Research On Hydrocarbon Enrichment Rules Of Gentle Slop In Half Graben Basin

In JiZhong depression, Slope region is the most important prolific zone for oil and gas accumulation. And LiXian slope, which is located in the west of RaoYang sag that is full of oil and gas resources, is very rich in Oil and gas resources and has great potential for exploration. However, it had since faced many practical problems, such as the variety of depositional systems, the lamina sand body, the fast lateral variation in reservoir, the complexity of oil-water contact relationship, and the confusion of hydrocarbon accumulation mechanism and law of oil and gas distribution. Therefore, the systematic research, including the basic characteristics of various accumulation elements and the key factor that controlled the hydrocarbon accumulation, had been carried out. The establishment of hydrocarbon accumulation model and the summarization of oil and gas accumulation law had been done. These researches are of great theoretical and practical significance for exploration and development in LiXian slope as well as other similar slopes.Based on core, well drilling, geochemistry and seismic data, guided by new concept and latest technology of Reservoir sedimentology, Geology of petroleum and Geophysics, following the ideas and methods of combining micro with macro, the local with the overall and static with dynamic ,the study of static and dynamic accumulation elements, such as structure, reservoir, oil sources and migration from the upper of the third member of the Shahejie formation to the lower of the first member of the Shahejie formation, had been carried out in the paper. Focusing on analyzing the different affection of various controlling factors of hydrocarbon accumulation and hydrocarbon distribution, the effective model of hydrocarbon accumulation had been established and also the law and controlling factors of oil and gas enrichment had been clarified. Finally, the favorable zones for rolling exploration and development had been predicted and evaluated. Meanwhile, the key reservoir was selected to be finely characterized. Through the studies that mentioned above, the following essential awareness and conclusions had been made in this dissertation:1. The type of slope was the macro-factor that controlled the distribution of oil and gas. While faults and structural noses were the main structures that affected the hydrocarbon accumulation in LiXian slope. Three fault types in three chrons developed in Li Xian slope, in which, the northeast strike and continuous active ones which started early and ended later were the most important reservoir-forming faults that controlled the formation of structural nose traps and patterns of hydrocarbon charging. Affected by basal paleohigh and post tectonic movement, the structural nose, which had experienced different phases of formation and evolution, had a significant role in controlling the development of trap, the distribution of sand body, the hydrocarbon migration and accumulation.2. Different intensity of Sediment supply and different type of slopes were the core reasons that caused the different sedimentary sequence filling patterns between the North and the South in Paleogene. The prevalent sedimentary facies of the north were braided river delta and banks or bars of shore and shallow lake deposition, while those of the south were braided river and braided river delta.3. The main source rock in LiXian slope was the“special lithology”of the lower of the first member of the Shahejie formation, which began to generate greatly at about 10-6Ma and to be largely expulsion at about 8-4Ma in the middle and late term of Minghuazhen formation deposited. The abnormal high pressure, generated by hydrocarbon generation, was the driving forces for expulsion. And four types of expulsion models, determined by different lithological association, confined the layers of oil and gas enrichment. Nevertheless, the secondary migration had its own macro-characteristics: the priority of lateral migration, the nearer the better for hydrocarbon accumulation, the overall migratory direction pointed to the slope and the sand body acted as the migration pathway.4. Five typical regional hydrocarbon accumulation models had developed in LiXian slope, within which, the conjunction of source rock and reservoir caused by consequent fault was the most meaningful model for hydrocarbon accumulation in the deep formation of the north. Meanwhile, the“four stages and five elements”mode that controlled the hydrocarbon accumulation in slope zone had been proposed, which was a type that slope controlled the accumulation areas, the second order structure zone controlled the accumulation belt, the oil sources and the oil charging mode controlled the accumulation formation, the distribution of sand body controlled the accumulation boundary.5. The ChuAn structural nose in the north and the ZhaoHuangZhuang structural nose in the south are the favorable areas for further rolling exploration. At the same time, on the basis of finely characterizing of the Gao43 district reservoir in XiLiu10 fault block, the reasons causing the complexity of oil-water contact had been obtained, which were the poor physical property of the reservoir, the low range of structure and the wrong correlation of sand body. Through the fine characterizing, the main favorable places for prospecting had been predicted, which are located along the direction of channel extension (the downdip direction of south-east).Through comprehensive and integrated studies, the obtained results and awareness have got apparent effectiveness in actual rolling exploration and development. It has a great significance in guiding the rolling exploration in LiXian slope to a new era.