纳米限域下页岩中可溶有机质的非均质性及页岩油赋存状态  

Heterogeneity of soluble organic matter in shale and occurrence state of shale oil under nanoconfinement

作　　者：洪智宾 吴嘉 方朋 余进洋 伍正宇 于佳琦 HONG Zhibin;WU Jia;FANG Peng;YU Jinyang;WU Zhengyu;YU Jiaqi(College of Geosciences,China University of Petroleum(Beijing),Beijing 102249,China)

机构地区：[1]中国石油大学(北京)地球科学学院,北京102249

出　　处：《岩性油气藏》2024年第6期160-168,共9页Lithologic Reservoirs

基　　金：国家自然科学基金“中低成熟度陆相页岩油资源形成与原位转化开采机理”(编号:U22B6004)资助。

摘　　要：以渤海湾盆地古近系沙河街组三段页岩储层中—低熟页岩油的族组分组成为例,通过分子动力学模拟构建了纳米尺度的页岩可溶有机质体系模型,对地层条件下页岩可溶有机质体系在纳米尺度空间中的分子赋存状态进行了研究,并对页岩油可动性限制因素进行了分析。研究结果表明:①页岩可溶有机质体系模型由饱和烃、芳香烃、非烃、沥青质4类族组分和水组成,质量分数分别为18.6%,18.9%,19.7%,38.6%和4.2%,4类族组分的代表分子分别为nC_(18),1-甲基菲,一个带有含羧基的长侧链基团的芳香双环结构和C_(58)H_(65)NS。②页岩可溶有机质体系模型模拟初态各族组分均一分布时能量较高,随着模拟时间推移,体系非均质性增强,能量逐步降低;饱和烃与芳香烃分子更易扩散,而非烃和沥青质具有自聚集现象,最终生成以分散小分子为主的游离子体系(饱和烃与芳香烃的总质量分数为42.9%)和以大分子聚集体为主的聚集子体系(非烃和沥青质总质量分数为74.3%);游离子体系中总分子质量更大,占原可溶有机质模拟体系总分子质量的66.7%,扩散速率更快,模拟终态时的密度更小。③分子质量和分子极性是影响纳米限域下页岩油可动性的重要因素;极性分子自聚集必然引发可溶有机质体系的非均质性变化,极性分子团簇非均匀分布并吸附在纳米孔喉空间中可造成页岩油的运移通道堵塞,从而限制页岩油的可动性。Taking the group components of medium-low maturity shale oil in the third member of Paleogene Shahejie Formation in the Bohai Bay Basin as an example,a nano-scale model of shale soluble organic matter system was constructed through molecular dynamic simulation.The molecular occurrence state of shale soluble organic matter system at the nanoscale under geological conditions was investigated.And the limiting factors of shale oil movability were analyzed.The results show that:(1)The shale soluble organic matter system model consists of four group components of saturated hydrocarbons,aromatic hydrocarbons,non-hydrocarbons,asphaltenes and water,with mass fractions of 18.6%,18.9%,19.7%,38.6%,and 4.2%,respectively.The representative molecules for each of the four group components are nC_(18),1-methylphenanthrene,the aromatic bicyclic structure with carboxylate-containing long-side-chain moieties,and C_(58)H_(65)NS,respectively.(2)In the initial state of simulation,shale soluble organic matter system shows the uniform distribution of the various components with high energy.As the simulation progresses,the heterogeneity of the system increases and the energy decreases.The saturated and aromatic hydrocarbon molecules diffuse more easily,while the non-hydrocarbons and asphaltenes exhibit self-aggregation phenomena,resulting in the generation of a free subsystem dominated by dispersed small molecules(with a total mass fraction of saturated and aromatic hydrocarbons of 42.9%)and an aggregation subsystem dominated by macromolecular aggregates(with a total mass fraction of non-hydrocarbons and asphaltenes of 74.3%).The free subsystem has a larger total molecular mass,66.7%of the total molecular mass of the original soluble organic matter simulation system,a faster diffusion rate,and a smaller density in the simulated final state.(3)Molecular mass and polarity are essential factors affecting the mobility of shale oil in the nanoconfinement.Self-aggregation of polar molecules inevitably triggers heterogeneity in the soluble organ

关 键 词：页岩油 非均质性 可溶有机质体系 分子动力学模拟 纳米限域 沥青质聚集体 分子质量 分子极性 赋存状态 

分 类 号：TE122.1[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]