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CO2/N2二元气体对甲烷在煤中吸附影响的分子模拟研究

孙致学 闵成 张婉露 蒋永平 于雪峰 崔彬

孙致学,闵成,张婉露,等. CO2/N2二元气体对甲烷在煤中吸附影响的分子模拟研究[J]. 煤田地质与勘探,2022,50(3):127−136. doi: 10.12363/issn.1001-1986.21.11.0657
引用本文: 孙致学,闵成,张婉露,等. CO2/N2二元气体对甲烷在煤中吸附影响的分子模拟研究[J]. 煤田地质与勘探,2022,50(3):127−136. doi: 10.12363/issn.1001-1986.21.11.0657
SUN Zhixue,MIN Cheng,ZHANG Wanlu,et al. Molecular simulation of the effect of CO2/N2 binary gas on methane adsorption in coal[J]. Coal Geology & Exploration,2022,50(3):127−136. doi: 10.12363/issn.1001-1986.21.11.0657
Citation: SUN Zhixue,MIN Cheng,ZHANG Wanlu,et al. Molecular simulation of the effect of CO2/N2 binary gas on methane adsorption in coal[J]. Coal Geology & Exploration,2022,50(3):127−136. doi: 10.12363/issn.1001-1986.21.11.0657

CO2/N2二元气体对甲烷在煤中吸附影响的分子模拟研究

doi: 10.12363/issn.1001-1986.21.11.0657
基金项目: 国家自然科学基金重点项目(51774317)
详细信息
    第一作者:

    孙致学,1979年生,男,山东沂南人,博士,副教授,从事复杂油气藏精细描述与开发工作. E-mail:upcszx@upc.edu.cn

  • 中图分类号: P618.13;O647.32

Molecular simulation of the effect of CO2/N2 binary gas on methane adsorption in coal

  • 摘要: 二元气驱技术(CO2/N2-ECBM)已成为煤层气增产的重要手段,明确CO2/N2在煤层中的竞争吸附规律以及对煤层物性的影响具有重大意义。利用分子模拟软件Materials Studio建立延川南煤层气实际区块温度、压力条件下的煤分子模型。基于巨正则蒙特卡洛(GCMC)方法研究CO2/N2交替驱替煤层气技术中各注入阶段对CH4吸附的影响,明确CO2、N2对煤层孔渗物性的影响规律。结果表明:在CO2注入阶段,煤层中甲烷迅速解吸;煤中气体吸附总量上升,煤基质膨胀效应增强,导致煤的孔隙体积降低。而转N2注入后,由于N2分压作用使得CH4、CO2吸附量呈现出不同程度的降低;当ωN2/ωCO2≤0.6时煤分子中气体总吸附量迅速降低,而当N2饱和吸附后气体总吸附量保持稳定。煤层孔渗物性随着气体吸附总量呈现出迅速增大后趋于平缓的趋势。此外,ωN2/ωCO2>0.6后N2吸附率迅速降低,这会使得产出气中CH4纯度较低,导致后期提纯成本大大增加。因此,当ωN2/ωCO2=0.6左右时,CH4解吸量为最大值,煤孔隙率较高,最有利于煤层气的开发。

     

  • 图  研究区无烟煤大分子模型

    Fig. 1  Macro molecular model of anthracite in the study area

    图  无烟煤结构模型的康纳利表面

    Fig. 2  Connolly surface of the anthracite structure model

    图  模拟得到的煤对甲烷等温吸附数据及拟合曲线

    Fig. 3  Methane isothermal adsorption data and the fitting curve obtained by simulation

    图  各组分逸度随ωCO2/ωCH4变化曲线

    Fig. 4  Variation curves of the fugacity of each component with ωCO2/ωCH4

    图  各组分逸度随ωN2/ωCO2变化曲线

    Fig. 5  Variation curves of the fugacity of each component with ωN2/ωCO2

    图  煤中CH4、CO2吸附量随ωCO2/ωCH4变化曲线

    Fig. 6  Variation curves of the adsorption amount of CH4 and CO2 in coal with ωCO2/ωCH4

    图  煤中气体总吸附量随ωCO2/ωCH4变化曲线

    Fig. 7  Variation curve of the total adsorption amount of gas in coal with ωCO2/ωCH4

    图  不同ωCO2/ωCH4时煤岩孔隙结构

    Fig. 8  Pore structures of the coal and rock under different ωCO2/ωCH4

    图  煤孔隙率、渗透率随ωCO2/ωCH4变化曲线

    Fig. 9  Variation curves of coal porosity and permeability with ωCO2/ωCH4

    图  10  各组分吸附量随ωN2/ωCO2变化曲线

    Fig. 10  Variation curves of the adsorption capacity of each component with ωN2/ωCO2

    图  11  气体总吸附量随ωN2/ωCO2变化曲线

    Fig. 11  Variation curve of the total adsorption of gas with ωN2/ωCO2

    图  12  不同ωN2/ωCO2下煤的孔隙结构

    Fig. 12  Pore structures of the coal under different ωN2/ωCO2

    图  13  煤孔隙率、渗透率随ωN2/ωCO2变化曲线

    Fig. 13  Variation curves of coal porosity andpermeability with ωN2/ωCO2

    图  14  N2吸附率随ωN2/ωCO2变化曲线

    Fig. 14  Variation curve of the adsorption rate with ωN2/ωCO2

    表  1  Langmuir体积、Langmuir压力和孔隙率的拟合数据与实测数据

    Table  1  Fitting data and measured data of Langmuir volume, Langmuir pressure and porosity

    参数Langmuir体积/
    (mmol·g−1)
    Langmuir压力/
    MPa
    孔隙率/
    %
    拟合数据1.2641.0769.89
    实测数据1.2321.0699.01
    相对误差/%2.5900.6509.74
    下载: 导出CSV
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  • 收稿日期:  2021-11-16
  • 修回日期:  2022-01-19
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