鄂尔多斯盆地镇泾地区长8段储层非均质性及其结构模式

鄂尔多斯盆地南部镇泾探区的主力含油层段为上三叠统延长组长8段，油藏类型为典型的三角洲前缘分流河道砂岩岩性油藏，储层致密低渗，非均质性强，含油饱和度变化大，开展储层非均质性研究对认识储层内部结构、形成机制和甜点预测均具有重要意义。通过对长8段致密砂岩储层不同尺度的观察和采样测试，分析了储层层内非均质性特征及其成因机制，建立了致密砂岩储层结构型非均质模型。结果表明:镇泾地区延长组长8段致密砂岩储层的非均质性极强，表现为多期河道砂体的削蚀截切和无序叠置，即使在同一厚层块状砂体内，物性和含油性也存在较大差异。细粒沉积隔夹层、富软岩屑砂岩和钙质致密胶结砂岩在空间上的配置关系决定了碎屑岩储层的非均质性。不同期次河道的彼此改造、不同类型砂岩的差异成岩演化和石油的选择性充注，造成了延长组长8段砂岩储层的结构型非均质性及其含油性差异。

Heterogeneity and Structural Pattern of Chang 8 Reservoir in Zhenjing Area,Ordos Basin

The Chang 8 member of the Upper Triassic Yanchang Formation is the main oil layer in the Zhenjing area in the southern Ordos Basin. The reservoir rock of the Chang 8 member is mainly typical distributary channel sandstone in a delta front， of lithological reservoir type. The reservoir is dense and low?permeability， with strong heterogeneity， and it shows major changes in oil saturation. The study of reservoir heterogeneity is of great significance for understanding the internal structure and formation mechanism and for the prediction of sweet points in the reservoir. The degree of heterogeneity and genetic mechanism of the reservoir were analyzed， and a model of the structural heterogeneity of a tight sandstone reservoir was established. The results indicate very marked heterogeneity in the Chang 8 member reservoir， showing erosion and disorderly overlapping of the channel sandbodies over multiple periods. Even within the same thick， massive sandbody， there are considerable differences in physical and oil?bearing properties. The heterogeneity of a clastic reservoir is a result of the spatial distribution of fine?grained sedimentary interlayering， soft lithic sandstone and calcareous tightly cemented sandstone. These properties are due to the changes in different sand channels at different times， the differential diagenetic evolution of different types sandstones and selective filling of oil.