以准噶尔盆地玛湖凹陷下二叠统风城组页岩为例,综合岩心观察、测试分析、地质剖析和数值模拟等方法,识别页岩层系石油微运移现象,采用自主研发的排烃潜力法定量评价页岩油微运移烃量并进行了可靠性验证,指出页岩油微运移评价的石油地质意义.研究表明:页岩层系富有机质纹层和贫有机质纹层之间存在明显的页岩油微运移,富有机质纹层生烃能力强,生成烃类的重质组分优先与干酪根溶胀或吸附滞留,轻组分以游离态运移到与其互层的长英质或碳酸盐贫有机质纹层富集;玛页1井风城组69%的页岩存在外来运移烃的充注,31%的页岩发生了排烃作用.综合基于地质色层效应的族组分、二维核磁共振以及无机锰元素在烃类运移过程中的地球化学行为等分析,验证了微运移评价结果的可靠性;微运移是连接页岩层系各个油气聚集要素的桥梁,贯穿页岩油从生成、排出到富集的全过程,影响页岩油的含量和组分.页岩油微运移识别与评价结果,将为揭示页岩油动态差异富集机制、建立页岩"多级生油高峰"模式提供新视角.
Taking the Lower Permian Fengcheng Formation shale in Mahu Sag of Junggar Basin as an example,core observation,test analysis,geological analysis and numerical simulation were applied to identify the shale oil micro-migration phenomenon.The hydrocarbon micro-migration in shale oil was quantitatively evaluated and verified by a self-created hydrocarbon expulsion potential method,and the petroleum geological significance of shale oil micro-migration evaluation was determined.Results show that significant micro-migration can be recognized between the organic-rich lamina and organic-poor lamina.The organic-rich lamina has strong hydrocarbon generation ability.The heavy components of hydrocarbon preferentially retained by kerogen swelling or adsorption,while the light components of hydrocarbon were migrated and accumulated to the interbedded felsic or carbonate organic-poor laminae as free oil.69%of the Fengcheng Formation shale samples in Well MY1 exhibit hydrocarbon charging phenomenon,while 31%of those exhibit hydrocarbon expulsion phenomenon.The reliability of the micro-migration evaluation results was verified by combining the group components based on the geochromatography effect,two-dimension nuclear magnetic resonance analysis,and the geochemical behavior of inorganic manganese elements in the process of hydrocarbon migration.Micro-migration is a bridge connecting the hydrocarbon accumulation elements in shale formations,which reflects the whole process of shale oil generation,expulsion and accumulation,and controls the content and composition of shale oil.The identification and evaluation of shale oil micro-migration will provide new perspectives for dynamically differential enrichment mechanism of shale oil and establishing a"multi-peak model in oil generation"of shale.