榆社-武乡区块煤储层孔隙结构特征及其影响因素分析
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摘要
为研究低孔低渗煤储层制约煤层气井高产的原因,以沁水盆地中东部榆社-武乡区块山西组和太原组煤储层为研究对象,采用扫描电镜电子成像技术和低温液氮吸附试验分析方法,研究探讨了煤储层孔隙结构特征及其影响因素。结果表明:研究区煤储层纳米级孔隙多发育在镜质组中,少数发育在惰质组中,以变质成因孔最为常见,亦发育原生孔和矿物质孔;孔隙形态以墨水瓶形孔和狭缝形孔为主;煤储层平均比表面积1.342 9 m2/g,平均孔容0.005 0 cm3/g,平均孔径15.744 2 nm,孔隙系统渗流能力较差。随着变质程度加深和镜质组百分含量增加,比表面积呈现出简单的递增趋势;而孔容、孔径最重要的影响因素为煤体结构,碎裂煤的孔容和孔径要明显高于原生结构煤。
To study the reasons for controlling high productivity of coalbed methane wells in low porosity and low permeability coal reservoirs,the coal reservoirs of Shanxi and Taiyuan Formations in Yushe-Wuxiang Block located in the central and eastern Qinshui Basin were studied. The pore structure characteristics and influencing factors of coal reservoirs were studied and analyzed by scanning electron microscopy( SEM) electronic imaging technology and the cryogenic liquid nitrogen adsorption experiment. The results show that the nanoscale pores of coal reservoirs mostly developed in the vitrinite group while a few of them developed in the inverting group. Among them,the metamorphic pore is the most widely encountered. The protogenetic pores and mineral pores also developed. The pore morphology is mainly ink-bottle holes and slit holes. The average specific surface area of coal reservoir is 1.342 9 m2/g,and the average pore volume is 0.005 0 cm3/g. Additionally,the average pore diameter is 15.744 2 nm. The influent capacity of pore system is poor. The contribution of specific surface area is dominated by micropores. The specific surface area shows a simple increasing trend as the metamorphism deepened and the percentage content of the vitrinite increased. However,the coal structure is the most important factor in influencing the pore volume and pore diameter. The pore volume and pore diameter of fractured coal are apparently higher than that of the protogenetic coal.
To study the reasons for controlling high productivity of coalbed methane wells in low porosity and low permeability coal reservoirs,the coal reservoirs of Shanxi and Taiyuan Formations in Yushe-Wuxiang Block located in the central and eastern Qinshui Basin were studied. The pore structure characteristics and influencing factors of coal reservoirs were studied and analyzed by scanning electron microscopy( SEM) electronic imaging technology and the cryogenic liquid nitrogen adsorption experiment. The results show that the nanoscale pores of coal reservoirs mostly developed in the vitrinite group while a few of them developed in the inverting group. Among them,the metamorphic pore is the most widely encountered. The protogenetic pores and mineral pores also developed. The pore morphology is mainly ink-bottle holes and slit holes. The average specific surface area of coal reservoir is 1.342 9 m2/g,and the average pore volume is 0.005 0 cm3/g. Additionally,the average pore diameter is 15.744 2 nm. The influent capacity of pore system is poor. The contribution of specific surface area is dominated by micropores. The specific surface area shows a simple increasing trend as the metamorphism deepened and the percentage content of the vitrinite increased. However,the coal structure is the most important factor in influencing the pore volume and pore diameter. The pore volume and pore diameter of fractured coal are apparently higher than that of the protogenetic coal.
引文
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[17]段旭琴,曲剑午,王祖讷.低变质烟煤有机显微煤岩组分的孔结构分析[J].中国矿业大学学报,2009,38(2):224-228.DUAN Xuqin,QU Jianwu,WANG Zune. Pore structure of macerals from a low rank bituminous[J].Journal of China University of Mining&Technology,2009,38(2):224-228.
[2]许浩,张尚虎,冷雪,等.沁水盆地煤储层孔隙系统模型与物性分析[J].科学通报,2005,50(S1):45-50.XU Hao,ZHANG Shanghu,LENG Xue,et al. Pore system model and physical property analysis of coal reservoir in Qinshui Basin[J]. Chinese Science Bulletin,2005,50(S1):45-50.
[3]赵兴龙,汤达祯,许浩,等.煤变质作用对煤储层孔隙系统发育的影响[J].煤炭学报,2010,35(9):1506-1511.ZHAO Xinglong,TANG Dazhen,XU Hao,et al. Effect of coal metamorphic process on pore system of coal reservoirs[J]. Journal of China Coal Society,2010,35(9):1506-1511.
[4]许启鲁,黄文辉,唐书恒,等.深部中-高煤级煤储层孔隙结构与吸附性[J].现代地质,2016,30(2):413-419.XU Qilu,HUANG Wenhui,TANG Shuheng,et al. Pore structure and adsorption of deep medium-high rank coal reservoirs[J]. Geosciences,2016,30(2):413-419.
