准南四棵树凹陷烃源岩评价及分布研究

Research on Evaluation and Distribution of Source Rocks in Sikeshu Sag of the Southern Junggar Basin

四棵树凹陷是准噶尔盆地南缘西段的二级构造单元,明确四棵树凹陷烃源岩潜力及分布特征,以进一步分析油气成藏机理,预测油气分布规律。通过系统分析大量钻井、地化资料,对该区中、下侏罗统与古近系安集海组(E2-3a)烃源岩进行了综合评价,并结合地震、沉积相分析、盆地模拟等方法对各烃源岩的分布进行了客观预测。研究表明,该凹陷烃源岩以湖相暗色泥岩为主,下侏罗统三工河组(J1s)暗色泥岩厚度大、有机质丰度高、类型好、热演化程度高,为该区主力烃源岩。烃源岩的平面分布明显受构造-沉积格局控制,生烃灶主要在凹陷的中部-东南部,自南向北烃源岩质量逐渐变差。

Sikeshu Sag was a secondary structure unit located in the west of southern Junggar Basin.The potential force and its distributive characters were clarified for the purpose of further analyzing its hydrocarbon accumulation mechanism and predicting its distributive rules.By systematically analyzing the drilling and geochemical data,source rocks in Anjihai Formation of the lower-middle Jurassic and Paleogene were comprehensively evaluated,combined with seismic and sedimentary facies analysis and basin modeling methods,the distribution of the source rocks was objectively predicted.Study results show that the main source rocks are lacustrine dark mudstones in the sag,dark rocks in lower Jurassic Sangonghe Formation are large thickness with high organic matter abundance,good type and a high degree of thermal evolution,they are main source rocks in the area.The distribution of source rocks is obviously controlled by tectonic-sedimentation pattern,the hydrocarbon is mainly located in the central-southeast of the sag,and its quality has been gradually poor from the south to the north.