黔西煤储层孔隙结构特征与储气性研究:以戴家田煤矿D1井为例

doi:10.19657/j.geoscience.1000-8527.2023.091

摘要/Abstract

摘要：

煤储层的微观孔隙是烃类气体赋存的主要位置,其微观孔隙结构特征对储气能力具有重要影响。研究煤储层孔隙及储气性对煤层气开采层段选取和瓦斯治理保护层选择具有基础性意义。黔西地区煤炭及煤层气资源丰富,但尚未见对煤储层孔隙结构特征及储气性研究。基于此,本文选取黔西织纳煤田戴家田矿D1井的二叠系龙潭组煤岩样品为研究对象,综合运用场发射扫描电镜、高压压汞、低温N₂吸附及高温等温吸附等实验手段,对各煤层孔隙结构特征进行分析,并探讨煤储层孔隙结构特征对储气性的影响。结果表明研究区龙潭组煤储层微观孔隙类型多样,微孔、小孔、中孔和大孔均有发育,且不同煤样孔隙的种类、形态和成因类型存在差异,微孔的比表面积与CH₄最大吸附气量和现场解吸气量均呈现一定的正相关性,对CH₄吸附能力起到决定性作用。此次研究发现研究区14煤和27煤储气性较好,资源潜力较大,可考虑作为煤层气地面开采优质层段。

关键词: 黔西地区, 龙潭组, 煤层气, 孔隙结构, 储气性

Abstract:

Microscopic pores in coal reservoirs are the primary space for hydrocarbon gas occurrence, thus the structural characteristics of these pores significantly influence gas storage capacity. Understanding these pores and the gas storage properties of coal reservoirs is of great crucial for determining coalbed methane extraction intervals and gas control protection layers. The Western Guizhou region is rich in coal and coalbed methane resources, however, there is limited research on the pore structure characteristics and gas storage properties of its coal reservoirs. This paper uses coal samples from the Permian Longtan Formation, located in Well D1 of the Daijiatian Mine in the Zhina Coalfield, as a case study. The pore structure characteristics of coal reservoirs in the research area were analyzed using field emission scanning electron microscopy, high-pressure mercury method, low temperature N₂ adsorption, and high-temperature isothermal adsorption methods. Moreover, the influence of pore structure characteristics on gas storage was discussed. The results indicate that the Longtan Formation coal reservoirs contain a diverse range of micropores, including well-developed micropores, small pores, medium pores, and large pores. The types, forms, and origins of these pores vary among different coals. The specific surface area of micropores is positively correlated with the maximum adsorption volume and on-site desorption volume of CH₄, which plays a key role in the adsorption capacity of CH₄. This study identified that 14 coal and 27 coal areas have strong gas storage potential and large resource potential, making them suitable as high-quality layers for surface mining of coalbed methane.

Key words: Western Guizhou, Longtan Formation, coalbed methane, pore structure, gas storage

中图分类号:

包庆林, 邓恩德, 马子杰, 姜秉仁. 黔西煤储层孔隙结构特征与储气性研究:以戴家田煤矿D1井为例[J]. 现代地质, 2024, 38(06): 1532-1544.

BAO Qinglin, DENG Ende, MA Zijie, JIANG Bingren. Research on the Pore Structure Characteristics and Gas Storage Properties of Coal Reservoirs in Western Guizhou: A Case Study of Well D1 in Daijiatian Coal Mine[J]. Geoscience, 2024, 38(06): 1532-1544.

图/表 18

图1 黔西戴家田煤矿大地构造图(a)、地质背景图(b)及综合地层柱状剖面图(c)

Fig.1 Geological background map (a), construction map (b), and composite stratigraphic column (c) of the Daijiatian Coal Mine in Western Guizhou

表1 黔西戴家田煤矿煤样基础参数

Table 1 Basic parameters of coal samples from the Daijiatian Coal Mine in Western Guizhou

编号	深度(m)	水分(M_ad)(%)	灰分(A_ad)(%)	挥发分(V_daf)(%)	镜质组(%)	惰质组(%)	有机组分总量(%)	R_o(%)
6煤	425.00	2.56	27.57	10.22	55.8	21.7	77.5	2.85
14煤	475.71	2.48	17.24	9.12	64.3	24.7	89.0	3.09
16煤	506.13	1.69	18.99	15.57	56.2	20.7	76.9	3.06
27煤	580.00	2.80	22.49	7.32	71.2	22.3	93.5	3.15
32煤	612.80	2.80	38.32	11.11	58.4	21.5	79.9	3.17

表2 黔西戴家田煤矿龙潭组煤储层孔隙类型

Table 2 Pore types in the coal reservoir of the Longtan Formation from the Daijiatian Coal Mine in Western Guizhou