[5]李俊乾,姚艳斌,蔡益栋,等.华北地区不同变质程度煤的物性特征及成因探讨[J].煤炭科学技术,2012,40(4):111-115.LI Junqian,YAO Yanbin,CAI Yidong,et al. Discussion on coal physical properties and formation with different metamorphic degree in North China[J]. Coal Science and Technology,2012,40(4):111-115.
[6]吴见,汤达祯,李松,等.鄂尔多斯盆地东缘煤储层孔隙结构特征差异及影响因素[J].煤田地质与勘探,2017,45(5):59-65.WU Jian,TANG Dazhen,LI Song,et al. Characteristics and influence factors of pore structure of coal reservoirs in the eastern margin of Ordos basin[J]. Coal Geology&Exploration,2017,45(5):59-65.
[7]孟召平,刘珊珊,王保玉,等.不同煤体结构煤的吸附性能及其孔隙结构特征[J].煤炭学报,2015,40(8):1865-1870.MENG Zhaoping,LIU Shanshan,WANG Baoyu,et al. Adsorption capacity and its pore structure of coals with different coal body structure[J]. Journal of China Coal Society,2015,40(8):1865-1870.
[8]李明,姜波,秦勇,等.构造煤中矿物质对孔隙结构的影响研究[J].煤炭学报,2017,42(3):727-731.LI Ming,JIANG Bo,QIN Yong,et al. Analysis of mineral effect on coal pore structure of tectonically deformed coal[J]. Journal of China Coal Society,2017,42(3):727-731.
[9]张慧.煤孔隙的成因类型及其研究[J].煤炭学报,2001,26(1):40-44.ZHANG Hui. Genetical type of proes in coal reservoir and its research significance[J]. Journal of China Coal Society,2001,26(1):40-44.
[10]任会康,王安民,李昌峰,等.基于核磁共振技术的低阶煤储层孔隙特征研究[J].煤炭科学技术,2017,45(4):143-148.REN Huikang,WANG Anmin,LI Changfeng,et al. Study on porosity characteristics of low-rank coal reservoirs based on nuclear magnetic resonance technology[J]. Coal Science and Technology,2017,45(4):143-148.
[11]谢松彬,姚艳斌,陈基瑜,等.煤储层微小孔隙结构的低场核磁共振研究[J].煤炭学报,2015,40(S1):170-176.XIE Songbin,YAO Yanbin,CHEN Jiyu,et al. Research of micropore structure in coal reservoir using low-field NMR[J]. Journal of China Coal Society,2015,40(S1):170-176.
[12]杨光,秦勇,吴财芳,等.新疆和什托洛盖盆地西山窑组低阶煤孔隙结构特征[J].煤炭科学技术,2017,45(4):123-130.YANG Guang,QIN Yong,WU Caifang,et al. Pore structure features of Xishanyao Formation low rank coal in Hoxtolgay Basin of Xinjiang[J]. Coal Science and Technology, 2017, 45(4):123-130.
[13]陈萍,唐修义.低温氮吸附法与煤中微孔隙特征的研究[J].煤炭学报,2001,26(5):552-556.CHEN Ping,TANG Xiuyi. The research on the adsorption of nitrogen in low temperature and micro-pore properties in coal[J].Journal of China Coal Society,2001,26(5):552-556.
[14]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].煤炭科学技术,2017,45(5):75-81.HOU Jinxiu,WANG Baojun,ZHANG Yugui,et al. Evolution characteristics of micro-pore and meso-pore of different rank coal and cause of their formation[J]. Coal Science and Technology,2017,45(5):75-81.
[15]王乔,赵东,冯增朝,等.基于CT扫描的煤岩钻孔注液氮致裂试验研究[J].煤炭科学技术,2017,45(4):149-154.WANG Qiao,ZHAO Dong,Feng Zengchao,et al. Experimental study on fracturing of coal by injection liquid nitrogen in drill based on CT scanning[J]. Coal Science and Technology,2017,45(4):149-154.
[16]刘大锰,姚艳斌,蔡益栋,等.华北石炭-二叠系煤的孔渗特征及主控因素[J].现代地质,2010,24(6):1198-1203.LIU Dameng,YAO Yanbin,CAI Yidong,et al. Characteristics of porosity and permeability and their geological control of PermoCarboniferous coals in North China[J]. Geosciences,2010,24(6):1198-1203.
[17]段旭琴,曲剑午,王祖讷.低变质烟煤有机显微煤岩组分的孔结构分析[J].中国矿业大学学报,2009,38(2):224-228.DUAN Xuqin,QU Jianwu,WANG Zune. Pore structure of macerals from a low rank bituminous[J].Journal of China University of Mining&Technology,2009,38(2):224-228.