Fractal Characteristics of Coal Rock Pores in the Baliancheng Mining Area, Hunchun Basin

doi:10.11885/j.issn.1674-5086.2018.10.10.03

Abstract

Abstract: Pore structure characteristics of coal rocks are important parameters for evaluating coal seam storage capacity and selecting fracturing layers. Low temperature nitrogen adsorption, nuclear magnetic resonance (NMR) technology, and argon ion polishing imaging enabled quantitative characterization of the pore heterogeneity by fractal theory were used to examine the influencing factors of fractal dimensions. The organic pores of the coal rocks from the Baliancheng mining area comprised mainly of plant tissue, intergranular, and gas pores, whereas the mineral pores were composed of dissolution and clay mineral pores. The type I curve indicated that the coal rock developed slit-like and wedge-shaped holes, while the type II curve indicated the development of bottle-shaped pores. The NMR bimodal T₂ spectrum showed that the adsorption pores were developed only to a limited degree with poor connectivity. The trimodality indicated the development of weep holes and fissures under good pore percolation conditions. When the pore diameter ranged between 2 and 100 nm, the water content and specific surface area were positively correlated with D₁, whereas D₂ was positively correlated with the ash content and negatively correlated with average pore size. When the pore diameter was between 0.1 and 10.0 μm, D_N1 obtained by NMR was positively correlated with the surface area of the pores and D_N2 was positively correlated with the volume of the percolation pores. In addition, D_M and the fractal dimension D_c of the dissolution pores were largely controlled by the clay mineral and feldspar contents, respectively. Therefore, coal layers exhibiting a nitrogen adsorption type I curve and trimodal nuclear magnetic T₂ map are conducive to the development of coalbed methane.

Key words: pore structure, fractal dimension, nitrogen adsorption, nuclear magnetic resonance, argon ion polishing, Hunchun Basin

CLC Number:

TE122

WANG Youzhi. Fractal Characteristics of Coal Rock Pores in the Baliancheng Mining Area, Hunchun Basin[J]. 西南石油大学学报(自然科学版), 2020, 42(1): 57-68.

