煤孔隙结构对瓦斯解吸−扩散−渗流过程的影响

贾男

doi:10.13272/j.issn.1671-251x.2023110076

煤孔隙结构对瓦斯解吸−扩散−渗流过程的影响

doi: 10.13272/j.issn.1671-251x.2023110076

贾男^{1, 2,}

1.
中煤科工集团沈阳研究院有限公司，辽宁抚顺　113122
2.
煤矿安全技术国家重点实验室，辽宁抚顺　113122

基金项目: 辽宁省科技计划联合基金项目（2023JH2/101700008）。

详细信息

作者简介:
贾男（1989—），男，锡伯族，辽宁沈阳人，副研究员，硕士，主要研究方向为煤矿瓦斯治理，E-mail：jn_1989@163.com

中图分类号: TD712
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- 被引次数: 0
出版历程
- 收稿日期: 2023-11-23
- 修回日期: 2024-03-18
- 网络出版日期: 2024-04-11

The influence of coal pore structure on gas desorption-diffusion-seepage process

JIA Nan^{1, 2
,}

1.
CCTEG Shengyang Research Insititute, Fushun 113122, China
2.
State Key Laboratory of Coal Mine Safety Technology, Fushun 113122, China

摘要

摘要: 充分认识煤层瓦斯运移机制是提升抽采效率的根本前提。而目前针对煤体瓦斯微观运移特性的研究探讨的多是煤微观孔隙瓦斯运移特性，忽略了瓦斯解吸−扩散过程。以焦煤为例，采用压汞测试、纳米级工业CT扫描和数值仿真，精准重构并定量表征了煤孔隙空间结构，从微观角度分析了瓦斯解吸−扩散−渗流的演化过程，初步探讨了煤孔隙空间结构对瓦斯运移的影响。结果表明：① 在孔隙中心位置的瓦斯压力相对较高，解吸−扩散由孔隙中心向边缘进行，不同时间及位置上瓦斯压力分布规律差异明显，造成瓦斯压力分布差异性的原因在于各代表性体积（REV）单元中孔隙与喉道的半径、长度、形状、连通性能不同。② 孔隙结构和拓扑优势拓展了瓦斯解吸−扩散−渗流范围，大尺寸孔隙结构能为气体分子提供多元化运动空间，削弱尺寸效应对扩散广度的影响，促进瓦斯解吸−扩散速率。③ 强非均质连通孔隙结构中，瓦斯渗流分散而高效，能通过广泛沟通煤基质完成气体由扩散到渗流的转变，提升瓦斯传质效率；弱非均质连通孔隙结构中，气体渗流路径单一、流线集中，渗流传质阻力较大，气体分子由扩散到渗流的转变效率低，不利于瓦斯高效运移。研究结果从微观角度丰富了煤体瓦斯运移理论，为瓦斯抽采工程实践提供了理论基础。
- 瓦斯抽采 /
- 煤层瓦斯 /
- 孔隙结构 /
- 瓦斯解吸 /
- 瓦斯扩散 /
- 瓦斯渗流 /
- CT扫描
Abstract: Fully understanding the mechanism of coal seam gas migration is the fundamental prerequisite for improving extraction efficiency. At present, research on the micro migration features of coal gas mostly focuses on the micro pore gas migration features of coal, ignoring the gas desorption-diffusion process. Taking coking coal as an example, the pore space structure of coal is accurately reconstructed and quantitatively characterized using mercury intrusion testing, nanoscale industrial CT scanning, and numerical simulation. The evolution process of gas desorption-diffusion-seepage is analyzed from a microscopic perspective, and the influence of coal pore space structure on gas migration is preliminarily explored. The results show the following points. ① The gas pressure is relatively high at the center of the pore, and desorption-diffusion proceeds from the center of the pore to the edge. The distribution of gas pressure varies significantly at different times and positions. The reason for the difference in gas pressure distribution is that the radius, length, shape, and connectivity of pores and throats in each representative elementary volume (REV) unit are different. ② The pore structure and topological advantages expand the range of gas desorption-diffusion-seepage. The large-sized pore structure can provide diversified movement space for gas molecules, weaken the influence of size effect on diffusion breadth, and promote the rate of gas desorption-diffusion. ③ In the strongly heterogeneous connected pore structure, gas seepage is dispersed and efficient, and the transformation of gas from diffusion to seepage can be achieved through extensive communication with the coal matrix, improving the efficiency of gas mass transfer. In weakly heterogeneous connected pore structures, the gas seepage path is single, the seepage lines are concentrated, the mass transfer resistance of the seepage is high, and the transformation efficiency of gas molecules from diffusion to seepage is low. It is not conducive to efficient gas migration. The research results enrich the theory of coal gas migration from a microscopic perspective and provide a theoretical basis for gas extraction engineering practice.
- gas extraction /
- coal seam gas /
- pore structure /
- gas desorption /
- gas diffusion /
- gas seepage /
- CT scan

