摘要： 油气勘探开发实践表明，从“源外”向“源内”转变是石油工业持续发展的必然选择。近来，在松辽盆地北部青山口组半深湖—深湖相纯页岩型泥页岩中获得非常规油气突破，证实了其广阔的资源前景。沉积古环境对有机质富集、沉积相分布及岩相发育具有显著的控制作用。因此，开展泥页岩地层的古环境重建研究，对非常规储层“甜点区”的精准预测具有重要的理论指导意义。本文通过生物标志化合物、元素地球化学等实验方法，对松辽盆地北部湖盆古气候、古盐度、古氧化还原条件、陆源碎屑输入、古生产力等参数进行恢复，明确了青山口组形成时期的古气候演化特征，并与国内其他主要页岩油气资源富集盆地古环境进行对比。结果显示，青山口组样品生物标志化合物正构烷烃以单峰为主，样品多以nC₁₈、nC₁₉、nC₂₀和nC₂₁为主峰碳，姥鲛烷/植烷比值为0.44~1.31，平均值为0.87，整体来看具有植烷优势；主量元素中CaO、Na₂O和P₂O₅相对富集，微量元素中Sr元素富集程度最高，Ba、V、Cr、Ni、Cu、Rb、Y几种元素相对亏损。研究结果表明：松辽盆地整体发育在炎热潮湿的古气候条件，其中古龙凹陷相较于三肇凹陷更为潮湿，青一段底部相较于中、上段更具炎热潮湿的特征；受来自东侧的古太平洋海侵影响，湖盆水体盐度较高，其中东侧的三肇凹陷水体咸化程度更高；松辽盆地北部青山口组沉积时期古生产力水平整体较高，盆地整体表现为贫氧—缺氧的还原环境，为有机质的富集和保存提供了良好的基础。

关键词: 松辽盆地, 古龙凹陷, 青山口组, 古环境, 泥页岩

Abstract:

The practice of oil and gas exploration and development shows that the transformation from “outside source” to “inside source” is an inevitable choice for the sustainable development of petroleum industry. Recently, the breakthrough of unconventional oil and gas in semi-deep lacustrine facies shale in the Qingshankou Formation (K₂qn) in the northern Songliao Basin has proved that it has broad resource prospects. The sedimentary paleoenvironment controls the accumulation of organic matter and the distribution of lithofacies, which is the basis for the prediction of shale oil desserts. In this paper, by means of experimental methods of biomarkers and element geochemistry, parameters such as paleoproductivity, paleoreoxidation, and paleosalinity of the lake basin in the northern Songliao Basin were recovered to clarify the paleoclimate evolution characteristics during the formation of Qingshankou Formation, and to compare the paleoenvironment with that of other major shale oil and gas resource enrichment basins in China. The biomarker compounds in the Qingshankou Formation samples predominantly exhibit a unimodal distribution of n-alkanes, with major peaks at nC₁₈, nC₁₉, nC₂₀, and nC₂₁. The Pr/Ph ratio ranges from 0.44 to 1.31, with an average value of 0.87, indicating a general dominance of phytane. Among the major elements, CaO, Na₂O, and P₂O₅ are relatively enriched, while among trace elements, Sr shows the highest enrichment, with Ba, V, Cr, Ni, Cu, Rb, and Y being relatively depleted. The research results indicate that the Songliao Basin developed under warm and humid paleoclimate conditions. Among the sub-basins, the Gulong Sag was relatively more humid compared to the Sanzhao Sag. The lower section of the Qingshankou Formation exhibited warmer and more humid characteristics compared to the middle and upper sections. Influenced by the transgression of the Paleo-Pacific Ocean from the east, the salinity of the lake basin water was relatively high, with a higher degree of salinization observed in the eastern Sanzhao Sag. During the depositional period of the Qingshankou Formation in the northern Songliao Basin, overall paleoproductivity levels were high. The basin predominantly exhibited a dysoxic to anoxic reducing environment, which provided favorable conditions for the accumulation and preservation of organic matter.

Key words: Songliao Basin, Gulong Sag, Qingshankou Formation, paleoenvironment, mud shale

中图分类号: 

• P618.13

• TE12