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References

[1] 邹才能,杨智,朱如凯,等.中国非常规油气勘探开发与理论技术进展[J].地质学报,2015,89(6):979-1007. doi:10.3969/j.issn.0001-5717.2015.06.001 ZOU Caineng, YANG Zhi, ZHU Rukai, et al. Progress in China's unconventional oil & gas exploration and development and theoretical technologies[J]. Acta Geologica Sinica, 2015, 89(6):979-1007. doi:10.3969/j.issn.0001-5717.2015.06.001
[2] 朱如凯,邹才能,袁选俊,等.中国能源沉积学研究进展与发展战略思考[J].沉积学报,2017,35(5):1004-1015. doi:10.14027/j.cnki.cjxb.2017.05.012 ZHU Rukai, ZOU Caineng, YUAN Xuanjun, et al. Research progressand development strategic thinking on energy sedimentology[J]. Acta Sedimentologica Sinica, 2017, 35(5):1004-1015. doi:10.14027/j.cnki.cjxb.2017.05.012
[3] WANG Boyang, QIN Yong, SHEN Jian, et al. Pore structure characteristics of low and medium-rank coals and their differential adsorption and desorption effects[J]. Journal of Petroleum Science and Engineering, 2018, 165:1-12. doi:10.1016/j.petrol.2018.02.014
[4] NELSON P H. Pore-throat sizes in sandstones, tight sandstones, and shales[J]. AAPG Bulletin, 2009, 93(3):329-340. doi:10.1306/10240808059
[5] NIE Baisheng, LIU Xianfeng, YUAN Shaofei, et al. Sorption characteristics of methane among various rank coals:Impact of moisture[J]. Adsorption, 2016, 22(3):315-325. doi:10.1007/s10450-016-9778-9
[6] 张文静,琚宜文,卫明明,等.不同变质变形煤储层吸附/解吸特征及机理研究进展[J].地学前缘,2015,22(2):232-242. doi:10.13745/j.esf.2015.02.021 ZHANG Wenjing, JU Yiwen, WEI Mingming, et al. Study on characteristics and mechanism of adsorption/desorption on different metamorphic deformed coal reservoirs[J]. Earth Science Frontiers, 2015, 22(2):232-242. doi:10.13745/j.esf.2015.02.021
[7] 李国庆,孟召平,王保玉.高煤阶煤层气扩散一渗流机理及初期排采强度数值模拟[J].煤炭学报,2014,39(9):1919-1926. doi:10.13225/j.cnki.jccs.2014.8024 LI Guoqing, MENG Zhaoping, WANG Baoyu. Diffusion and seepage mechanisms of high rank coal-bed methane reservoir and its numerical simulation at early drainage rate[J]. Journal of China Coal Society, 2014, 39(9):1919-1926. doi:10.13225/j.cnki.jccs.2014.8024
[8] 张崇崇,王延斌,倪小明,等.煤层气直井排采过程中渗透率变化规律研究[J].中国矿业大学学报,2015,44(3):520-525. ZHANG Chongchong, WANG Yanbin, NI Xiaoming, et al. Research on permeability variation of coal reservoir in drainage process of CBM vertical wells[J]. Journal of China University of Mining & Technology, 2015, 44(3):520-525.
[9] 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. doi:10.13225/j.cnki.jccs.2015.0620 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. doi:10.13225/j.cnki.jccs.2015.0620
[10] 张岩,刘金城,徐浩,等.陆相与过渡相煤系页岩孔隙结构及分形特征对比——以鄂尔多斯盆地东北缘延安组与太原组为例[J].石油学报,2017,38(9):1036-1046. doi:10.7623/syxb201709005 ZHANG Yan, LIU Jincheng, XU Hao, et al. Comparison between pore structure and fractal characteristics of continental and transitional coal measures shale:A case study of Yan'an and Taiyuan Formations at the northeastern margin of Ordos Basin[J]. Acta Petrolei Sinica, 2017, 38(9):1036-1046. doi:10.7623/syxb201709005
[11] CAO Taotao, SONG Zhiguang, WANG Sibo, et al. Characterization of pore structure and fractal dimension of Paleozoic shales from the northeastern Sichuan Basin, China[J]. Journal of Natural Gas Science and Engineering, 2016, 35:882-895. doi:10.1016/j.jngse.2016.09.022
[12] TIAN Hui, PAN Lei, XIAO Xianming, et al. A preliminary study on the pore characterization of lower Silurian black shales in the Chuandong Thrust Fold Belt, southwestern China using low pressure N₂ adsorption and FE-SEM methods[J]. Marine and Petroleum Geology, 2013, 48:8-19. doi:10.1016/j.marpetgeo.2013.07.008
[13] LI Pengpeng, ZHANG Xiaodong, ZHANG Shuo. Structures and fractal characteristics of pores in low volatile bituminous deformed coals by low-temperature N₂ adsorption after different solventstreatments[J]. Fuel, 2018, 224:661-675. doi:10.1016/j.fuel.2018.03.067
[14] YAO Yanbin, LIU Dameng, TANG Dazhen, et al. Fractal characterization of adsorption-pores of coals from North China:An investigation on CH₄ adsorption capacity of coals[J]. International Journal of Coal Geology, 2008, 73(1):27-42. doi:10.1016/j.coal.2007.07.003
