Oil diffusion in shale nanopores: Insight of molecular dynamics simulation
Oil diffusion in shale nanopores: Insight of molecular dynamics simulation
复制标题
页岩纳米孔中的石油扩散：分子动力学模拟的见解
DOI：
10.1016/j.molliq.2019.111183
复制
发表时间：
2019
影响因子：
6
通讯作者：
Xing Xiangdong
中科院分区：
文献类型：
--
作者：
Zhang Wei;Feng Qihong;Wang Sen;Xing Xiangdong
页岩含有各种矿物质。油气在有机质、无机质和粘土矿物中的赋存状态和运移机理存在显著差异。在这项研究中，研究了油在由各种矿物类型组成的页岩纳米孔隙中的扩散率。讨论了孔隙大小、温度、压力、烷烃类型、矿物类型和含水量对页岩油扩散的影响。结果显示，页岩纳米孔中辛烷的扩散系数约为10− 9 m/s2。有机质对石油的吸附量是无机组分和粘土矿物的近2倍。由于有机物表面的超光滑结构，油的扩散系数按有机物>无机物>粘土矿物的顺序依次减小。油的扩散系数随着孔径的增大和温度的升高而增大。长链烷烃由于分子量大，分子间作用力大，扩散系数较弱。与短链烷烃相比，温度对长链烷烃扩散的影响较小。水的存在抑制了油在各种材料组成的孔隙中的吸附和扩散。油扩散系数的阻水效应在有机孔隙中更为显著，因为水在有机孔隙中以团簇形式聚集，形成活塞式过程，而在无机材料表面则形成水膜。研究结果揭示了油在页岩纳米孔隙中的扩散行为，为页岩油勘探开发提供了理论支持。
Shale contains various minerals. The occurrence behavior and flow mechanism of gas and oil in organic matters, inorganic material and clay minerals have significant differences. In this study, the diffusivity of oil in shale nanopores composed by various mineral types were investigated. The effects of pore size, temperature, pressure, alkane types, mineral types and moisture content on shale oil diffusion were discussed. The results revealed that the diffusion coefficients of octane in shale nanopores were on the order of 10−9m/s2. The adsorption amount of oil in organic matters was almost two folds larger than that in inorganic composition and clay minerals. However, the diffusivity of oil decreases in the order of organic matter, inorganic material and clay mineral due to the ultrasmooth structure of organic surface. The oil diffusivity increased with the increase of pore size and temperature. Long chain alkane presented a weaker diffusivity due to the larger molecular weight and intermolecular forces. The temperature effect on long chain alkane diffusion was less evident comparing with shorter chain alkane. The existence of water inhibited the adsorption and diffusion of oil in the pores composed by all kinds of materials. The water inhibiting effect of oil diffusivity was much more significant in organic pores since the water accumulated as cluster in organic slit, providing a piston-like process, while a water film was presented on the surface of inorganic materials. The findings of this study revealed the oil diffusion behavior in shale nanopores and provided the theoretical support for shale oil exploration and development.