松辽盆地梨树断陷东南斜坡白垩系主力烃源岩特征及生烃史

Characteristics and hydrocarbon generation history of the main source rocks of the Cretaceous in southeast slope of Lishu Fault Depression,Songliao Basin

松辽盆地梨树断陷主力烃源岩尚未明确。为揭示梨树断陷东南斜坡白垩系油气成藏规律,对梨树断陷东南斜坡区沙河子组、营城组泥页岩样品进行烃源岩评价和油气源对比,并且恢复烃源岩的生烃史。研究结果表明,梨树断陷东南斜坡白垩系沙河子组和营城组烃源岩有机碳含量和生烃潜力相对较好,为中等—好烃源岩。干酪根组分与生物标志物鉴定表明,东南斜坡白垩系烃源岩属于Ⅱ—Ⅲ型干酪根,为水生生物和陆生高等植物混合来源并形成于还原环境,热演化程度中等,现今仍处在生油阶段。油源对比结果表明,东南斜坡区油气均来自沙河子组烃源岩。生烃史重建结果显示,沙河子组与营城组烃源岩分别于97 Ma与94 Ma达到生烃门限,于92 Ma与89 Ma进入生烃高峰;66 Ma之后,梨树断陷整体抬升,地温梯度减小,生烃作用减弱。地球化学分析结合生烃史重构技术可以很好地用于确定多旋回叠合盆地主力烃源岩的特征,对弄清油气藏的分布规律具有重要作用。

The main source rock of the Lishu Fault Depression in the Songliao Basin has not yet been identified.In order to reveal the Cretaceous hydrocarbon accumulation law of the southeast slope of the Lishu Fault Depression in the Songliao Basin,this paper conducted the source rock evaluation and the comparison of oil and gas sources in the shale samples of the Shahezi Formation and Yingcheng Formation of the southeast slope area of the Lishu Fault Depression,and then recovers the hydrocarbon history of the source rock.The result shows that the source rocks of the Cretaceous Shahezi Formation and Yingcheng Formation of the Lishu Fault Depression have relatively good organic carbon content and hydrocarbon production potential,belonging to mediumgood source rocks.The identification of kerogen components and biomarker shows that the chalky source rocks of the southeast slope belongs to kerogen type II-Ⅲ,which is a mixed source of aquatic organisms and terrestrial higher plants and forms in a reducing environment,with a medium degree of thermal evolution,and the source rocks still in the oil-producing stage.The results of oil source comparison show that the oil and gas in the southeast slope area are all derived from the source rocks of the Shahezi Formation.The results of the reconstruction of the history of hydrocarbon production show that the source rocks of Shahezi Formation and Yingcheng Formation reached the hydrocarbon production threshold at 97 Ma and 94 Ma,respectively,and entered the peak of hydrocarbon production at 92 Ma and 89 Ma.After 66 Ma,Lishu Fault Depression was raised as a whole,and the ground temperature gradient decreased,and the hydrocarbon production effect is weakened.Geochemical analysis combined with hydrocarbon history reconstruction technology can be well used to determine the characteristics of the main source rocks in the multi-spin superposition basin,and it plays an important role in clarifying the distribution law of oil and gas reservoirs.