[15] 李凤丽,姜波,宋昱,等.低中煤阶构造煤的纳米级孔隙分形特征及瓦斯地质意义[J].天然气地球科学,2017,28(1):173-182. doi:10.11764/j.issn.1672-1926.2016.11.032 LI Fengli, JIANG Bo, SONG Yu, et al. Nano scale pore structure and fractal characteristics of low-medium metamorphic tectonically deformed coal[J]. Natural Gas Geoscience, 2017, 28(1):173-182. doi:10.11764/j.issn.1672-1926.2016.11.032
[16] YAO Yanbin, LIU Dameng, CHE Yao, et al. Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR)[J]. Fuel, 2010, 89(7):1371-1380. doi:10.1016/j.fuel.2009.11.005
[17] KROHN C E. Sandstone fractal and Euclidean pore volume distribution[J]. Journal of Geophys Research, Soild Earch, 1988, 93(B4):3286-3296. doi:10.1029/JB093iB04p03286
[18] HUANG S J, YU Y C, LEE T Y, et al. Correlations and characterization of porous solids by fractal dimension and porosity[J]. Physica A:Statistical Mechanics and its Applications, 1999, 274(3-4):419-432. doi:10.1016/s0378-4371(99)00299-x
[19] 徐祖新,张义杰,王居峰,等.渤海湾盆地沧东凹陷孔二段致密储层孔隙结构定量表征[J].天然气地球科学,2016,27(1):102-110. doi:10.11764/j.issn.1672-1926.2016.01.0102 XU Zuxin, ZHANG Yijie, WANG Jufeng, et al. Quantitative characterization of pore structure of the second member of Kongdian Formation tight reservoirs in Cangdong Sag[J]. Natural Gas Geoscience, 2016, 27(1):102-110. doi:10.11764/j.issn.1672-1926.2016.01.0102
[20] 高为,易同生,金军,等.黔西地区煤样孔隙综合分形特征及对孔渗性的影响田[J].煤炭学报,2017,42(5):1258-1265. doi:10.13225/j.cnki.jccs.2016.0869 GAO Wei, YI Tongsheng, JIN Jun, et al. Pore integrated fractal characteristic of coal sample in western Guizhou and its impact to porosity and permeability[J]. Journal of China Coal Society, 2017, 42(5):1258-1265. doi:10.13225/j.cnki.jccs.2016.0869
[21] 王有智.珲春盆地低煤阶煤层气富集规律[J].煤田地质与勘探,2015,43(3):28-32. doi:10.3969/j.issn.1001-1986.2015.03.006 WANG Youzhi. Low rank enrichment of coalbed methane in Hunchun Basin[J]. Coal Geology & Exploration, 2015, 43(3):28-32. doi:10.3969/j.issn.1001-1986.2015.03.006
[22] 张慧,李小彦,郝琦,等.中国煤的扫描电子显微镜研究[M].北京:地质出版社,2003:62-82. ZHANG Hui, LI Xiaoyan, HAO Qi, et al. Study on coal in China by scan electron microscope[M]. Beijing:Geological Publishing House, 2003:62-82.
[23] 张慧,王晓刚,员争荣,等.煤中显微裂隙的成因类型及其研究意义[J].岩石矿物学杂志,2002,21(3):278-274. doi:10.3969/j.issn.1000-6524.2002.03.010 ZHANG Hui, WANG Xiaogang, YUAN Zhengrong, et al. Genetic types of microfractures in coal and their significance[J]. Acta Petrologica Mineralogica, 2002, 21(3):278-274. doi:10.3969/j.issn.1000-6524.2002.03.010
[24] YANG Feng, NING Zhengfu, LIU Huiqing. Fractal characteristics of shales from a shale gas reservoir in the Sichuan Basin, China[J]. Fuel, 2014, 115:378-384. doi:10.1016/j.fuel.2013.07.040
[25] ZHOU Lei, KANG Zhihong. Fractal characterization of pores in shales using NMR:A casestudy from the Lower Cambrian Niutitang Formation in the middle Yangtze Platform, Southwest China[J]. Journal of Natural Gas Science and Engineering, 2016, 35:860-872. doi:10.1016/j.jngse.2016.09.030
[26] ZHOU Sandong, LIU Dameng. Fractal characterization of pore-fracture in low-rank coals using a low-field NMR relaxation method[J]. Fuel, 2016, 181:218-226. doi:10.1016/j.fuel.2016.04.119
[27] YAO Yanbin, LIU Dameng. Comparison of low-field NMR and mercury intrusion porosimetry in characterizing pore size distributions of coal[J]. Fuel, 2012, 95:152-158. doi:10.1016/j.fuel.2011.12.039
[28] YANG Rui, HE Sheng, YI Jizheng, et al. Nano-scale pore structure and fractal dimensionof organic-rich Wufeng-Longmaxi shale from Jiaoshiba Area, Sichuan Basin:Investigations using FE-SEM, gas adsorption and helium pycnometry[J]. Marine and Petroleum Geology, 2016, 70:27-45. doi:10.1016/j.marpetgeo.2015.11.019
[29] LI Ang, DING Wenlong, JIU Kai, et al. Investigation of the pore structures and fractal characteristics of marineshale reservoirs using NMR experiments and image analyses:A case study of the Lower Cambrian Niutitang Formation in northern Guizhou province, South China[J]. Marine and Petroleum Geology, 2016, 89:46-57. doi:10.1016/j.marpetgeo.2017.10.019