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延长油区侏罗系和上三叠统河流湖泊三角洲相砂岩主要为长石砂岩和一部分岩屑长石砂岩及长石岩屑砂岩。具有较好的物性 ,构成良好的油气储集层。以晚三叠世抬升剥蚀造成的区域性剥蚀面为层序边界 ,可将侏罗系与上三叠统沉积体系分为两个层序 ,即上部层序 (侏罗系 )和下部层序 (上三叠统延长组 )。下部层序由一个湖进体系域和一个高水位体系域组成。上部层序从下到上依次为低水位体系域、水进体系域和高水位体系域。上下层序生储盖组合以自生自储为总体特征 ,按生、储、盖的配置关系可划分为 3种组合类型 :(1)下生上储式岩性油气藏组合 ,发育于下部层序下部 ,以长 7湖泊相长 6三角洲相为最佳油气藏配置 ;(2 )上生下储式和自生自储式岩性构造油气藏组合 ,发育于下部层序上部 ,以长 2 +3和长 1曲流河 (交织河 )水侵进积型地层为代表 ,是研究区良好的生储盖配置 ;(3)下生上储式为主、自生自储式为辅的构造岩性油气藏发育于上部层序河流相沉积体系 (延安组延 10延 1小层 )中 ,该类油气藏的形成需要较好的构造圈闭和盖层条件。
Yanchang oil-bearing deltaic sandstones in the Jurassic and Upper Triassic rivers and lakes mainly consist of feldspar sandstone and some lithic feldspathic sandstone and feldspar lithic sandstone. Has good physical properties, constitute a good oil and gas reservoirs. Taking the regional eroded surface caused by uplift and erode in Late Triassic as the boundary of sequence, the Jurassic and Upper Triassic sedimentary system can be divided into two sequences, namely, the upper sequence (Jurassic) and the lower sequence (Upper Triassic extension group). The lower sequence consists of a lacustrine system tract and a highstand system tract. The upper sequence is low-level system tract, water-derived system tract and high-water system tract from bottom to top. The upper and lower sequence reserve-reservoir-cap assemblages can be divided into three types of assemblages according to the configuration relationship of genesis, storage and cover: (1) the subsurface upper-storage lithologic reservoir assemblage developed in the lower part of the lower sequence , With the Chang 6 lacustrine facies 6 delta facies as the optimal reservoir configuration; (2) the combination of the upper and lower spontaneous storage lithologic structural reservoirs developed in the upper part of the lower sequence with length 2 +3 and length 1 The meandering river (interlaced river) water intrudes into the stratotype strata and is a good reservoir-cap configuration in the study area. (3) The development of structural lithologic reservoirs with subsistence and reservoir type supplemented by self- In the upper-sequence river facies sedimentary system (Yanchang Formation, Yanchang 10 Yan 1), the formation of such reservoirs requires good structural traps and caprock conditions.