【摘要】 鄂尔多斯盆地陇东地区上三叠统长8油层组构造稳定,气候湿润,坡度仅为0.1°,具备形成浅水三角洲的地质条件.通过大量岩心观察和地震反射特征分析,并结合现代浅水湖泊沉积特征,综合研究认为,陇东地区长8沉积时期水体较浅,发育浅水三角洲沉积.其主要沉积特征为:岩石成分成熟度较低,结构成熟度中等,粒度概率曲线表现出明显的牵引流特征;三角洲前缘河口坝和重力流沉积不发育,河道频繁分叉改道,延伸较远,砂体规模较大;浅水三角洲前缘相带分布范围广,与三角洲平原之间无明显的坡折带,不具备吉尔伯特型三角洲的三元结构.浅水三角洲前缘分流河道砂体分布广泛,纵横叠置,其成藏条件优越,利于岩性油气藏的形成.更多还原

【Abstract】 The Chang 8oil-bearing interval of the Upper Triassic Yanchang Formation in the north-western Ordos Basin was de- posited in a stable tectonic setting and it was favorable in terms of geological condition for the shallow-water deltas with the hu- mid climate and the slope gradient at only 0.1°.It is found that shallow water delta was developed during Chang 8deposition by agreat number of core observations,seismic reflection characteristics analysis and modern shallow water lake sediments.It is chcharacterized with low component maturity and middle textural maturity,traction current deposits indicated by grain-size probability curves.In the study area,the mouth bar and the gravity flow deposits are not well developed,and the river has been branched off or diverted frequently due to the lake water obstruction and are widely distributed to a long distance with lar- ger scales.The delta front facies belt is characterized by its wide distribution,the gently connecting of delta plain and delta front with no obvious transition.And three-member structure of the Gilbert Delta is not developed.Therefore,the sandbodies of distributary channels are widely distributed,overlapping vertically,and extending laterally,which is favorable for the forma- tion of lithologic hydrocarbon reservoir.更多还原