烟道气驱替石英狭缝孔中页岩气的分子模拟

Molecular simulation of the displacement of shale gas in quartz slit by flue gas

钱英强 杨雪 刘晓强 李美俊 陈泽琴 薛英

QIAN Yingqiang YANG Xue LIU Xiaoqiang LI Meijun CHEN Zeqin XUE Ying

成都理工大学 材料与化学化工学院, 成都 610059 四川轻化工大学 化学与环境工程学院, 四川 自贡 643000 中国石油大学(北京) 地球科学学院, 北京 102249 四川大学 化学学院, 成都 610064

College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu, Sichuan 610059, China College of Chemistry and Environmental Engineering, Sichuan University of Science & Engineering, Zigong, Sichuan 643000, China College of Geosciences, China University of Petroleum, Beijing 102249, China College of Chemistry, Sichuan University, Chengdu, Sichuan 610064, China

为了探究石英狭缝孔中烟道气封存联合页岩气采收技术的效率，采用巨正则蒙特卡洛(GCMC)和分子动力学(MD)模拟探讨了地质埋深、地层水含量和烟道气注入比例对烟道气(CO2/N2)驱替石英狭缝孔中页岩气(CH4)效率的影响。通过系统分析各组分的密度分布、负载量、吸附热和相互作用能，确定了各组分的吸附机理和CH4的采收率。混合组分中CH4和N2的负载量(ΓCH4和ΓN2)与地层水含量呈负相关。随着地质埋深的增大，ΓCH4和ΓN2迅速增大，在埋深达到2 400 m后趋于平缓。CO2的负载量(ΓCO2)在埋深2 400 m出现最大值；在埋深小于2 400 m时，ΓCO2与地层水含量呈正相关；埋深大于2 400 m后，ΓCO2与地层水含量呈负相关。CH4的采收率在埋深400~600 m处出现最大值，并随烟道气中CO2摩尔分数的增大而增大，表明烟道气中的CO2对CH4有较强的驱替能力。

To study the efficiency of flue gas sequestration with enhanced shale gas recovery in quartz slit, Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) simulations were adopted to investigate the influence of burial depth, formation water content and the injection ratio of flue gas on the recovery efficiency of shale gas (CH4) in quartz slit by flue gas (CO2/N2). The density distribution, loading, adsorption heat and interaction energy of each component were systematically analyzed to reveal their adsorption mechanisms and the recovery efficiency of CH4. It indicates that the loadings of mixed CH4 and N2 (ΓCH4 and ΓN2) exhibit negative correlation with formation water content. With the increasing burial depth, both ΓCH4 and ΓN2 increase at first and then tend to be constant when the burial depth is over 2 400 m. The maximum loading of CO2 (ΓCO2) occurs at the burial depth of 2 400 m. There is a positive correlation of ΓCO2 with formation water content when the burial depth is below 2 400 m, and a negative correlation when the burial depth is over 2 400 m. The recovery efficiency of CH4 (η) reaches the maximum point at the burial depth of 400-600 m, which increases with the increasing mole fraction of CO2 in flue gas, showing that CO2 in flue gas can promote the displacement of CH4 significantly.

四川省科技计划项目 2020YJ0342;四川省自然科学基金 2022NSFSC0182

https://doi.org/10.11781/sysydz202303560