编号	孔隙类型
6煤	气孔、角砾孔、碎粒孔、摩擦孔
14煤	气孔、角砾孔、碎粒孔
16煤	胞间孔、屑间孔、气孔
27煤	气孔、角砾孔、碎粒孔、晶间孔
32煤	气孔、屑间孔、铸模孔

图2 黔西戴家田煤矿龙潭组煤储层孔隙镜下特征 (a)胞腔孔,16煤,506.13 m;(b)屑间孔,16煤,506.13 m;(c)气孔,6煤,425.00 m;(d)角砾孔,14煤,475.71 m;(e)碎粒孔,27煤,580.00 m;(f)摩擦孔,6煤,425.00 m; (g)(h)铸模孔,32煤,612.80 m,图(h)为图(g)局部放大;(i)晶间孔,32煤,612.80 m

Fig.2 Microscopic pore characteristics of coal reservoirs in the Longtan Formation from the Daijiatian Coal Mine in Western Guizhou

图3 黔西戴家田煤矿龙潭组煤储层进汞退汞曲线(1 psi=6.895 kPa)

Fig.3 Diagrams of mercury intrusion and ejection in the Longtan Formation coal reservoir from the Daijiatian Coal Mine in Western Guizhou

表3 黔西戴家田煤矿基于压汞数据的龙潭组煤储层孔体积分布

Table 3 Pore volume distribution for the Longtan Formation coal reservoir, based on mercury injection data from the Daijiatian Coal Mine in Western Guizhou

编号	总孔体积 (cm³·g^-1)	阶段孔容(cm³·g^-1)				阶段孔容比例(%)
编号	总孔体积 (cm³·g^-1)	微孔	小孔	中孔	大孔	微孔	小孔	中孔	大孔
6煤	0.0308	0.0069	0.0118	0.0075	0.0046	22.40	38.31	24.35	14.94
14煤	0.0232	0.0080	0.0111	0.0024	0.0017	34.48	47.84	10.34	7.33
16煤	0.0296	0.0070	0.0206	0.0014	0.0006	23.65	69.59	4.73	2.03
27煤	0.0250	0.0084	0.0134	0.0016	0.0016	33.60	53.60	6.40	6.40
32煤	0.0271	0.0073	0.0119	0.0027	0.0052	26.94	43.91	9.96	19.19

表4 黔西戴家田煤矿基于压汞数据的龙潭组煤储层比表面积分布

Table 4 Specific surface area distribution for the Longtan Formation coal reservoir, based on mercury injection data from the Daijiatian Coal Mine in Western Guizhou

编号	比表面积 (m²·g^-1)	阶段比表面积(m²·g^-1)				阶段比表面积比例(%)
编号	比表面积 (m²·g^-1)	微孔	小孔	中孔	大孔	微孔	小孔	中孔	大孔
6煤	5.99800	3.45100	2.44350	0.09869	0.00481	57.54	40.74	1.65	0.08
14煤	6.20400	3.86100	2.30767	0.03321	0.00212	62.23	37.20	0.54	0.03
16煤	6.87400	2.93700	3.91553	0.02017	0.00130	42.73	56.96	0.29	0.02
27煤	7.28500	4.44600	2.81339	0.02357	0.00204	61.03	38.62	0.32	0.03
32煤	6.45000	3.91600	2.48750	0.04081	0.00569	60.71	38.57	0.63	0.09

图4 黔西戴家田煤矿基于压汞数据的龙潭组煤储层孔径分布图

Fig.4 Pore size distribution map for the Longtan Formation coal reservoir, based on mercury injection data from the Daijiatian Coal Mine in Western Guizhou

图5 黔西戴家田煤矿龙潭组煤储层低温氮气吸附-脱附曲线

Fig.5 Low-temperature nitrogen adsorption-desorption diagrams of the Longtan Formation coal reservoir from the Daijiatian Coal Mine in Western Guizhou

表5 黔西戴家田煤矿基于氮气吸附数据的龙潭组煤储层孔体积分布

Table 5 Pore volume distribution of the Longtan Formation coal reservoir, based on N2 adsorption data from the Daijiatian Coal Mine in Western Guizhou

编号	总孔体积 (cm³·g^-1)	阶段孔容(cm³·g^-1)				阶段孔容比例(%)
编号	总孔体积 (cm³·g^-1)	微孔	小孔	中孔	大孔	微孔	小孔	中孔	大孔
6煤	0.00323	0.00152	0.00130	0.00041	0	47.06	40.25	12.69	0
14煤	0.00382	0.00238	0.00113	0.00031	0	62.30	29.58	8.12	0
16煤	0.00290	0.00140	0.00114	0.00036	0	48.28	39.31	12.41	0
27煤	0.00410	0.00258	0.00120	0.00032	0	62.93	29.27	7.80	0
32煤	0.00349	0.00229	0.00108	0.00012	0	65.62	30.95	3.44	0

