揭示储层环境与烃类组分对高岭石孔隙中流体行为的关键影响
Revealing crucial effects of reservoir environment and hydrocarbon fractions on fluid behaviour in kaolinite pores
AI总结：
本研究通过分子模拟探究高岭石两种基面与不同烃类的相互作用，明确烃类结构、官能团及温压条件对吸附、扩散等流体行为的影响规律，揭示了不同组分的吸附强度排序与表面分布差异。
摘要：
烃类（HCs）与黏土表面的相互作用决定了页岩储层内的流体行为，这类相互作用会受到烃类组分多样性及环境条件变化的影响。本研究考察了具有两种不同基面的高岭石黏土与一系列烃类之间的相互作用，评估了不同分子结构、官能团以及环境条件（聚焦于储层温度和压力范围）对烃类的吸附选择性、表面堆积、分子排列与取向以及扩散行为的影响。通过分子相互作用能分析，定量阐明了烃类在不同高岭石表面的吸附机制。研究结果表明，分子构型、官能团和空间效应决定了烃类在不同高岭石表面的分布模式。不同烃类与高岭石的相互作用能差异显示，不同烃类的吸附强度顺序为：沥青质>杂原子烃类>饱和烃类>芳香烃类。此外，研究发现吸附特性具有高度温度敏感性：温度升高会显著降低吸附量。超过特定阈值后，压力升高对烃类流体行为的影响不可忽略，且该影响与分子堆积及流动性降低相关。基于实际地质特征的模拟结果显示，受竞争吸附和黏土表面相互作用的影响，不同烃类组分在不同高岭石表面存在显著的吸附差异。极性表面主要被杂原子烃类占据，而在非极性表面，沥青质和重质饱和烃类会形成多层吸附结构，分子平行于表面排列。
英文摘要：
Interactions of hydrocarbons (HCs) and clay surfaces are responsible for fluid behaviour within shale reservoirs. These interactions are affected by the diversity of HC components and the variations in environmental conditions. This study examines the interactions between kaolinite clay, featuring two distinct basal surfaces, and an array of HCs. We assess the impact of various molecular structures, functional groups, and environmental conditions (focusing on the reservoir temperature and pressure ranges) on the adsorption selectivity, surface packing, molecular alignment and orientation, and diffusion of HCs. Analyses of molecular interaction energies provide a quantitative elucidation of the adsorption mechanisms of HCs on the different kaolinite surfaces. Our findings suggest that molecular configuration, functional groups, and spatial effects dictate the distribution patterns of HCs for the different kaolinite surfaces. The differences in the interaction energy between various HCs with kaolinite reveal the adsorption strength of different HCs in the order of asphaltenes>heteroatomic HCs>saturated HCs>aromatic HCs. Furthermore, we observe that the adsorptive characteristics are highly temperature-sensitive; with increased temperatures markedly reducing the adsorption amount. Beyond a certain threshold, the effect of pressure rise on the fluid behaviour of HCs is non-negligible and is related to molecular packing and reduced mobility. Simulation results based on actual geological characteristics demonstrate notable adsorption disparities among hydrocarbon components on different kaolinite surfaces, influenced by competitive adsorption and clay surface interactions. Polar surfaces are predominantly occupied by heteroatomic HCs, whereas on non-polar surfaces, asphaltenes and heavy saturated HCs develop multi-layer adsorption structures, with molecules aligned parallel to the surface.
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