二氧化碳致裂对煤岩孔隙表面分形特征影响实验研究
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摘要
为了探究二氧化碳致裂对贵州高瓦斯低渗透煤层的孔隙致裂增透作用,提出了应用低温氮吸附与FHH模型相结合的方法,分析致裂前后煤样的微观孔隙特征变化,并将分形维数与孔隙特征参数结合。研究结果表明:二氧化碳致裂对煤的孔隙具有明显的作用效果,致裂后煤岩体中微孔含量、比表面积减少,而孔容、平均孔直径增加;致裂作用会使煤的分形维数减小,孔隙表面受致裂效果会趋于光滑;受二氧化碳致裂作用,分形维数的大小与平均孔直径、孔容和吸附量等存在负相关关系,与比表面积、微孔含量等呈正相关关系。
In order to explore the effect of carbon dioxide cracking on the pore cracking and permeability improvement of high-gas and low-permeability coal seams in Guizhou,a combined method of low-temperature nitrogen adsorption and fractal FHH model was proposed. The change of microscopic pore characteristics of coal samples before and after cracking was analyzed,and the fractal dimension were combined with the pore characteristic parameters. The results showed that the carbon dioxide cracking had obvious effect on the pores of coal. After the cracking,the micropore content and specific surface area of the coal and rock mass decreased,while the pore volume and average pore diameter increased. The cracking effect will reduce the fractal dimension of coal,and the pore surface would tend to be smooth due to the cracking effect. Affected by the carbon dioxide cracking,the magnitude of fractal dimension had a negative correlation with the average pore diameter,pore volume and adsorption quantity,while a positive correlation with the specific surface area and micropore content.
In order to explore the effect of carbon dioxide cracking on the pore cracking and permeability improvement of high-gas and low-permeability coal seams in Guizhou,a combined method of low-temperature nitrogen adsorption and fractal FHH model was proposed. The change of microscopic pore characteristics of coal samples before and after cracking was analyzed,and the fractal dimension were combined with the pore characteristic parameters. The results showed that the carbon dioxide cracking had obvious effect on the pores of coal. After the cracking,the micropore content and specific surface area of the coal and rock mass decreased,while the pore volume and average pore diameter increased. The cracking effect will reduce the fractal dimension of coal,and the pore surface would tend to be smooth due to the cracking effect. Affected by the carbon dioxide cracking,the magnitude of fractal dimension had a negative correlation with the average pore diameter,pore volume and adsorption quantity,while a positive correlation with the specific surface area and micropore content.
引文
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[2]王龙飞,蒋仲安,陈举师,等.低压注水对煤体孔隙特征及渗透率的影响[J].中国安全生产科学技术,2018,14(6):108-113.WANG Longfei,JIANG Zhongan,CHEN Jushi,et al. Influence of low pressure water injection on pore characteristics and permeability of coal[J]. Journal of Safety Science and Technology,2018,14(6):108-113.
[3]李希建,林柏泉,施天虎.贵州典型矿区突出煤孔隙结构及其吸附特性实验研究[J].采矿与安全工程学报,2013,30(3):415-420.LI Xijian,LIN Baiquan,SHI Tianhu. Experimental study on pore structures of outburst coal and its adsorption properties at typical mining fields in Guizhou province[J]. Journal of Mining and Safety Engineering,2013,30(3):415-420.
[4]张东明,白鑫,尹光志,等.低渗煤层液态CO2相变定向射孔致裂增透技术及应用[J].煤炭学报,2018,43(7):1938-1950.ZHANG Dongming,BAI Xin,YIN Guangzhi,et al. Research and application on technology of increased permeability by liquid CO2phase change directional jet fracturing in low-permeability coal seam[J]. Journal of China Coal Society,2018,43(7):1938-1950.
