鄂尔多斯盆地本溪组煤岩微观特征及气体赋存状态

doi:10.7657/XJPG20250301

摘要/Abstract

摘要：

鄂尔多斯盆地上石炭统本溪组煤岩气勘探开发处于初期阶段，有关煤岩微观组成、孔隙结构及其对气体赋存状态的控制作用的认识程度较低。利用显微观察、X射线衍射、微米CT扫描、低温CO₂吸附、低温N₂吸附、高压压汞、高压釜-黄金管热模拟等技术，分析了本溪组8号煤层煤岩的显微组分含量、工业组分含量、孔隙结构特征及气体赋存状态。结果表明：研究区8号煤层以光亮煤和半亮煤为主，镜质组平均含量为78.8%，惰质组平均含量为18.2%，壳质组平均含量为1.0%；煤岩固定碳平均含量为70.00%，灰分平均含量为13.90%，属于低灰分煤；微孔、介孔和宏孔对煤岩总孔隙体积贡献率分别为75.7%、14.4%和9.9%，比表面积占比分别为98.3%、1.0%和0.7%，微孔对煤岩总孔隙体积和比表面积的贡献率均最大；煤岩吸附气和游离气占比分别为74.7%和25.3%，吸附气含量与微孔孔体积及微孔比表面积呈正相关关系，游离气含量与宏孔孔体积呈近似正相关关系。

关键词: 鄂尔多斯盆地, 石炭系, 本溪组, 煤岩, 微观特征, 孔隙结构, 气体赋存状态

Abstract:

Coal rock gas (CRG) in the Upper Carboniferous Benxi formation in the Ordos Basin is currently in the early stage of exploration and development, and knowledge regarding the coal rock’s microscopic composition, pore structure, and their controls on gas occurrence remains limited. By using techniques including petrographic microscopy, X-ray diffraction (XRD), micro-CT scanning, low-temperature CO₂ adsorption, low-temperature N₂ adsorption, high-pressure mercury intrusion, and high-pressure autoclave-gold tube pyrolysis simulation, etc., the maceral composition, industrial component, pore structure, and gas occurrence states in the No. 8 coal seam of the Benxi formation in the study area were investigated. The results show that the No. 8 coal seam is dominated by bright and semi-bright coals, with average vitrinite, inertinite, and exinite contents of 78.8%, 18.2%, and 1.0%, respectively. The coal rock exhibits an average fixed carbon content of 70.00% and an ash content of 13.90%, indicative of low-ash coal. The micropores, mesopores, and macropores contribute 75.7%, 14.4%, and 9.9% to the total pore volume, respectively, while their specific surface area proportions are 98.3%, 1.0%, and 0.7%, respectively. The micropores contribute the most to both total pore volume and specific surface area. The adsorbed gas and free gas account for 74.7% and 25.3% of the total gas content, respectively. The adsorbed gas content is positively correlated with micropore volume and micropore specific surface area, while the free gas content shows an approximately positive correlation with macropore volume.

Key words: Ordos Basin, Carboniferous, Benxi formation, coal rock, microscopic characteristic, pore structure, gas occurrence

中图分类号:

TE122

黄有根, 郑小鹏, 张道锋, 胡薇薇, 何梦卿, 王冰. 鄂尔多斯盆地本溪组煤岩微观特征及气体赋存状态[J]. 新疆石油地质, 2025, 46(3): 253-262.

HUANG Yougen, ZHENG Xiaopeng, ZHANG Daofeng, HU Weiwei, HE Mengqing, WANG Bing. Microscopic Characteristics of and Gas Occurrence in Coal Rock in Benxi Formation, Ordos Basin[J]. Xinjiang Petroleum Geology, 2025, 46(3): 253-262.

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井名	深度/m	低温CO₂吸附		低温N₂吸附		高压压汞
井名	深度/m	孔体积/ （cm³·g^-1）	比表面积/ （m²·g^-1）	孔体积/ （cm³·g^-1）	比表面积/ （m²·g^-1）	孔体积/ （cm³·g^-1）	比表面积/ （m²·g^-1）
A32井	3 400.8	0.041 0	135.52	0.002 2	1.08	0.005 4	0.93
A36井	2 804.6	0.062 2	199.40	0.003 0	1.11	0.004 8	0.84
A36井	2 805.6	0.063 2	206.71	0.004 1	0.81	0.003 5	0.97
A36井	2 809.9	0.053 3	172.11	0.004 1	1.00	0.003 9	0.99
A55井	2 178.8	0.029 4	89.22	0.013 0	2.32	0.005 7	1.32
A78井	2 353.2	0.031 7	96.03	0.006 3	1.01	0.005 1	0.84
A78井	2 354.4	0.049 5	150.61	0.005 2	0.64	0.007 1	1.38
A88井	2 505.1	0.068 2	239.60	0.007 2	2.21	0.007 1	1.46
G11井	3 258.1	0.011 7	36.14	0.006 0	1.10	0.005 6	1.22
G11井	3 261.7	0.023 1	72.73	0.030 4	2.52	0.006 4	1.13

镜质体反射率/%	总有机碳产气率/（mg·g^-1）	面孔率/%		不同孔隙占比/%
镜质体反射率/%	总有机碳产气率/（mg·g^-1）	有机孔	无机孔	微孔	介孔	宏孔
0.55	2.1	0.9	2.3	20.3	32.4	47.3
0.85	4.3	1.5	2.7	17.9	31.2	50.9
1.02	8.6	2.0	3.0	22.1	32.5	45.4
1.41	19.4	3.2	2.8	33.2	29.8	37.0
1.59	26.4	3.6	2.4	45.5	29.2	25.3
1.90	42.9	4.0	1.9	57.1	27.1	15.8
2.14	54.4	4.3	1.4	75.9	18.5	5.6
3.52	102.4	3.9	0.4	78.6	6.2	15.2