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CH_4和CO_2在不同湿度页岩干酪根中的吸附行为对页岩CO_2埋存具有重要指导意义。本文采用分子动力学(MD)方法构建和优化干燥的干酪根模型,采用巨正则蒙托卡罗(GCMC)方法构建不同湿度含量的干酪根模型,并模拟CH_4、CO_2单组分及其混合气体在干酪根模型中的吸附行为。通过分析湿度对CH_4和CO_2吸附量、等量吸附热和吸附选择性的影响,对页岩CO_2埋存提高气体采收率的潜在可行性进行了探讨。研究发现:(1)水分子在高湿度下易形成笼形团簇结构,恶化CO_2置换CH_4的效果;(2)页岩CO_2埋存提高CH_4采收率在低储层压力条件下开发效果更好;(3)CO_2置换CH_4的效果在低湿度下随湿度含量增加而得到改善,对于干酪根成熟度较高的页岩储层,可考虑在气藏开发后期注入CO_2和一定水蒸气含量的混合物。
The adsorption behavior of CH_4 and CO_2 in kerogen with different moisture contents is of great guiding significance for the storage of shale CO_2. In this paper, a dry kerogen model was constructed and optimized by using molecular dynamics (MD) method. The kerogen model with different humidity contents was constructed by GCM method. The single component of CH 4, CO 2 and its mixed gas Adsorption behavior in kerogen model. By analyzing the influence of humidity on the adsorption amount of CH 4 and CO 2, the adsorption heat of the same amount and the selectivity of adsorption, the potential feasibility of enhancing the gas recovery by burying CO 2 in shale was discussed. It is found that: (1) the water molecules tend to form caged cluster structure under high humidity, deteriorating the effect of CO 2 replacement for CH 4; (2) shale CO 2 storage increases CH 4 recovery efficiency under low reservoir pressure conditions (3) The effect of CO_2 replacement of CH_4 is improved with the increase of humidity at low humidity. For shale reservoirs with high kerogen maturity, the injection of CO_2 and certain water vapor content mixture.