[5]岳立新,孙可明.超临界CO2作用时间对煤渗透率和孔隙率的影响规律研究[J].应用力学学报,2018,35(5):1170-1176,1194.YUE Lixin,SUN Keming. The influence law of action time by supercritical CO2on permeability and porosity of coal[J]. Chinese Journal of Applied Mechanics,2018,35(5):1170-1176,1194.
[6]林海飞,程博,李树刚,等.煤的吸附孔结构对瓦斯放散特性影响的实验研究[J].采矿与安全工程学报,2016,33(3):557-563.LIN Haifei,CHENG Bo,LI Shugang,et al. Experimental study on the effect of adsorption pore structure on gas emission characteristics[J]. Journal of Mining and Safety Engineering,2016,33(3):557-563.
[7]刘宝莉,严敏,林海飞,等.表面活性剂对煤体孔隙结构影响的实验研究[J].煤矿安全,2018,49(11):20-23,28.LIU Baoli,YAN Min,LIN Haife,et al. Experimental study on effect of surfactant on pore structure of coal[J]. Safety in Coal Mines,2018,49(11):20-23,28.
[8]许江,袁梅,李波波,等.煤的变质程度、孔隙特征与渗透率关系的试验研究[J].岩石力学与工程学报,2012,31(4):681-687.XU Jiang,YUAN Mei,LI Bobo,et al. Experimental study of relationships between metamorphic grade,pore characteristics and permeability of coal[J]. Chinese Journal of Rock Mechanics and Engineering,2012,31(4):681-687.
[9]高尚,王亮,高杰,等.基于分形理论的不同变质程度硬煤孔隙结构试验研究[J].煤炭科学技术,2018,46(8):93-100.GAO Shang,WANG Liang,GAO Jie,et al. Experimental study on pore structures of hard coal with different metamorphic grade based on fractal theory[J]. Coal Science and Technology,2018,46(8):93-100.
[10]傅雪海,秦勇,薛秀谦,等.煤储层孔、裂隙系统分形研究[J].中国矿业大学学报,2001,30(3):11-14.FU Xuehai,QIN Yong,XUE Xiuqian,et al. Fractal study on coal reservoir hole and fracture system[J]. Journal of China University of Mining&Technology,2001,30(3):11-14.
[11]刘顺喜,吴财芳.比德-三塘盆地煤储层不同尺度孔隙分形特征研究[J].煤炭科学技术,2016,44(2):33-38,67.LIU Shunxi,WU Caifang. Study on fractal characteristics of different scales pore coal reservoir in Bide-Santang Basin[J]. Coal Science and Technology,2016,44(2):33-38,67.
[12]陈科洛,张廷山,陈晓慧,等.页岩微观孔隙模型构建——以滇黔北地区志留系龙马溪组页岩为例[J].石油勘探与开发,2018,45(3):396-405.CHEN Keluo,ZHANG Tingshan,CHEN Xiaohui,et al. Model construction of micro-pores in shale:A case study of Silurian Longmaxi formation shale in Dianqianbei area,SW China[J]. Petroleum Exploration and Development,2018,45(3):396-405.
[13] BRUNAUER S,DEMING L S,DEMING W E,et al. On a theory of the van der Waals adsorption of gases[J]. Journal of the American Chemical Society,1940,62(7):1723-1732.
[14] SING K S W,EVERETT D H,HAUL R A W,et al. Reporting physisorption data gas/solid systems with special reference to the determination of surface area and porosity[J]. Pure and Applied Chemistry,1985,57(4):603-619.
[15]宋晓夏,唐跃刚,李伟,等.中梁山南矿构造煤吸附孔分形特征[J].煤炭学报,2013,38(1):134-139.SONG Xiaoxia,TANG Yuegang,LI Wei,et al. Fractal characteristics of adsorption pores of tectonic coal from Zhongliangshan southern coalmine[J]. Journal of China Coal Society,2013,38(1):134-139.
[16] PFEIFER P,WU Y J,COLE M W,et al. Multilayer adsorption on a fractally rough surface[J]. Physical Review Letters,1989,62(17):1997-2000.