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。

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.