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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.
The Upper Triassic Chang 8 reservoir in the Longdong area of Ordos Basin is structurally stable and humid with a slope of only 0.1 ° and has the geological conditions for the formation of shallow water delta.By analyzing a large number of core and seismic reflection features and combining with the sedimentary characteristics of modern shallow lakes According to the comprehensive study, the water bodies in the Longdong area during the Chang 8 sedimentary period are shallower and have shallow water delta sediments, and its main sedimentary characteristics are as follows: the maturity of rock composition is low, the maturity of structure is medium, and the probability curve of grain size shows obvious traction characteristics; The delta front mouth bar and gravitational flow sedimentation is not well developed, the channel frequently diverges and reroutes and extends farther, and the sand body is larger in scale. The distribution of the shallow water delta front has a wide range of distribution and there is no obvious slope break zone with the delta plain, Not possessing the ternary structure of the Gilbert-type delta.The distributary channel sand bodies in the shallow delta front distributary channel are widely distributed and stacked in vertical and horizontal directions, which have favorable conditions for hydrocarbon accumulation and are favorable to the formation of lithologic reservoirs.