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图 1 实验样品

Figure 1. Experimental samples

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图 2 实验仪器

Figure 2. Experimental instruments

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图 3 降噪前后CT图像对比

Figure 3. CT image comparison before and after noise reduction

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图 4 孔隙灰度阈值的Bi−PTI拟合结果

Figure 4. Bi-PTI fitting resules of pore gray threshold

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图 5 瓦斯边界条件

Figure 5. Gas boundary condition

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图 6 数字岩心重构结果

Figure 6. Digital core reconstruction results

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图 7 REV表征单元孔隙空间结构

Figure 7. Representative elementary volume(REV) characterisation of unit pore space structure

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图 8 孔隙等效直径分布规律

Figure 8. Distribution law of pore equivalent diameter

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图 9 孔隙体积分布规律

Figure 9. Distribution law of pore volume

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图 10 瓦斯压力空间分布

Figure 10. Space distribution of gas pressure

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图 11 REV单元y−z截面孔隙压力分布

Figure 11. Pore pressure distribution in y-z section of REV unit

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图 12 瓦斯渗流速度流线分布

Figure 12. Velocity streamline distribution of gas seepage

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表 1 Bi−PTI模型拟合参数

Table 1. Fitting parameters of Bi-PTI model

煤样	γ₁/ 10⁴ HU	γ₂/ 10⁴ HU	ζ₁/10⁻⁴	ζ₂/10⁻⁴	$\omega $	相关系数	G_m/HU
5号煤	5.32	3.81	3.110	0.94	0.44	0.99	10475
6号煤	1.31	2.45	2.100	0.81	0.65	0.99	12923

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表 2 数值模拟参数

Table 2. Numerical simulation parameters

参数	5号煤	6号煤
R/（J·K⁻¹·mol⁻¹）	8.314	8.314
T/K	303	303
s/m²	5.6×10⁻⁹	5.9×10⁻⁹
a/（m³·kg⁻¹）	0.0112	0.0112
b/MPa⁻¹	1.86×10⁻⁷	1.86×10⁻⁷
V_m/（m³·kg⁻¹）	0.024	0.024
f/m²	1×10⁻⁹	1.2×10⁻⁹
N_solid	2.2×10¹⁷	2.1×10¹⁷
V_voxel/m³	1×10⁻¹⁸	1×10⁻¹⁸
ρ/（kg·m⁻³）	1260	1260
V_e/m³	3.1×10⁻¹⁴	3.0×10⁻¹⁴
D/（m²·s⁻¹）	3.60×10⁻¹²	3.60×10⁻¹²
P/MPa	1.0×10⁻²	1.0×10⁻²

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参考文献(20)

