不同温度下低、中、高阶煤储层甲烷吸附解吸特征差异

doi:10.13809/j.cnki.cn32-1825/te.2020.04.003

油气藏评价与开发 ›› 2020, Vol. 10 ›› Issue (4): 17-24.doi: 10.13809/j.cnki.cn32-1825/te.2020.04.003

不同温度下低、中、高阶煤储层甲烷吸附解吸特征差异

马东民^1,^2,³,高正¹(),陈跃^1,²,张辉¹,邵凯⁴,张治仓⁴,吴讯⁴,杨甫²

1.西安科技大学,陕西西安710054
2.自然资源部煤炭资源勘查与综合利用重点实验室,陕西西安710021
3.西安科技大学煤炭绿色开采地质研究院,陕西西安710054
4.陕西省煤层气开发利用有限公司,陕西西安710119

收稿日期:2019-12-31 发布日期:2020-08-07 出版日期:2020-08-26
作者简介:马东民（1967 —）,男,博士,教授,从事煤与煤层气地质教学研究。通讯地址：陕西省西安市碑林区雁塔中路58号,邮政编码：710054。E-mail： mdm6757@126.com
基金资助:
国家自然科学基金项目“润湿性制约下低阶煤不同煤岩组分甲烷解吸机制”(41902175);陕西省自然科学基础研究计划“彬长地区煤层气解吸产出过程的润湿性作用机制”(2019JQ-245);中国博士后科学基金资助项目“低煤阶镜煤与暗煤润湿性差异及对甲烷解吸的影响”(2019M653873XB);自然资源部煤炭资源勘查与综合利用重点实验室开放课题“黄陇煤田中西部煤化作用过程中煤储层孔隙系统演化规律”(KF2019-2);西安科技大学煤炭绿色开采地质研究院“低阶煤储层CH₄产出微观机理与提产工艺研究”(MTy2019-04)

Differences in methane adsorption and desorption characteristics of low, medium and high rank coal reservoirs at different temperatures

MA Dongmin^1,^2,³,GAO Zheng¹(),CHEN Yue^1,²,ZHANG Hui¹,SHAO Kai⁴,ZHANG Zhicang⁴,WU Xun⁴,YANG Fu²

1. College of Geology and Environment, Xi’an University of Science and Technology, Xi’an, Shaanxi 710054, China
2. Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Natural Resources, Xi’an, Shaanxi 710021, China
3. Geological Research Institute for Coal Green Mining, Xi’an University of Science and Technology, Xi’an, Shaanxi 710054, China
4. Shaanxi Coalbed Methane Development and Utilization Co., Ltd., Xi’an, Shaanxi 710119, China

Received:2019-12-31 Online:2020-08-07 Published:2020-08-26

摘要/Abstract

摘要：

为研究不同煤阶CH₄吸附/解吸特征差异及解吸滞后效应,采集低、中、高煤阶样品,进行显微组分测定、液氮吸附、等温吸附/解吸等实验,系统分析不同煤阶样品物质成分、孔隙结构、吸附/解吸特征差异及解吸滞后效应,结合甲烷吸附热计算结果,从能量角度探讨煤层气解吸滞后机理。结果表明：①煤样的镜质组反射率R_o,max分别为0.43 %、1.26 %、3.27 %,低阶煤样品镜质组含量低、惰质组含量高、挥发分高和固定碳高,中、高阶样品则反之;煤变质程度增高,孔隙度、BET比表面积、BJH总孔容、分形维数D₂呈“V”型变化,D₁呈倒“V”型变化;②温度相同时,煤阶越高,残余吸附量越大,解吸难度增加。温度升高,残余吸附量呈先上升后下降的趋势,以40 ℃为拐点,温度对气体分子活化程度和煤的孔隙结构均有影响;③压力相同,煤阶越高,甲烷吸附速率越快,低压阶段（p<4 MPa）,吸附量增加快,高压阶段（p>4 MPa）,吸附量增加不明显;④DFS4 ^#、SGZ11 ^#、SH3 ^#三个煤样解吸过程中等量吸附热均大于吸附过程中的等量吸附热,表明解吸过程需要持续从体系外吸收热量,而处于吸附态的甲烷由于解吸需要的等量吸附热大于吸附时的等量吸附热需要从外界环境吸取能量,吸附和解吸过程的能量差异会导致解吸滞后;处于游离态的甲烷,由于高压作用下进入微小孔,致使煤基质膨胀变形,孔隙结构改变,导致甲烷解吸受限,造成解吸滞后。

关键词: 变质程度, 等温吸附, 等压吸附, 分形维数, 吸附热, 解吸滞后

Abstract:

