延长油区侏罗系—上三叠统层序地层与生储盖组合

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力总体特征，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。

SEQUENCE STRATIGRAPHY AND SOURCE-RESERVOIR-CAP ASSEMBLAGES OF JURASSIC-UPPER TRIASSIC IN YANCHANG OIL PROVINCE

Take the Upper Triassic regional erosion surface as sequence boundary,the Jurassic and Triassic terrigenous clastic systems in Yanchang oil province could be divided into upper sequence and lower sequence.The lower sequence (Upper Triassic)is composed of a transgressive system tract(TST)and a highstand system tract(HST).The Upper sequence (Juassic)includes a lowstand system tract(LST)overlain by a transgressive system tract(TST)and a highstand system tract(HST).Three assemblage types can be distinguished according to the disposal relationship of source reservoir cap rock assemblage:1.lithologic reservoirs,characterized by source rocks in the lower part and reservoirs in the upper part,formed during rapid subsidence with high accommodation space.The Chang 7 lacustrine facies and Chang 6 deltaic facies in the lower part of the Lower sequence are the best oil reservoir dispose;2.lithologic structural reservoirs with source rocks in the upper part and reservoirs in the lower part,and self sourced reservoirs developed in the upper part of the lower sequence represented by Chang 2 3 and Chang 1 meandering/anastomosing system. It is the second excellent oil reservoir dispose in the study area.3.structural lithologic reservoirs with source rocks in the lower part and reservoirs in the upper part associated with self sourced reservoirs developed in the upper sequence of fluvial facies(Yan 10-Yan 1 submembers).The hydrocarbon pool forming in reservoirs needs good structural trap due to poor lateral seals.