The source and sink process and its geological driving factors of shale organic matter in the Qingshankou Formation,Songliao Basin
The shale of the Qingshankou Formation in the Songliao Basin is the most important petroleum source rock in the basin.Previous studies have generally believed that the organic matter(OM)enrichment in the Qingshankou Formation is related to the formation of algal blooming and saline anoxic water environment.In this study,we discuss the biogenic sources,mineralization processes and geological drivers of organic matter in the Qingshankou Formation shale from the perspective of the source-sink process of organic matter,and synthesize the evidence from paleontology,geochemistry,petromineralogy,cyclostratigraphy and geology.We propose the following understanding:the multiple biological sources of microorganisms such as cyanobacteria and acritarches,the OM mineralization process dominated by heterogeneous iron-reducing bacteria and methanogens,and the ecological changes of the paleolake and changes in the supply of material sources driven by multiple geologic factors,such as sea intrusion and volcanoes,ultimately led to the development of primary productivity and the stratification of the water environment,resulting in the formation of a thick layer of organic-rich deposits.In the future,meticulous and systematic research of the OM enrichment mechanism of the Qingshankou Formation should be carried out,to achieve the identification and distribution prediction of the oil-rich layers of meter thickness,and to meet the needs of the shale oil exploration and development in the basin.
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