| The tectonic position of Jianghan basin is in the north-central part of Yangtze Block, which is a typical inland salt lake fault basin in eastern part of China. And Jiangling depression is in the southwest of Jianghan Basin. Cretaceous-Paleogene of the Jiangling depression are terrestrial river-lakes sandstone sedimentary system. The Xingouzui group is main source rock. Zifusi sag is in the east of Jianghan Basin which located in Jiangling depression. It is rich in oil and gas resources. Commercial oil flow has shown in the Xingouzui group, Jingsha group and Qianjiang group of the Eogene system. For a long time, the oil exploration workers had different views on oil-generating capacity of Zifusi sag. Studying oil and gas migration direction, do integrated, dynamic analysis into the possession of the controlling factors and distribution law on the basis of clear hydrocarbon generation potential and hydrocarbon evolution of each source rocks, which has important practical significance to clear the exploration potential of the work area, a further evaluation of the favorable exploration targets, and guiding oil and gas exploration.This paper based on collecting predecessors’hydrocarbon source rocks results of geochemical analysis in the study area. For regional and layer which data is insufficien, appropriately complement the analysis of samples for testing in order to analyze the key horizons and key wells’crude oil physical properties and organic geochemical characteristics. Anatomy of known oil fields on the basis of analysis of the oil and gas water distribution system. Using organic geochemical characteristics of source rocks and hydrocarbon potential evaluation results, as well as crude oil geochemical data, make comprehensive comparison of multiple indicators of oil and gas source to determine the layer of oil and gas source. Combining sedimentation, tectonic evolution and hydrocarbon-generation evolution, the combination of reservoir fluid inclusion data, and dynamic analysis of oil and gas migration control factors, to clarify the hydrocarbon migration in the development of the law of the dominant channel, determine the direction of hydrocarbon migration and process, analysis of hydrocarbon migration patterns.Hydrocarbon distribution of Zifusi sag has the main following characteristics:Vertical, oil and gas is widely distributed in Xingouzui group. It is the main producing formation of Jingzhou anticline, Shashi oil field, Jingxi oil field and Zifusi sag. Oil and gas of Xingouzui group which is further divided into I, II two oil groups are mainly distributed in the lower segment. Oil and gas distributed in multi-layers, and the reservoirs scattered, the relationship between oil and water is complex, and the reservoirs are of various sizes. Plane, the oil and gas are mainly distributed in Jingzhou anticline structural belt, and Wanshi tectonic fault zone, the reservoir is more dispersed and oil blocks rarely contiguous. Every separated fault block’s oil-bearing area is small. It has many reservoir types, which fault nose oil reservoir, fault block oil reservoir and lithologic reservoir are all developed. Of all, fault nose oil reservoir is the most abundant. Wanshi tectonic fault zone is mainly based on Jingsha group and the lower section of Xingouzui group, and Jingzhou anticline structural belt is mainly based on Xingouzui group.According to the contrast of crude oil and sourcerock characteristics, the crude oil of Zifusi sag is similar to the sourcerocks of the region area and different from Meihuaiqiao area. The differences are mainly reflected in the material source and environment parameters. It indicates that the crude oil of Zifusi sag is derived from the region area.There are many factors which affect the enrichment of the oil and gas of Zifusi sag, the most important factor is the main conduit faults of the oil and gas(Such as Fuxingchang faults, etc.). Fuxingchang faults play a dual role in hydrocarbon migration which play the main channel role early, and the main closed role later. The first reason that fault closed later is tectonic activity diminished, the second is the strong mineralization along the fault plane. The thin sand which is widely distributed is also an important channel for the lateral migration of the oil and gas. Authigenic accumulation model is a model which oil accumulated spontaneously from main hydrocarbon source area and source rocks. Salt tectonics(Fuxingchang construct, Shashi construct), fault block(Fanjiatai construct, Chianjie construct, Jinjiachang construct)related to construction are developed which are mainly developed in Jingzhou anticline structural belt and Gongan monoclinic belt. The trap formed before oil and gas generation, migration and accumulation period. Reservoirs mainly to the lower segment of Shashi and Xingouzui group. The mud compartment and the large cream layer which are in the lower segment of Xingouzui group is the main cover, and they have a strong sealing ability. This accumulation model is provided with the most favorable conditions for hydrocarbon source. |
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