In order to study the difference in adsorption/desorption characteristics and the desorption hysteresis of CH₄ in different coal ranks, low, medium, and high coal rank samples are collected for the experiments of micro-component determination, liquid nitrogen adsorption, and isothermal adsorption/desorption to systematically analyze the composition, pore structure, differences in adsorption/desorption characteristics and desorption hysteresis effects of different coal rank sample materials. Combined with the calculation results of methane adsorption heat, the mechanism of coalbed methane desorption hysteresis from the energy perspective is discussed. The results show that: ①The reflectance R_o,max of the vitrinite group of coal samples are 0.43 %, 1.26 %, and 3.27 %, respectively. Low-rank coal samples have low vitrinite group content, high inert matter group content, high volatile content and fixed carbon. Medium-rank and high-rank samples are reversed. The degree of coal metamorphism increases. Porosity, BET specific surface area, BJH total pore volume, and fractal dimension D₂ change in a “V” shape, and D₁changes in an inverted “V” shape. ②Under isothermal condition, the residual adsorption amount becomes larger as the coal rank rises, and the desorption becomes more difficult. As the temperature rises, the residual adsorption capacity increases first and then decreases. With 40 ℃ as the inflection point, the temperature influences both the degree of activation of gas molecules and the pore structure of coal. ③When the pressure is the same, the higher the coal rank, the faster the methane adsorption rate at the low-pressure stage（p<4 MPa）, the adsorption capacity increases rapidly at the high-pressure stage（p>4 MPa）, and the adsorption capacity does not increase significantly. ④For the three coal samples, DFS4 ^#, SGZ11 ^#, and SH3 ^#, in the desorption process, their isosteric heat of adsorption are all greater than that in the adsorption process, indicating that the desorption process needs to continuously absorb heat from outside. Therefore, the methane in the adsorption state needs to absorb energy from the external environment, and the energy difference between the adsorption and desorption processes will cause desorption hysteresis. The methane in the free state enters into the micropores due to high pressure, resulting in the expansion and deformation of coal matrix, changes in pore structure, limit of methane desorption, and finally a desorption hysteresis effect.

Key words: metamorphic degree, isothermal adsorption, isobaric adsorption, fractal dimension, adsorption heat, desorption hysteresis

中图分类号:

TE132.2

马东民,高正,陈跃等. 不同温度下低、中、高阶煤储层甲烷吸附解吸特征差异[J]. 油气藏评价与开发, 2020, 10(4): 17-24.

Dongmin MA,Zheng GAO,Yue CHEN, et al. Differences in methane adsorption and desorption characteristics of low, medium and high rank coal reservoirs at different temperatures[J]. Reservoir Evaluation and Development, 2020, 10(4): 17-24.

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煤样	煤阶	R_o,max	显微煤岩组分含量
煤样	煤阶	R_o,max	镜质组	惰质组	壳质组	矿物质
DFS4^#煤	CY	0.43	22.8	68.1	2.2	6.9
SGZ11^#煤	JM	1.26	69.8	14.2	0	16.0
SH3^#煤	WY	3.27	61.8	29.6	0	8.6

煤样	煤阶	R_o,max	工业分析
煤样	煤阶	R_o,max	水分（M_ad）	灰分（A_d）	挥发分（V_daf）	固定碳（FC_ad）
DFS4^#煤	CY	0.43	4.65	15.74	32.95	46.66
SGZ11^#煤	JM	1.26	0.96	6.94	16.62	75.48
SH3^#煤	WY	3.27	3.55	13.64	6.38	76.43

煤样	BET比表面积/（m²·g^-1）	各孔径段比表面积比/%			BJH孔容/ （mL·g^-1）	各孔径段孔孔容比/%
煤样	BET比表面积/（m²·g^-1）	<10 nm	10~100 nm	>100 nm	BJH孔容/ （mL·g^-1）	<10 nm	10~100 nm	>100 nm
DFS4^#	11.46	90.51	9.25	0.24	0.019	47.47	43.37	9.16
SGZ11^#	0.34	81.51	17.58	0.91	0.001	30.00	54.00	16.00
SH3^#	2.04	95.30	4.66	0.04	0.002	67.61	26.72	5.67

煤样	A₁	D₁=A₁+3	A₂	D₂=A₂+3
DFS4^#	-0.71	2.29	-0.25	2.75
SGZ11^#	-0.65	2.35	-0.35	2.65
SH3^#	-0.73	2.27	-0.11	2.89

煤样	平衡水含量/ %	温度/ ℃	Langmuir拟合			解吸式拟合
煤样	平衡水含量/ %	温度/ ℃	a_a	b_a	R²	a_d	b_d	c	R²
DFS4^#	10.14	25	11.563	0.448	0.992	8.623	0.701	0.949	0.996
		30	11.566	0.396	0.990	8.341	0.619	0.994	0.997
		35	11.079	0.382	0.993	8.040	0.597	0.973	0.998
		40	10.725	0.374	0.993	7.698	0.543	1.039	0.999
		45	10.238	0.382	0.993	7.380	0.568	1.009	0.998
SGZ11^#	3.01	25	16.370	0.513	0.998	14.130	0.807	0.930	0.995
		30	15.730	0.506	0.998	13.380	0.801	1.020	0.997
		35	15.210	0.493	0.997	12.330	0.795	1.490	0.995
		40	14.730	0.487	0.997	11.720	0.811	1.570	0.993
		45	13.890	0.486	0.999	11.390	0.791	1.210	0.991
SH3^#	4.19	25	37.030	0.430	0.998	29.850	0.721	3.250	0.995
		30	35.240	0.410	0.998	27.860	0.715	3.290	0.992
		35	33.970	0.370	0.997	25.920	0.706	3.340	0.993
		40	32.450	0.340	0.997	23.760	0.695	3.560	0.994
		45	30.910	0.310	0.999	22.320	0.687	3.120	0.996

不同温度下低、中、高阶煤储层甲烷吸附解吸特征差异

Differences in methane adsorption and desorption characteristics of low, medium and high rank coal reservoirs at different temperatures

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