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重点对伊利盆地伊宁凹陷二叠系与三叠系主要烃源岩的有机质丰度、有机质类型、有机质成熟度特征进行分析与对比。盆地二叠系主力烃源岩为铁木里克组,三叠系主力烃源岩为小泉沟群。该盆地二叠系铁木里克组烃源岩机质丰度较好,已处于成熟—高熟阶段,有利于油气的形成,是好的生油岩;盆地三叠系小泉沟群烃源岩表现为有机质丰度高,成熟度较低,生油能力较二叠系差,属于中等生油岩。二叠系铁木里克组烃源岩干酪根碳同位素δ13C介于-23.55‰~20.85‰,指示有机质母质类型为Ⅱ—Ⅲ型有机质。三叠系小泉沟群烃源岩δ13C介于-26.51‰~-20.45‰范围内,代表Ⅱ型有机质。通过镜质体反射率Ro、最高热解峰温、饱和烃轻重比、OEP值研究表明伊宁凹陷二叠系铁木里克组烃源岩有机质成熟度高,三叠系小泉沟群烃源岩成熟度相对低。总体评价认为二叠系铁木里克组烃源岩是伊犁盆地伊宁凹陷的主力烃源岩,生烃能力强,是盆地油气勘探的重点层位。
This paper mainly analyzes and compares the organic matter abundance, organic matter types and organic matter maturity of the Permian and Triassic major source rocks in the Yining Sag, Yili Basin. The main Permian source rock in the basin is Tiemurike Formation, and the main source rocks of Triassic are Junquan Gully Group. The Permian Tiemurike Formation source rocks in this basin are rich in organic matter and are in mature-high-maturity stage, which is favorable for the formation of oil and gas. It is a good source rock. The source rocks of the Triassic Xiaoquangou Group Rock is characterized by high abundance of organic matter, low maturity and poor oil generation ability compared with Permian, belonging to medium oil source rocks. The δ13C of kerogen in the Permian Tiemurike Formation source rocks ranges from -23.55 ‰ to 20.85 ‰, indicating that the parent organic matter type is organic matter type Ⅱ-Ⅲ. The δ13C of the source rocks of the Xiaoquangou Group in the Triassic range from -26.51 ‰ to -20.45 ‰, representing Type Ⅱ organic matter. The results of vitrinite reflectance Ro, peak pyrolysis peak temperature, saturated hydrocarbon light-weight ratio and OEP value show that the Permian Tiemurike Formation source rocks in the Yining Sag have high organic matter maturity, Rock maturity is relatively low. The overall evaluation suggests that the Permian Tiemurike source rock is the main hydrocarbon source rock in the Yining Depression of the Ili basin, and it has strong hydrocarbon generation ability and is the key reservoir for oil and gas exploration in the basin.