基于分子模拟的煤层CH_4解吸规律研究  

CH_4 desorption rule in coalbed based on molecule simulation

作　　者：杨兆中[1] 徐鸿涛[1] 付嫱[2] 李小刚[1] 范立晶 刘敏[4] 

机构地区：[1]西南石油大学油气藏地质及开发工程国家重点实验室,四川成都610500 [2]西南油气田分公司采气工程研究院,四川广汉618300 [3]中国石油川庆钻探国际工程公司,四川成都610500 [4]中国石化西南工程有限公司井下作业公司,四川德阳618000

出　　处：《油气藏评价与开发》2016年第5期67-71,共5页Petroleum Reservoir Evaluation and Development

基　　金：国家科技重大专项"深煤层煤层气增产改造技术"(2011ZX05042-002-001)

摘　　要：利用分子模拟方法，研究了煤储层中甲烷在不同狭缝孔中的解吸状态，讨论温度、压力和孔径与CH4解吸量的关系。结果表明，在较低温度范围内，温度变化对CH4的解吸影响不明显，在现场中若用升温的方式促进CH4解吸，需大幅度提高温度。降压可以促进CH4解吸，但不能达到开采微孔中CH4的效果。在微孔中，壁面叠加效应的影响，对比CH4分子在1 nm与2 nm孔径中的吸附热可知，CH4在孔径为1 nm左右的孔隙中解吸相对困难。随着孔径的增大，2~9 nm的绝对吸附量解吸率逐渐增加，增加幅度依次降低。说明在孔径大于2 nm后，自由空间体积是决定总吸附量大小的主要因素，呈吸附态的气体量稳定在一定范围内，这对CH4的扩散和渗流有着重要意义。Molecule simulation is adopted to study CH4 desorption state in different slit carbon pores and discuss the relation among temperature, pressure, pore diameter and CH4 desorption. The result shows that, in low temperature, the changing temperature has little influence on CH4 desorption, in addition, if heating way is adopted to accelerate CH4 desorption, it needs greatly improve temperature. Decompression can accelerate CH4 desorption, but it can’t achieve the effect of recovering CH4 in micropores. Furthermore, by comparing the adsorption heat in 1 nm and 2 nm pores, it indicates that CH4 desorption is relatively difficult in 1 nm pores because of the wall superimposed effect. As the pore size increases, the CH4 absolute adsorption desorption rate in 2 nm to 9 nm pores increases relatively and the increase of CH4 adsorption reduces gradually. When the pore size is larger than 2 nm, the free volume is the main reason that decides the total adsorption capacity, and excess adsorption capacity will keep in a certain range. The research has important significance for CH4 diffusion and seepage.

关 键 词：煤层气 孔径 解吸 分子模拟 

分 类 号：TE122[石油与天然气工程—油气勘探]