Yang Feng, Liu Yasong, Nie Sijia, Zheng He
Hubei Key Laboratory of Oil and Gas Exploration and Development Theory and Technology (China University of Geosciences), Wuhan 430074, China.
State Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum (Beijing), Beijing 102249, China.
Langmuir. 2025 Feb 4;41(4):2191-2204. doi: 10.1021/acs.langmuir.4c03561. Epub 2025 Jan 18.
The strong solid-liquid interaction leads to the complicated occurrence characteristics of shale oil. However, the solid-liquid interface interaction and its controls of the occurrence state of shale oil are poorly understood on the molecular scale. In this work, the adsorption behavior and occurrence state of shale oil in pores of organic/inorganic matter under reservoir conditions were investigated by using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The adsorption potential energy and interaction energy were quantitatively evaluated, and the control mechanism of the oil-rock interaction on shale oil occurrence was explained. Results show that the density distribution of shale oil is not uniform under the confined space. Multiple layers of adsorption of -octane occur in graphene pores. The number of adsorbed layers is mainly affected by pore size. With the increasing temperature and pore size, the adsorption site shifts from the high-energy to low-energy site and the solid-liquid interaction weakens. The effect of pressure on the occurrence state can be ignored due to capillary condensation. Minerals and oil chemical compositions also affect the oil-rock interaction and occurrence state. The adsorption intensity of minerals to -octane decreases in the order graphene > montmorillonite > quartz. Competitive adsorption occurs among oil components. The adsorption order of oil components in graphene is asphaltenes > resin > nonhydrocarbon compound > aromatic hydrocarbons > saturated hydrocarbons. Asphaltenes preferentially adsorb on the surface of organic matter and occupy most of the adsorption surface, while saturated hydrocarbons mainly adsorb on the surface of heavy components or distribute in the pore center. The molecular structure of hydrocarbons also affects the adsorption characteristics. The long-chain hydrocarbons preferentially adsorb on the surface more than short-chain hydrocarbons. The straight-chain hydrocarbons preferentially adsorb more than the branched-chain hydrocarbons. This study provides the microscopic interaction between shale oil and minerals and explores the effect of the control mechanism of the oil-rock interfacial interaction on the occurrence state at the molecular level.
强烈的固液相互作用导致了页岩油复杂的赋存特征。然而，在分子尺度上，固液界面相互作用及其对页岩油赋存状态的控制尚不清楚。在这项工作中，通过使用巨正则蒙特卡罗（GCMC）和分子动力学（MD）模拟，研究了储层条件下页岩油在有机/无机物质孔隙中的吸附行为和赋存状态。定量评估了吸附势能和相互作用能，并解释了油岩相互作用对页岩油赋存的控制机制。结果表明，在受限空间下页岩油的密度分布不均匀。石墨烯孔隙中出现了多层正辛烷吸附。吸附层数主要受孔径影响。随着温度和孔径的增加，吸附位点从高能位点向低能位点转移，固液相互作用减弱。由于毛细管凝聚，压力对赋存状态的影响可以忽略不计。矿物和油的化学成分也影响油岩相互作用和赋存状态。矿物对正辛烷的吸附强度按石墨烯＞蒙脱石＞石英的顺序降低。油组分之间存在竞争吸附。石墨烯中油组分的吸附顺序为沥青质＞树脂＞非烃化合物＞芳烃＞饱和烃。沥青质优先吸附在有机质表面并占据大部分吸附表面，而饱和烃主要吸附在重组分表面或分布在孔隙中心。烃类的分子结构也影响吸附特性。长链烃比短链烃更优先吸附在表面。直链烃比支链烃更优先吸附。本研究揭示了页岩油与矿物之间的微观相互作用，并在分子水平上探索了油岩界面相互作用控制机制对赋存状态的影响。
