鄂尔多斯盆地西南部长6、长7储集层特征及控制因素

Characteristics and controlling factors of Chang 6 and Chang 7 reservoirs in southwestern Ordos Basin

为研究鄂尔多斯盆地西南部长6、长7储集层特征及其控制因素,开展了岩心观察和描述、铸体薄片鉴定、扫描电镜分析和其他分析测试工作。结果表明:①研究区可识别出垂积作用、侧向加积作用、前积作用和浊积作用等4种沉积类型,划分出水下分流河道、河口坝、重力流砂体等多种沉积微相,并识别出6种成岩相。②储层的物性由沉积作用与成岩作用共同控制,原始沉积组分较粗、塑性矿物含量低的岩石多发育绿泥石薄膜,且次生溶蚀孔隙更发育,储层物性较好;原始沉积组分较细、塑性矿物含量高的岩石,压实作用较强,硅质和碳酸盐胶结物发育,易形成致密储层。③沉积相带决定了岩石先天性的物质基础,成岩作用控制了后期岩石物性的改造效果,二者共同控制了现今岩石的储集性。该研究成果对鄂尔多斯盆地西南部有利储层预测具有指导作用。

In order to study the characteristics and controlling factors of Chang 6 and Chang 7 reservoirs in south‐western Ordos Basin,core observation and description,casting thin section identification,scanning electron mi‐croscopy analysis and other analysis and testing were carried out.The results show that:(1)Four types of sedi‐mentary facies can be identified in the study area,including vertical sedimentation,lateral sedimentation,pre-sedimentation and turbidity,and various sedimentary microfacies,such as underwater distributary channel,mouth bar,gravity flow sand body,can be distinguished,and six diagenetic facies can be identified.(2)The physical properties of reservoirs are controlled by both sedimentation and diagenesis.Chlorite films are developed in rocks with coarse original sedimentary components and low content of plastic minerals,and secondary dissolved pores are more developed,reservoir physical properties are better.Rocks with fine original sedimentary components 2 and high content of plastic minerals have strong compaction,with siliceous and carbonate developed,which are easy to form compact reservoirs.(3)Sedimentary facies zones determine the congenital material basis of rocks,and diagenesis controls the effect of later transformation of rock physical properties.Both of them control the res‐ervoir properties of present-day rocks.The results of this study can be used to guide the prediction of favorable reservoirs in southwestern Ordos Basin.