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

doi:10.19657/j.geoscience.1000-8527.2023.091

Abstract

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

CLC Number:

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.

Figures/Tables 18

References 37

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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

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

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

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

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