伊犁盆地尼勒克凹陷烃源岩有机地球化学特征及生烃潜力分析

摘要

The Carboniferous,Permian and Jurassic hydrocarbon rocks are distributed extensively in various subordinate depressions in Yili basin.However,the investigation on organic geochemistry and hydrocarbon generation potential of those source rocks is mainly focused in the Yili depression,and subordinately in Nileke depression.Based on the previous study and organic geochemical analysis,this paper reports the organic geochemistry and hydrocarbon generation potential of the Carboniferous,Permian and Jurassic source rocks in the Nileke depression.The results as follow:(1) The TOC in source rocks show a decreasing tendency from the Permian Tamuqisayi Formation (Good),to Jurassic (FairGood),Carboniferous Akesake Formation (Poor-Fair) and Permian Xiaoshansayi Formation (Poor),with the carbonate rocks preserved within Akasake Formation being none-hydrocarbon source rocks;(2) The kerogen type in various source rocks from varing geological ages are represented by type-Ⅱ to type-Ⅲ kerogen;(3) Thethermal maturity of organic matter displays a decreasing tendency from Carboniferous (post-mature stage) to Permian Xiaoshansayi Formation (high mature) and Tamuqisayi Formation (low-mature to mature) and Jurassic (none-mature to.low-mature).The high thermal maturity in Carboniferous may be attributed to development and evolution of rift valley.The middle-upper sections of Tamuqisayi Formation are considered as excellent hydrocarbon source rocks.%伊犁盆地石炭系、二叠系和侏罗系烃源岩广泛分布于各次级凹陷,但烃源岩有机地球化学特征和生烃潜力的研究主要集中于伊宁凹陷,尼勒克凹陷烃源岩的研究较薄弱,为此,在结合前人研究基础上,通过有机地球化学分析技术,综合评价尼勒克凹陷石炭系、二叠系和侏罗系烃源岩的有机地球化学特征和生烃潜力.结果表明:①有机质丰度自二叠系塔姆其萨依组(好)-侏罗系(中等-好)—石炭系阿克萨克组泥岩(差-中等)—二叠系晓山萨依组(非烃源岩-差)依次降低,其中阿克萨克组碳酸盐岩段为非烃源岩层段;②不同时代烃源岩有机质类型主要以Ⅱ2-Ⅲ型为主;③有机质热演化程度自石炭系(过成熟)、二叠系晓山萨依组(高成熟)、塔姆其萨依组(低成熟-成熟)和侏罗系(未成熟-低成熟)依次降低,其中石炭系高的热演化熟度可能与裂谷的发育和演化有关.分析认为二叠系塔姆其萨依组中上段为优质烃源岩层段.