油气藏评价与开发 ›› 2025, Vol. 15 ›› Issue (4): 579-588.doi: 10.13809/j.cnki.cn32-1825/te.2025.04.006

• 方法理论 • 上一篇    下一篇

重质烷烃对页岩中CO2与CH4竞争吸附的影响机制

张欢1(), 柴昊楠1, 赵洪宝2, 杜双利1(), 李义涛3   

  1. 1.太原理工大学安全与应急管理工程学院,山西 太原 030024
    2.中国矿业大学(北京)能源与矿业学院,北京 100083
    3.太原理工大学矿业工程学院,山西 太原 030024
  • 收稿日期:2024-07-08 发布日期:2025-07-19 出版日期:2025-08-26
  • 通讯作者: 杜双利(1990—),女,博士,讲师,主要从事计算化学和分子模拟方向的研究。地址:山西省太原市万柏林区迎泽西大街79号,邮政编码:030024。E-mail: dsljoyful@163.com
  • 作者简介:张欢(1991—),男,博士,副教授,主要从事安全工程及非常规天然气开采方向的研究。地址:山西省太原市万柏林区迎泽西大街79号,邮政编码:030024。E-mail: zhanghuanvip01@163.com
  • 基金资助:
    国家自然科学基金项目“局部动载扰动下煤岩微细观结构演化特性与增透机理研究”(52004170);山西省科技厅面上基金项目“煤分子结构与气体环境对煤尘爆炸影响的全景式分子作用机制”(202303021211071);山西省科技厅面上基金项目“非均匀动力扰动下煤岩结构损伤特性及其渗流演化机制研究”(202303021221008)

Mechanism of heavy alkane influence on CO2 and CH4 competitive adsorption in shale

ZHANG Huan1(), CHAI Haonan1, ZHAO Hongbao2, DU Shuangli1(), LI Yitao3   

  1. 1.College of Safety and Emergency Management Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024, China
    2.School of Energy and Mining Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China
    3.College of Mining Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024, China
  • Received:2024-07-08 Online:2025-07-19 Published:2025-08-26

摘要:

页岩气储层中CH4往往与C2H6、C3H8等重质烷烃并存,为探究页岩有机纳米孔中重质烷烃对CH4与CO2竞争吸附的影响机制,基于密度泛函理论和巨正则蒙特卡洛方法,从吸附能、结构特性、弱作用分析及等温吸附等方面分别研究了气体与干酪根之间相互作用的类型及强度,纯组分气体的吸附性能,不同含量的C2H6和C3H8对CH4吸附性能的影响,以及对CO2与CH4竞争吸附的影响。结果表明:①随着烷烃碳链的延长,气体与干酪根之间的相互作用强度逐渐增强,CH4、C2H6、C3H8、CO2 4种气体分子在干酪根表面的吸附能大小顺序为C3H8>C2H6>CO2>CH4;②单组分气体吸附中,从CH4到C3H8,由于单个烷烃占据的吸附位点增加,气体的总吸附量降低,CO2较大的吸附量与其几何结构有关;③随着系统温度升高,气体分子吸附量均有所下降,随着系统压力增大,气体吸附量增幅均逐渐减弱;④在二元混合吸附中,C2H6和C3H8的存在使CH4的吸附量明显降低,且C3H8的影响更为显著,同时,CO2的存在也使CH4的吸附量大幅降低;⑤三元混合吸附中,C2H6、C3H8与CO2的共存对促进CH4解吸具有协同作用,当C2H6和C3H8质量分数分别占混合气体质量分数的4%和8%时可获得最有效的促进CH4增产的效果。此外,与C3H8相比,C2H6的存在更有利于CO2封存。研究结果可为页岩气多组分竞争吸附以及注CO2开采提供理论支撑。

关键词: 干酪根, 多组分页岩气, 竞争吸附, 计算化学, 分子模拟

Abstract:

In shale gas reservoirs, CH4 often coexists with heavy alkanes such as C2H6 and C3H8. To investigate the mechanism by which heavy alkanes affect the competitive adsorption of CH4 and CO2 in organic nanopores of shale, this study combines density functional theory and Grand Canonical Monte Carlo simulations. The interaction types and strengths between gas molecules and kerogen were systematically analyzed in terms of adsorption energy, structural characteristics, weak interaction analysis, and isothermal adsorption. The adsorption performance of pure-component gases was examined, followed by an evaluation of the influence of varying C2H6 and C3H8 concentrations on CH4 adsorption performance. Furthermore, the influence of C2H6 and C3H8 on CO2 and CH4 competitive adsorption was analyzed. The results showed that: (1) With the elongation of alkane carbon chains, the interaction strength between gas molecules and kerogen progressively intensified. The adsorption energies of the four gas molecules on the kerogen surface followed the order: C3H8>C2H6>CO2>CH4. (2) For single-component gas adsorption, the total adsorption capacity decreased from CH4 to C3H8 due to the increased adsorption sites occupied by individual alkanes. Meanwhile, CO2 exhibited a higher adsorption capacity, which was attributed to its unique geometric structure. (3) With rising system temperature, the adsorption capacity of various gas molecules declined. As system pressure increased, the incremental rise in gas adsorption capacity gradually diminished. (4) In binary mixture adsorption, the existence of C2H6 and C3H8 significantly reduced the CH4 adsorption capacity, with C3H8 exhibiting a more significant effect. Meanwhile, the addition of CO2 greatly decreased CH4 adsorption capacity. (5) In ternary mixture adsorption, the coexistence of C2H6, C3H8, and CO2 demonstrated a synergistic effect on promoting CH4 desorption. Specifically, the most effective promotion of CH4 production was achieved when C2H6 and C3H8 accounted for 4% and 8% of the total gas mixture by mass. In addition, compared with C3H8, C2H6 was more favorable to the storage of CO2. These findings provide theoretical support for multicomponent competitive adsorption in shale gas and for CO2-enhanced shale gas extraction.

Key words: kerogen, multicomponent shale gas, competitive adsorption, computational chemistry, molecular simulation

中图分类号: 

  • TE377