The origin of Feixianguan reservoir bitumens in the Northeastern Sichuan Basin has been controversial for a long time.Previous knowledge mostly was based on geochemical data,and less hydrocarbon generation procedure was taken into account.In this study,basin modeling was used to investigate oil generation histories and resource potentials of three probable hydrocarbon source rocks (the Lower Cambrian,the Lower Permian and the Upper Permian mudstones) for the Feixianguan reservoir bitumens in Northeastern Sichuan basin.The results showed that the main oil generation stages occurred in the Permian-early Triassic period,early-middle Triassic period and late Triassic-early Jurassic period for the Lower Cambrian,Lower Permian and Upper Permian mud source rocks,respectively.With respect to resource potentials,the Lower Silurian mudstone source rocks produced the largest amount of oils during the whole middle-late Triassic period,accounting for 80％-90％ of the total oils generated by the three sets of source rocks.During the early Jurassic sedimentary period,the Upper Permian shale was the primary oil source rocks in the Puguang area and the Lower Silurian shale became sub-ordinary,only accounting for 10％-20％ of total oils generated during this period.However,the Lower Silurian shale source rocks contributed about 80％ of oils in the Luojiazhai area.Considering absolute oil quantities generated in the middle-late Triassic period much more than those in the early Jurassic period,the oils in Feixianguan giant paleo-pools were believed to be sourced from the Lower Silurian hydrocarbon source rock and a minor contribution from the Permian shale source rock,and its contribution is variable in different regions.It was worthy to note that the huge quantities of oils generated from the Lower Cambrian shale were not trapped in the Feixianguan paleo-pools,because their generation was prior to the formation of Feixianguan reservoirs.They might be trapped in the Paleozoic reservoir and cracked to gas during the following deep burial,which probably is one of the important targets in future exploration.%川东北地区飞仙关组锗层沥青的来源一直存在争议,以往的认识多是依据地球化学资料,而很少从生烃背景来探讨这一问题.研究应用盆地模拟方法,对川东北地区飞仙关组储层沥青三套可能的烃源岩(下寒武统、下志留统和上二叠统)进行了生油历史与潜力研究.结果表明,下寒武统、下志留统和上二叠统泥质烃源岩的主要生油期分别发生在二叠纪-早三叠世、早-中三叠世和三叠纪末期-早侏罗世.在生油潜力方面,下志留统泥质烃源岩在()个中-晚三叠世期间都具有最大的生油量,占三套烃源岩总生油量的80％～90％.在早侏罗世沉积期, 光地区油源岩以上二叠统泥质烃源岩为主,下志留统泥质烃源岩为辅,仅为总生油强度的10％～20％；而()家寨地区则以下志留统泥质烃源岩为主要油源岩,所占比例仍高达80％左右.考虑到本区中、晚三叠世期间的生油量远大于早侏罗世时期,飞仙关组古油藏原油应该主要来自下志留统泥质烃源岩,上二叠统泥质烃源岩的贡献较小,且在不同地区有所不同.本区下寒武统泥质烃源岩生油时间明显早于飞仙关储层圈闭形成期,不是该区古油藏的有效烃源岩.
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