[1]	王恩元,张国锐,张超林,等. 我国煤与瓦斯突出防治理论技术研究进展与展望[J]. 煤炭学报,2022,47(1):297-322. WANG Enyuan,ZHANG Guorui,ZHANG Chaolin,et al. Research progress and prospect on theory and technology for coal and gas outburst control and protection in China[J]. Journal of China Coal Society,2022,47(1):297-322.
[2]	于国卿,翟成,秦雷,等. 超声波功率对煤体孔隙影响规律研究[J]. 中国矿业大学学报,2018,47(2):264-270,322. YU Guoqing,ZHAI Cheng,QIN Lei,et al. Changes to coal pores by ultrasonic wave excitation of different powers[J]. Journal of China University of Mining & Technology,2018,47(2):264-270,322.
[3]	王登科,张航,魏建平,等. 基于工业CT扫描的瓦斯压力影响下含瓦斯煤裂隙动态演化特征[J]. 煤炭学报,2021,46(11):3550-3564. WANG Dengke,ZHANG Hang,WEI Jianping,et al. Dynamic evolution characteristics of fractures in gas-bearing coal under the influence of gas pressure using industrial CT scanning technology[J]. Journal of China Coal Society,2021,46(11):3550-3564.
[4]	王耀锋,何学秋,王恩元,等. 水力化煤层增透技术研究进展及发展趋势[J]. 煤炭学报,2014,39(10):1945-1955. WANG Yaofeng,HE Xueqiu,WANG Enyuan,et al. Research progress and development tendency of the hydraulic technology for increasing the permeability of coal seams[J]. Journal of China Coal Society,2014,39(10):1945-1955.
[5]	刘学锋. 基于数字岩心的岩石声电特性微观数值模拟研究[D]. 青岛:中国石油大学(华东),2010. LIU Xuefeng. Numerical simulation of elastic and electrical properties of rock based on digital cores[D]. Qingdao:China University of Petroleum(East China),2010.
[6]	崔冠哲,申林方,王志良,等. 基于格子Boltzmann方法土体CT扫描切片细观渗流场的数值模拟[J]. 岩土力学,2016,37(5):1497-1502. CUI Guanzhe,SHEN Linfang,WANG Zhiliang,et al. Numerical simulation of mesoscopic seepage field of soil CT scanned slice based on lattice Boltzmann method[J]. Rock and Soil Mechanics,2016,37(5):1497-1502.
[7]	王刚,秦相杰,江成浩,等. 温度作用下CT三维重建煤体微观结构的渗流和变形模拟[J]. 岩土力学,2020,41(5):1750-1760. WANG Gang,QIN Xiangjie,JIANG Chenghao,et al. Simulations of temperature effects on seepage and deformation of coal microstructure in 3D CT reconstructions[J]. Rock and Soil Mechanics,2020,41(5):1750-1760.
[8]	白若男. 压力条件对煤体微观孔隙模型水渗流的影响[J]. 煤矿安全,2016,47(12):180-183. BAI Ruonan. Influence of stress conditions on water seepage of coal microscopic pore model[J]. Safety in Coal Mines,2016,47(12):180-183.
[9]	JU Yang,WANG Yongliang,DONG Hongyu,et al. Numerical analysis of the hydrofracturing behaviour of heterogeneous glutenite considering hydro-mechanical coupling effects based on bonded particle models[J]. International Journal for Numerical and Analytical Methods in Geomechanics,2018,42(13):1493-1515. doi: 10.1002/nag.2801
[10]	JU Yang,XI Chaodong,ZHANG Yang,et al. Laboratory in situ CT observation of the evolution of 3D fracture networks in coal subjected to confining pressures and axial compressive loads:a novel approach[J]. Rock Mechanics and Rock Engineering,2018,51(11):3361-3375. doi: 10.1007/s00603-018-1459-4
[11]	李兆霖,王连国,姜崇扬,等. 基于实时CT扫描的岩石真三轴条件下三维破裂演化规律[J]. 煤炭学报,2021,46(3):937-949. LI Zhaolin,WANG Lianguo,JIANG Chongyang,et al. Three-dimensional fracture evolution patterns of rocks under true triaxial conditions based on real-time CT scanning[J]. Journal of China Coal Society,2021,46(3):937-949.
[12]	方辉煌. 基于数字岩石物理技术的无烟煤储层CO₂−ECBM流体连续过程数值模拟研究[D]. 徐州:中国矿业大学,2020. FANG Huihuang. Numerical simulation of the CO₂-ECBM fluid continuous process in anthracite reservoirs based on digital petrophysical technology[D]. Xuzhou:China University of Mining and Technology,2020.
[13]	黄笑乐,杨甫,韩磊,等. 富油煤(长焰煤)孔隙结构三维表征及渗流模拟[J]. 化工学报,2022,73(11):5078-5087. HUANG Xiaole,YANG Fu,HAN Lei,et al. 3D characterization of pore structure and seepage simulation of tar-rich coal(long flame coal)[J]. CIESC Journal,2022,73(11):5078-5087.
[14]	姜基露. 基于深度学习的岩石薄片图像岩性识别研究[D]. 大庆:东北石油大学,2023. JIANG Jilu. Research on lithology recognition of rock slice image based on deep learning[D]. Daqing:Northeast Petroleum University,2023.
[15]	宋党育,何凯凯,吉小峰,等. 基于CT扫描的煤中孔裂隙精细表征[J]. 天然气工业,2018,38(3):41-49. doi: 10.3787/j.issn.1000-0976.2018.03.005 SONG Dangyu,HE Kaikai,JI Xiaofeng,et al. Fine characterization of pores and fractures in coal based on a CT scan[J]. Natural Gas Industry,2018,38(3):41-49. doi: 10.3787/j.issn.1000-0976.2018.03.005
[16]	郝晨光,郭晓阳,邓存宝,等. 基于Bi−PTI模型的CT数字煤岩孔裂隙精准识别及阈值反演[J]. 煤炭学报,2023,48(4):1516-1526. HAO Chenguang,GUO Xiaoyang,DENG Cunbao,et al. Precise identification and threshold inversion of pores and fissures in CT digital coal rock based on Bi-PTI model[J]. Journal of China Coal Society,2023,48(4):1516-1526.
[17]	宋晓夏,唐跃刚,李伟,等. 基于显微CT的构造煤渗流孔精细表征[J]. 煤炭学报,2013,38(3):435-440. SONG Xiaoxia,TANG Yuegang,LI Wei,et al. Advanced characterization of seepage pores in deformed coals based on micro-CT[J]. Journal of China Coal Society,2013,38(3):435-440.
[18]	车禹恒. 鄂尔多斯盆地低阶煤渗流孔隙拓扑结构非均质特征研究[J]. 煤矿安全,2021,52(8):33-38. CHE Yuheng. Study on heterogeneous characteristics of topology structure of low-rank coal seepage pores in Ordos Basin[J]. Safety in Coal Mines,2021,52(8):33-38.
[19]	章飞,张攀. 鄂尔多斯盆地低阶煤孔隙瓦斯微观渗流特征[J]. 煤矿安全,2020,51(8):17-22,27. ZHANG Fei,ZHANG Pan. Characteristics of methane micro-seepage in low-rank coal pores of Ordos Basin[J]. Safety in Coal Mines,2020,51(8):17-22,27.
[20]	WANG Xianglong,PAN Jienan,WANG Kai,et al. Characterizing the shape,size,and distribution heterogeneity of pore-fractures in high rank coal based on X-ray CT image analysis and mercury intrusion porosimetry[J]. Fuel,2020,282. DOI: 10.1016/j.fuel.2020.118754.