Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide-Moisture Conditions: A Molecular Dynamic Study
Mechanism Analysis of Shale Gas Adsorption under Carbon Dioxide-Moisture Conditions: A Molecular Dynamic Study
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二氧化碳—水分条件下页岩气吸附机理分析：分子动力学研究
DOI：
10.1021/acs.energyfuels.2c03244
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发表时间：
2022-11-23
期刊：
影响因子：
5.3
通讯作者：
Sun, Shuyu
中科院分区：
文献类型：
--
作者：
Liu, Jie;Zhang, Tao;Sun, Shuyu
近几十年来，一直被视为清洁能源的页岩气正逐步取代常规能源。页岩气在CO2-水分体系中的吸附已被许多研究所讨论，但其内在机理尚未阐明。采用分子动力学方法研究页岩气在干酪根纳米缝中的吸附行为。页岩气及各组分的空间密度分布具有很强的不均匀性。为揭示页岩气在不同靶位上的非均相吸附机理，首次计算了页岩气组分在不同靶位上的平均力势（PMF）分布。水（H2O）组分更倾向于吸附在富氧位置上，这是由于强分子极性和氢键相互作用的结果。CO2组分倾向于吸附在富碳位点上，这是货车德瓦尔斯相互作用和分子极性与干酪根壁结合的结果。势能等值线的计算，以验证不同的组分和干酪根表面之间的亲和力，和势能差可以观察到之间的体相和吸附相，这对应于密度和PMF分析。并进行了敏感性分析，验证了上述机理解释。温度越高，页岩气的解吸越容易，压力越高，页岩气的吸附量越大。在较大的孔隙空间中，由于H2O和CO2分子含量较多，甲烷（CH 4）的吸附量减少。不同组分比例下的实例验证了CO2含量越高越有利于页岩气的解吸。
In recent decades, shale gas, which has been regarded as a source of clean energy, is gradually replacing conventional energy. Shale gas adsorption in carbon dioxide (CO2)-moisture systems has been discussed in many previous studies; however, the intrinsic mechanism has not been clarified yet. In this work, the molecular dynamic (MD) method is adopted to study the adsorption behaviors of shale gas adsorption in the realistic kerogen nanoslit. The spatial density distributions of shale gas and different components have strong inhomogeneity. To reveal the heterogeneous adsorption mechanism, the potential of mean force (PMF) distributions of shale gas components are calculated on different target positions for the first time. The water (H2O) component prefers to adsorb on the oxygen-enriched position, as a result of the strong molecular polarity and hydrogen bond interactions. The CO2 component tends to adsorb on the carbon-rich site, which is the result of combining the van der Waals interaction and molecular polarity with kerogen walls. The potential energy contours are computed to verify the affinities between different components and the kerogen surface, and the potential energy difference can be observed between the bulk phase and adsorbed phase, which corresponds to the density and PMF analyses. The sensitivity analysis is also carried out to verify the above mechanism explanation. Higher temperature facilitates the desorption of shale gas, and higher pressure leads to more adsorption quantity. In the larger pore space, because of more content of H2O and CO2 molecules, the adsorption amount of methane (CH4) decreases. More content of CO2 is conducive to the desorption of shale gas, verified by cases in various component proportions.