伊宁凹陷三叠系小泉沟群沉积相分析及其生油意义

Analysis of Sedimentary Facies and Oil-Forming Significance of Xiaoquangou Group in Yining Depression in Triassic

伊宁凹陷是伊犁盆地最重要的含油气凹陷,而伊宁凹陷中上三叠统小泉沟群(T2-3XQ)又是该凹陷重要的烃源岩层段之一。为了进一步弄清楚小泉沟群生油岩的分布情况,利用钻井、测井以及二维地震资料对其沉积特征及沉积演化进行了分析和研究,识别出多种沉积相类型,主要包括湖泊相、扇三角洲相和河流相等。通过测井约束反演揭示了小泉沟群的沉积相平面展布特征,认为小泉沟群可分为上、下两段,下段主要为扇三角洲—滨浅湖相沉积,上段主要为滨浅湖—半深湖相沉积,局部发育深湖相沉积;反映了小泉沟群沉积经历了水体逐步加深、范围逐步扩大的过程。

Xiaoquangou Group is one of the important hydrocarbon source rock inte rvals in Yining Depression,the most important petroleum sag in Yili Basin.To f urther clarify the source rock distribution,the analysis of its sedimentary cha racteristics and evolution is made based on the core description,well logging a nd seismic data.Many types of sedimentary facies in the group are distinguished,mainly including lake facies,rivers facies and fan delta facies.The logging constraint inversion shows that Xiaoquangou Group can be divided into upper and lower sections.The lower segment mainly consists of fan delta-shore shallow la custrine facies deposition,and the upper one is mainly composed of shore shallo w lake-half deep lacustrine facies deposition,locally with deep lacustrine faci es.This reflects the gradual deepening and expansion of the water body of Xiaoq uangou Group.