Abstract: There is great exploration and development potential of shale oil in Qingshankou Formation in the north of Songliao Basin, but its sedimentary cycle framework and organic matter enrichment response model are still unclear. Based on wavelet transform analysis and spectral analysis of the natural gamma logging data of Qingshankou Formation in Well Guye1, in combination with analysis results of the core, logging data and geochemical elements, the paper identifies the Milankovich cycle in the sedimentary strata, establishes the relationship between the theoretical orbital period and the single-well sedimentary cycle, and achieves the identification and division of the high-precision sedimentary cycles of Qingshankou Formation in Songliao Basin. The floating astronomical timescale of Qingshankou Formation is established according to the long eccentricity period of 400 ka. The sedimentary time of Qingshankou Formation is calculated to be 5.6 Ma. The organic-rich mud shale of Member 1 of Qingshankou Formation deposits during Late Cenomanian to Early Turonian of the Late Cretaceous. The Milankovitch cycle of Qingshankou Formation can be divided into 14 long eccentricity cycles and 46 short eccentricity cycles. The long and short eccentricity cycles correspond to the fourth and fifth levels of sequence stratigraphy respectively. On this basis, the sequence stratigraphic framework of astronomical cycles can be built in the study area, thus providing an idea for the unified stratigraphic division of deep and shallow water areas. Based on the established sedimentary model controlled by the long eccentricity cycle, it is found that when the eccentricity is close to the maximum, the corresponding sedimentary cycle will be in the organic-rich interval, which is the potential high-quality interval for shale oil exploration.

Key words: Songliao Basin, Qingshankou Formation, Milankovich cycle, high-frequency sequence, organic matter enrichment

摘要： 松辽盆地北部青山口组页岩油的勘探开发潜力巨大,但目前对其沉积旋回格架及有机质富集响应模式认识不清。对古页1井青山口组的自然伽马测井数据分段开展小波变换分析和频谱分析,并综合岩心、测井资料和地球化学元素分析成果,识别出蕴含在该套沉积地层中的米兰科维奇旋回,建立了理论轨道周期与单井沉积旋回的联系,实现了松辽盆地青山口组高精度沉积旋回的识别与划分。依据400 ka的长偏心率周期建立了青山口组的"浮动"天文年代标尺,计算出青山口组的沉积时间在5.6 Ma,青山口组一段富有机质泥页岩为晚白垩世Cenomanian晚期—Turonian早期的产物。青山口组的米兰科维奇旋回可划分为14个长偏心率旋回和46个短偏心率旋回,长、短偏心率旋回分别对应层序地层学的四级、五级层序,由此可搭建研究区天文旋回层序地层格架,为深、浅水区的统一地层划分提供思路。基于建立的受控于长偏心率旋回的有机质沉积响应模式发现,偏心率接近极大值时对应沉积旋回为富有机质层段,该层段是页岩油勘探的潜在优质层段。

关键词: 松辽盆地, 青山口组, 米兰科维奇旋回, 高频层序, 有机质富集