coals in China:A reference to makingup and its mechanism of macromolecular basic structural units in coals[J]. Journal of China University of Mining&Technology, 1997,26(2):10-14.
[20]侯锦秀,王宝俊,张玉贵,等.不同煤级煤的微孔介孔演化特征及其成因[J].煤田地质与勘探,2017,45(5):75-81.HOU Jinxiu,WANG Baojun,ZHANG Yugui,et al. Evolution characteristics of micropore and mesopore of different rank coal and cause of their formation[J]. Coal Geology&Exploration,2017,45(5):75-81.
[21] JU Yiwen, LUXBACHER Kray,LI Xiaoshi,et al. Micro-structural evolution and their effects on physical properties in different types of tectonically deformed coals[J]. International Journal of Coal Science&Technology,2014,1(3):264-275.
[2]王聪,江成发,储伟,等.煤的分形维数及其影响因素分析[J].中国矿业大学学报,2013,42(6):1009-1014.WANG Cong, JIANG Chengfa,CHU Wei,Fractal dimension of coal and analysis of its influencing factors[J]. Journal of China Universi-ty of Mining&Techenology,2013,42(6):1009-1014.
[3]王凯,乔鹏,王壮森,等.基于二氧化碳和液氮吸附、高压压汞和低场核磁共振的煤岩多尺度孔径表征[J].中国矿业,2017,46(4):146-152.WANG Kai,QIAO Peng, WANG Zhuangsen, et al. Multiple scale pore size characterization of coal based on carbon dioxide and liquid nitrogen adsorption, high-pressure mercury intrusion and low field nuclear magnetic resonance[J]. China Mining Magazine,2017,46(4):146-152.
[4]付常青,朱炎铭,陈尚斌,等.浙西荷塘组页岩孔隙结构及分形特征研究[J].中国矿业大学学报,2016,45(1):77-86.FU Changqing,ZHU Yanming,CHEN Shangbin,et al. Pore structure and fractal features of Hetang formation shale in western Zhejiang[J]. Journal of China University of Mining&Techenology,2016,45(1):77-86.
[5] CLARKSON C R,HAGHSHENAS B,GHANIZADEH A,et al. Nanopores to megafractures:Current challenges and methods, for shale gas reservoir and hydraulic fracture characterization[J]. Journal of Natural Gas Science and Engineering,2016,31:612-657.
[6]朱炎铭,王阳,陈尚斌,等.页岩储层孔隙结构多尺度定性定量表征——以上扬子海相龙马溪组为例[J].地学前缘,2016,23(1):154-163.ZHU Yanming,WANG Yang, CHEN Shangbin, et al. Qualitativequantitative multiscale characterization of porereservoirs:A case study of Longmaxi Formation in the Upper Yangtze area[J].Earth Science Hrontiers,2016,23(1):154-163.
[7]陈燕燕,邹才能,Maria mastalerz,等.页岩微观孔隙演化及分形特征研究[J].天然气地球科学,2015,26(9):1646-1656.CHEN Yanyan,ZOU Caineng,MARIA Mastalerz,et al. Porosity and fractal characteristics of shale across a maturation gradient[J]. Natural Gas Geoscience,2015,26(9):1646-1656.
[8]曹涛涛,宋之光,刘光祥,等.氮气吸附法一压汞法分析页岩孔隙、分形特征及其影响因素[J].天然气地球科学,2013,24(3):450-455.CAO Taotao,SONG Zhiguang,LIU Guangxiang,et al. Characteristics of shale pores, fractal dimension and their controlling factors determined by nitrogen adsorption and mercury injection methods[J]. Petroleum Geology and Recovery Efficiency,2013,24(3):450-455.
[9]赵俊龙,汤达祯,许浩,等.基于二氧化碳吸附实验的页岩微孔结构精细表征[J].大庆石油地质与开发,2015,34(5):156-161.ZHAO Junlong,TANG Dazhen,XU Hao,et al. Fine characterization of the shale micropore structures based on the carbon dioxide adsorption experiment[J]. Petroleum Geology and Oilfield Development in Daqing,2015,34(5):156-161.
[10]袁崇孚.构造煤和煤与瓦斯突出[J].瓦斯地质,1985:45-52.YUAN Chongfu. Tectonic coal and coal and gas outburst[J].Gas Geology, 1985:45-52.
[11]陈义林,秦勇,田华,等.基于压汞法无烟煤孔隙结构的粒度效应[J].天然气地球科学,2015,26(9):1629-1639.CHEN Yilin,QIN Yong,TIAN Hua, et al. Particle size effect of pore structure of anthracite by mercury porosimetry[J].Natural Gas Geoscience,2015,26(9):1629-1639.
[12]张志勇,廖光伦,唐桂宾,等.压汞仪数据处理中消除水银封闭间隙体积的量化方法[J].矿物岩石,1997,17(3):50-53.ZHANG Zhiyong,LIAO Guanglun, TANG Guibin,et al. Quantitative method for eliminating mercury-locked pore volume in the course of processing data from autopore II 9220[J]. Mineral Petrol, 1997,17(3):50-53.
[13] MATTHIAS Thommes,KATSUMI Kaneko, ALEXANDER V. Physisorption of gases,with special reference to the evaluation of surface area and pore size distribution(IUPAC Technical Report)[R].PURE Appl.Chem.,2015.
[14]张哲泠,杨正红.微介孔材料物理吸附准确性分析的理论与实践[J].催化学报,2013,34(10):1797-1810.ZHANG Zheling,YANG Zhenghong. Theoretical and practical discussion of measurement accuracy for physisorption with microand mesoporous materials[J]. Chinese Journal of Catalysis,2013,34(10):1797-1810.
[15] TODA Y,TOYODA S. Application of mercury porosimetry to coal[J]. Fuel, 1972,51(3):199-201.
[16] DEBELAK K A,SCHRODT J T. Comparison of pore structure in Kentucky coals by mercury penetrate on carbon dioxide adsorption[J]. Fuel, 1979,58(10);732-736.
[17] LI Y H,LU G Q,RUDOLPH V. Compressibility and fractal dimension of fine coal particles inrelation to pore structure characterisation using mercury porosimetry[J]. Part Syst Charact, 1999,16(1):25-31.
[18]张慧.煤孔隙的成因类型及其研究[J].煤炭学报,2001,26(1):40-43.ZHANG Hui. Genetical type of proes in coal reservoir and its research significance[J]. Journal of China Coal Society, 2001,26(1):40-43.
[19]秦勇,姜波,王超,等.中国高煤级煤的电子顺磁共振特征——兼论煤中大分子基本结构单元的“拼叠作用”及其机理[J].中国矿业大学学报,1997,26(2):10-14.QIN Yong, JIANG Bo, WANG Chao,et al. Electron paramagnetic resonance studies of high-rank coals in China:A reference to makingup and its mechanism of macromolecular basic structural units in coals[J]. Journal of China University of Mining&Technology, 1997,26(2):10-14.
[20]侯锦秀,王宝俊,张玉贵,等.不同煤级煤的微孔介孔演化特征及其成因[J].煤田地质与勘探,2017,45(5):75-81.HOU Jinxiu,WANG Baojun,ZHANG Yugui,et al. Evolution characteristics of micropore and mesopore of different rank coal and cause of their formation[J]. Coal Geology&Exploration,2017,45(5):75-81.
[21] JU Yiwen, LUXBACHER Kray,LI Xiaoshi,et al. Micro-structural evolution and their effects on physical properties in different types of tectonically deformed coals[J]. International Journal of Coal Science&Technology,2014,1(3):264-275.