吴起北部长6段沉积微相特征及其对储层非均质性的影响

Characteristics of Sedimentary Microfacies of Chang 6 Member in Northern Wuqi Area and Its Effect on Reservoir Heterogeneity

为解决鄂尔多斯盆地吴起北部长6段沉积微相环境多变且储层非均质性强,加之两者之间关系复杂,导致储层有利区预测困难的问题,采用岩心观察及薄片鉴定、粒度分析、测井分析等方法对长6段的沉积微相特征进行研究,并利用统计学方法对储层的非均质性特征进行探讨。在此基础上,从河道期次、单期河道砂体厚度、河道的叠加宽度以及砂体连通性等角度分析了沉积微相与储层非均质性的关系。结果表明:湖泊三角洲前缘亚相沉积为研究区长6段的主要沉积体系类型,沉积微相类型较多,包括水下分流河道、水下天然堤、分流间湾和河口坝;单期河道的砂厚变化范围影响储层层内非均质性的强弱,河道期次与层间非均质性关系密切,而分流河道的叠加宽度以及砂体的连通性主要控制储层平面非均质性。

The sedimentary microfacies environment of Chang 6 Member in the north of Wuqi,Ordos Basin is changeable,the reservoir heterogeneity is strong,and their relationship is complex,which leads to the difficulty in predicting the favorable reservoir areas in the study area.To solve the above problems,the characteristics of sedimentary facies of Chang 6 were studied by core observation,thin section identification,grain size analysis and logging analysis.Meanwhile,the in-layer,interlayer and plane heterogeneous parameters of the reservoir were discussed by using statistical methods.On this basis,the influence of sedimentary microfacies on reservoir heterogeneity was also analyzed from multiple aspects including the frequency of channel diversion,sand body thickness of single channel,superposition width of distributary channel and connectivity of sand bodies.The results show that the Chang 6 reservoir in the study area mainly develops lake delta front sedimentation,including several sedimentary microfacies such as underwater distributary channel,distributary bay,underwater levee and mouth bar.The in-layer and interlayer heterogeneity of reservoir increases with the strength of the variation of sand body thickness in single distributary channel and the frequency of channel diversion,respectively.While the plane heterogeneity of the reservoir increases mainly with the decrease of the superposition width of distributary channel and the deterioration of the connectivity of sand bodies.