| The object of this paper is Chang9oil formation of Yanchang Formation in Zhijing-Ansai area, Ordos basin. By using advanced theories of sedimentary, geophysics, geochemistry and sedimentary basin analysis, combining with outcrops, drilling and logging data, the source directions, microfacies types and characters, sand body plane and spatial distribution rules are deeply researched. Then sedimentary pattern is established and the influence factors of sedimentary systems over oil reservoir are discussed.The research provides certain foundation for the further oil exploration.The total thickness of Chang9oil formation of Yanchang Formation in Zhijing-Ansai area is about71.8-120m.From top to botoom, the strata is divided into upper and lower layers, and each layer thickness changed little and stable.The sedimentary source was mainly from northeast and southwest.Among them, the major provenance was northeast. The source rocks of the northeast proveniences were the Archaean high grade metamorphic rock which came from Daqing and Yin mountains, north rim of the basin.Controlled by source directions, the northeast and sourthwest sedimentary systems were developed. The dalta front deposition was mainly distributed, and the shallow lake facies was developed in central of study area. Based on outcrops and core observations, logging data, geochemistry characters, combining with single well sedimentary facies analysis, the conclued was made. The dalta front deposition and the shallow lake deposition was mainly distributed in study area. The distribution pattern of sand bodies, extending form northeast to southwest, was controlled by sedimentary facies. The scope of the shallow lake in Wucangbu-Wuqi-Zhangqu-Zhidan-Zhuanyaowan area, trumpet-shaped opening to the southeast.Oil reservoirs were controlled by sedimentary facies, the hydrocarbon source rocks in the top of Chang9oil formation which called "Lijiapan shale" supplied the reservoir-forming with the high quality source rocks. |
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