鄂尔多斯盆地东部深部煤系储层微观孔隙结构特征及启示

doi:10.13809/j.cnki.cn32-1825/te.2025.02.006

摘要/Abstract

摘要：

鄂尔多斯盆地东部深部煤层气资源丰富，实现煤系气综合开发有助于提高资源动用率和单井产气量。为精准确定“甜点”层，利用有机地化、双束扫描电镜、高压压汞、低温N₂吸附和低温CO₂吸附等试验，对鄂尔多斯盆地东部山西组山2段煤系泥岩、煤岩和致密砂岩孔隙发育特征进行对比。结果表明黏土矿物含量是影响煤系地层泥岩和致密砂岩孔隙发育的主要影响因素。煤系储层微观孔隙结构差异较大，泥岩和致密砂岩主要发育介孔（2 ~ 50 nm）尺度的黏土矿物孔隙，二者的介孔比表面积和孔体积大致相等；煤岩发育大量微孔尺度（<2 nm）的有机质纳米孔隙，微孔比表面积远大于泥岩和致密砂岩的介孔比表面积；致密砂岩同时发育大量宏孔（>50 nm）尺度的黏土矿物孔隙和微裂缝，其连通性好于泥岩。致密砂岩能为游离气提供大量储集空间，泥岩和煤岩孔隙可以吸附大量天然气，砂泥煤组合和砂煤组合是煤系地层的主要勘探目标。

关键词: 深部煤系气, 孔隙结构, 储层特征, 孔隙差异, 鄂尔多斯盆地

Abstract:

The deep coalbed methane resources in the eastern Ordos Basin are abundant, and comprehensive development of coal measure gas can enhance resource utilization and improve single well gas production. To precisely identify the “sweet spot layer,” this study compares the pore development characteristics of coal measure mudstone, coal rock and tight sandstone in the Shan 2 Section of the Shanxi Formation in the eastern Ordos Basin using organic geochemical analysis, dual-beam scanning electron microscopy, high-pressure mercury intrusion, low-temperature N₂ adsorption, and low-temperature CO₂ adsorption tests. The results show that clay mineral content is the main factor influencing pore development in coal measure mudstone and tight sandstone. The microscopic pore structure of coal measure reservoirs exhibits significant variations: mudstones and tight sandstones are characterized by mesopores (2-50 nm) within clay minerals, with their mesopore-specific surface area and pore volume being roughly equal. Coal develops abundant micropores (<2 nm) in organic nanopores, with a micropore-specific surface area far exceeding the mesopore-specific surface area of mudstone and tight sandstone. Tight sandstone also develops numerous macropores (>50 nm) in clay mineral pores and microfractures, exhibiting better connectivity than mudstone. Tight sandstone provides substantial storage space for free gas, while the pores in mudstone and coal can adsorb a large amount of natural gas. The sand-mud-coal and sand-coal combinations are the main exploration targets for coal measure strata.

Key words: deep coal measure gas, pore structure, reservoir characteristics, pore differences, Ordos Basin

中图分类号:

TE135

马立涛,吴鹏,杨江浩, 等. 鄂尔多斯盆地东部深部煤系储层微观孔隙结构特征及启示[J]. 油气藏评价与开发, 2025, 15(2): 217-226.

MA Litao,WU Peng,YANG Jianghao, et al. Microscopic pore structure characteristics and implications of deep coal measure reservoirs in eastern Ordos Basin[J]. Petroleum Reservoir Evaluation and Development, 2025, 15(2): 217-226.

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样品编号	深度/m	亚段	岩性	ω（TOC）/%	R_o/%	含气量/（m³/t）
M5-1	1 919.35	山2¹	深灰色粉砂质泥岩	0.54	1.37	0.19
M5-2	1 920.25	山2¹	黑色炭质泥岩	1.91	1.36	0.35
M5-3	1 923.06	山2¹	煤	77.30		6.52
M5-4	1 927.42	山2¹	灰色中粒岩屑砂岩		1.25	0.09
M5-5	1 930.63	山2²	煤	81.60	1.39	6.31
M5-6	1 935.27	山2²	黑色泥质粗粉砂岩			0.40
M5-7	1 938.56	山2²	深灰色细粒岩屑砂岩			0.50
M5-8	1 939.29	山2²	灰色中粒岩屑砂岩			0.47
M5-9	1 939.92	山2²	灰色细粒岩屑砂岩			0.35
M5-10	1 941.33	山2²	灰色粗粒岩屑砂岩			0.20
M5-11	1 942.56	山2³	煤	76.70	1.47	6.96
M5-12	1 947.26	山2³	黑色细粒岩屑砂岩			0.18
M5-13	1 947.76	山2³	灰黑色含粗粉砂泥岩	2.53	1.47	0.07
M5-14	1 948.21	山2³	灰色含粗粉砂泥岩	1.80	1.39	0.14
M5-15	1 949.35	山2³	灰色细粒岩屑砂岩	0.59	1.36	0.26
M5-16	1 949.86	山2³	灰色细粒岩屑砂岩	7.18	1.40	0.30
M5-17	1 950.25	山2³	灰色粗粒岩屑砂岩	2.37	1.39	0.27
M5-18	1 950.72	山2³	灰色中粒岩屑砂岩	6.12	1.44	0.08
M5-19	1 951.10	山2³	灰色中粒岩屑砂岩	11.10	1.37	0.16
M5-20	1 951.62	山2³	灰色不等粒岩屑砂岩	8.58	1.40	0.31

样品编号	单元划分	BET比表面积/(m²/g)	BJH孔体积/(cm³/g)	平均孔直径/nm
M5-1	山2¹	10.40	0.023 2	9.96
M5-2	山2¹	4.30	0.015 9	14.55
M5-3	山2¹	0.63	0.002 8	22.11
M5-4	山2¹	9.12	0.026 9	11.99
M5-5	山2²	0.81	0.003 4	18.65
M5-6	山2²	6.28	0.018 6	12.31
M5-7	山2²	4.77	0.016 0	13.07
M5-8	山2²	4.43	0.014 4	12.79
M5-9	山2²	3.28	0.012 6	14.36
M5-10	山2²	2.30	0.012 2	18.81
M5-11	山2³	0.71	0.003 3	22.04
M5-12	山2³	4.40	0.015 2	14.25
M5-13	山2³	4.25	0.013 4	13.96
M5-14	山2³	5.64	0.017 4	12.83
M5-15	山2³	5.69	0.018 3	12.96
M5-16	山2³	2.05	0.009 9	17.18
M5-17	山2³	3.88	0.015 4	15.12
M5-18	山2³	8.62	0.026 4	12.09
M5-19	山2³	7.68	0.023 8	12.50
M5-20	山2³	2.90	0.014 7	17.17