表6 黔西戴家田煤矿基于氮气吸附数据的龙潭组煤储层比表面积分布

Table 6 Specific surface area distribution of the Longtan Formation coal reservoir, based on N2 adsorption data from the Daijiatian Coal Mine in Western Guizhou

编号	比表面积 (m²·g^-1)	阶段比表面积(m²·g^-1)				阶段比表面积比例(%)
编号	比表面积 (m²·g^-1)	微孔	小孔	中孔	大孔	微孔	小孔	中孔	大孔
6煤	1.46121	1.21187	0.23800	0.01134	0	82.94	16.29	0.78	0
14煤	2.41003	2.16755	0.23657	0.00591	0	89.94	9.82	0.25	0
16煤	1.34629	1.12677	0.20964	0.00988	0	83.69	15.57	0.73	0
27煤	2.56813	2.32652	0.23526	0.00635	0	90.59	9.16	0.25	0
32煤	2.08237	1.77562	0.29951	0.00724	0	85.27	14.38	0.35	0

图6 黔西戴家田煤矿基于低温氮气吸附数据的龙潭组煤样孔径分布图

Fig.6 Pore size distribution map of the Longtan Formation coal reservoir, based on low-temperature N2 adsorption data from the Daijiatian Coal Mine in WesternGuizhou

表7 黔西戴家田煤矿龙潭组煤储层不同孔径孔容分布

Table 7 Pore volume distribution of pore sizes in the Longtan Formation coal reservoir from the Daijiatian Coal Mine in Western Guizhou

编号	总孔体积 (cm³·g^-1)	阶段孔容(cm³·g^-1)				阶段孔容比例(%)
编号	总孔体积 (cm³·g^-1)	微孔	小孔	中孔	大孔	微孔	小孔	中孔	大孔
6煤	0.01612	0.00152	0.00250	0.0075	0.0046	9.43	15.51	46.53	28.54
14煤	0.00851	0.00238	0.00203	0.0024	0.0017	27.97	23.85	28.20	19.98
16煤	0.00544	0.00140	0.00204	0.0014	0.0006	25.74	37.50	25.74	11.03
27煤	0.00778	0.00258	0.00200	0.0016	0.0016	33.16	25.71	20.57	20.57
32煤	0.01192	0.00229	0.00173	0.0027	0.0034	19.21	14.51	22.65	28.52

图7 黔西戴家田煤矿龙潭组煤储层总孔体积和比表面积全孔径分布直方图 (a)—(e)总孔体积全孔径分布直方图;(f)—(j)比表面积全孔径分布直方图

Fig.7 Histograms of the full pore size distribution for the Longtan Formation coal reservoir from the Daijiatian Coal Mine in Western Guizhou

表8 黔西戴家田煤矿龙潭组煤储层不同孔径比表面积分布

Table 8 Specific surface area distribution of pore sizes in the Longtan Formation coal reservoir of the Daijiatian Coal Mine in Western Guizhou

编号	比表面积 (m²·g^-1)	阶段比表面积(m²·g^-1)				阶段比表面积比例(%)
编号	比表面积 (m²·g^-1)	微孔	小孔	中孔	大孔	微孔	小孔	中孔	大孔
6煤	1.61047	1.21187	0.29510	0.09869	0.00481	75.25	18.32	6.13	0.30
14煤	2.46641	2.16895	0.26213	0.03321	0.00212	87.94	10.63	1.35	0.09
16煤	1.39939	1.12677	0.25115	0.02017	0.00130	80.52	17.95	1.44	0.09
27煤	2.62820	2.32652	0.27607	0.02357	0.00204	88.52	10.50	0.90	0.08
32煤	2.15487	1.77562	0.33275	0.04081	0.00569	82.40	15.44	1.89	0.26

图8 黔西戴家田煤矿龙潭组煤储层CH4吸附曲线图

Fig.8 CH4 adsorption diagram for the Longtan Formation coal reservoir of the Daijiatian Coal Mine in Western Guizhou

图9 黔西戴家田煤矿龙潭组煤储层孔隙比表面积与CH4最大吸附气量关系图 (a)微孔比表面积与最大吸附气量关系;(b)小孔比表面积与最大吸附气量关系;(c)中孔比表面积与最大吸附气量关系;(d)大孔比表面积与最大吸附气量关系

Fig.9 Relationship between pore surface area and maximum CH4 adsorption in the Longtan Formation coal reservoir of the Daijiatian Coal Mine in Western Guizhou

图10 黔西戴家田煤矿龙潭组煤储层孔隙比表面积与现场解吸气量关系图 (a)微孔比表面积与现场解吸气量关系;(b)小孔比表面积与现场解吸气量关系;(c)中孔比表面积与现场解吸气量关系;(d)大孔比表面积与现场解吸气量关系

Fig.10 Relationship between pore surface area and on-site desorption volume in the Longtan Formation coal reservoir of the Daijiatian Coal Mine in Western Guizhou

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