摘要
为了明确源内页岩油差异富集机制,以鄂尔多斯盆地三叠系延长组7段3亚段(简称长7_(3)亚段)为例,通过高分辨率扫描电镜-光镜-激光拉曼光谱技术、岩石热解以及有机溶剂抽提实验等多种方法联合,识别不同成因固体沥青,以获取页岩油源内微运移直观证据,并建立页岩微纳米组构与石油生成、运移和富集的耦合关系。研究发现:长7_(3)亚段页岩纹层富含藻类体,其生烃潜力最高但热转化程度较低,且微米级黏土质与长英质条纹的频繁交替导致内部排烃效率高,原位和运移固体沥青芳香度相似;泥岩纹层富含陆源有机质和黏土矿物,其生烃门限较低且滞留烃类的能力更强,内部保留一定量的轻质油或沥青,使得原位与运移沥青化学结构具有明显分异;凝灰质及砂质纹层富含长英质矿物和运移沥青,前者在页岩生烃增压下形成高角度微裂缝,提高了原油向砂质层刚性矿物粒间孔充注的能力。在运移分馏作用下,页岩纹层、凝灰质纹层、泥岩纹层和砂质纹层固体沥青的有机碳芳构化程度依次降低,原油轻质组分含量依次增加,因而有机质孔发育程度依次提升。长7_(3)亚段页岩油源内运移和富集受有机-无机成岩综合作用,原油组分分馏是形成“纹层型”页岩油甜点段的重要机制。
To clarify the mechanism of differential enrichment of intrasource shale oil,taking the third of seventh member of the Triassic Yanchang Formation(Chang7_(3) submember for short)in the Ordos Basin as an example,we integrated high-resolution scanning electron microscopy(SEM),optical microscopy,laser Raman spectroscopy,rock pyrolysis,and organic solvent extraction experiments to identify solid bitumen of varying origins,obtain direct evidence of intrasource micro-migration of shale oil,and establish the coupling between the shale nano/micro-fabric and the oil generation,migration and accumulation.The Chang7_(3) shale with rich alginite in laminae has the highest hydrocarbon generation potential but a low thermal transformation ratio.Frequent alternations of micron-scale argillaceous-felsic laminae enhance the hydrocarbon expulsion efficiency,yielding consistent aromaticity between in-situ and migrated solid bitumen.Mudstone laminae rich in terrestrial organic matter(OM)and clay minerals exhibit lower hydrocarbon generation threshold but stronger hydrocarbon retention capacity,with a certain amount of light oil/bitumen preserved to differentiate the chemical structure of in-situ versus migrated bitumen.Tuffaceous and sandy laminae contain abundant felsic minerals and migrated bitumen.Tuffaceous laminae develop high-angle microfractures under shale overpressure,facilitating oil charging into rigid mineral intergranular pores of sandy laminae.Fractionation during micro-migration progressively decreases the aromatization of solid bitumen from shale,through tuffaceous and mudstone,to sandy laminae,while increasing light hydrocarbon components and enhancing OM-hosted pore development.The intrasource micro-migration and enrichment of the Chang7_(3) shale oil result from synergistic organic-inorganic diagenesis,with crude oil component fractionation being a key mechanism for forming sweet spots in laminated shale oil reservoirs.
作者
王莹珠
侯雨庭
杨继进
WANG Yingzhu;HOU Yuting;YANG Jijin(Key Laboratory of Deep Petroleum Intelligent Exploration and Development,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;PetroChina Changqing Oilfield Company,Xi’an 710018)
出处
《石油勘探与开发》
北大核心
2025年第5期1104-1117,共14页
Petroleum Exploration and Development
基金
国家科技重大专项(2024ZD1404901,2025ZD1404106)
中国科学院战略性先导科技专项(B类)(XDB10050100)。
