| From the tectonic structure point of view, the collision of the two plates forms a series of orogenic belt, while in the frontal edge of the subducting plate , it is always shaped into the foreland basin. The foreland basin is convenient for the generation, migration and preservation of oil and gas, as a result, it is a favorable place for the accumulation and exploration of the oil gas.Daba Mountain, which is called the Daba Mountain arc foreland belt, is located in the central part of the central orogenic belt. It is the only parenthetical orogenic belt protruded to the south in the Qinling Trias orogenic belt.But the knowledge of the mechanism,sediment system,oil and gas generation,oil and gas reserve of Jurassic in Daba mountain foreland is still in disagreement, besides the time and the way of transformation. Daba mountain is joined north to the lower Yangtse block. Because of the breakthrough in the oil gas resource in northeastern Sichuan, close attention has been paid to the formation, evolving process of Daba Mountain in recent years ,as well as its relation with oil and gas accumulation.It is the ideal place for studying the connection between orogenic belt and the oil and gas coupling in foreland basin. Since the discovery of Puguang gas field, it is necessary to give a further insight into the generation process of the foreland basin along with its sedimentation silting history, in order to find more oil and gas filed.The research involves sequence stratigraphy in Jurassic, petroleum system in Daba mountain foreland basin in the north-east Sichuan basin etc. In this dissertation that under the theory of sequence stratigraphy, petroleum system, petroleum geology and structural geology , a major research of oil and gas accumulation of Jurassic in the researching area has been carried out ,with the allsided use of geochemical analysis . It is aim to use new theory, new method and new technology to study Jurassic literally ,systematically and quantificationally , to give an overall evaluation of the development feature about the foreland basin sequence stratigraphy, and then to predict the advantageous exploration target. Study under my tutor, I made the field investigation repeatedly in 2004, 2005 and 2006, about 110 days altogether. observed a route of 180km, measured a section of 68km, and collected about 200 pieces of sample that weighed about 300kg. The research results that based on a great number of study on the experimental analysis and statistic data as well as map, are as follows:1.Divide the sequence boundary Daba mountain foreland basin systematically for the first time. Define the symbol of distinguishing sequence boundary from outcrop through the explanation of outcrop sequence stratigraphy, the partition of sediment cycles, and the study of geochemistry. Jurassic, as an independentâ…¡order sequence, has been redivided into 7â…¢order sequence according to the structure feature such as erosion surface and the largest lake flooding surface.2.According to the analysis of features of the key outcrop sequence stratigraphy, build the sequence frame, through the section comparison, and the study of feature of the 5 key outcrops, then it can be concluded that, conglomerate on the denudation plane or the other contrastive sediment are the main features surrounding the bottom border of the sequence. In the foreland basin sediment environment, the transilient group of mud rock and sandstone are the main sediment features of low-stand system tract (LST). Thick mud rock and sandstone interbedded is the chief component of transgressive system tract (TST), sometimes together with thick turbidity current sandstone; High-stand system tract (HST) is composed by the combination of mud rock and sandstone interbedded, with the progradation as its main style. Maximum flooding surface Sediment are usually mudstone, and the thickness is different from each other.Effected by provenance from the depression northeast and the north, sandstones shaped as semicircle,are distributed in the depression northeast ,and then mudstone and silty argillite as its transition to the southwest. The sequence is classified into two types: alluvial fan-braided river sequence, which was formed by the strong tectonic movement in the lower Jurassic, lake-delta-meander river sequence that generated in the middle and upper Jurassic. These two types have been used in the particular analysis of the structure feature and the formation mechanism of the Daba mountain foreland basin sequence, and they have laid the foundation for the theoretical mode of Daba mountain foreland basin sequence stratigraphy.3.To analyze the sediment environment and paleo-climate meaning of the oxide, microelement and lanthanon of sediment and heavy minerals, create the sequence feature of geochemistry. Carry on the statistical study of sandstone crumb to distinguish the tectonic environment.4.To elaborate the history of Daba mountain foreland basin ,on the basis of the analysis of sedimentology background and the evolving feature of the structure in the researching area ,and indicate the 3 evolving stages in this process, which started in the lower Jurassic and completed in the upper Jurassic.5.According to the study of outcrop, the mud stone identified in J1 and J2 are both good hydrocarbon source rocks in the researching area, Put forward that there are 3 oil and gas accumulation systems in Jurassic of Daba mountain foreland .according to the study of outcrop, the mud stone identified in J1 and J2 are both good source rock in the researching area, Put forward that there are 3 oil and gas accumulation system in Jurassic,Daba mountain foreland. Hydrocarbon in oil and gas accumulation systems of Shaximiao formation comes from J2 or J1, Reservoir together with the source rock beneath form oil and gas accumulation system, depend on the connectivity of fault. Shale in J1 and J2 is the main source rock, they form oil and gas accumulation systems along with the overlying cap. J5 that contains a small quantity of deep water dark mud rock, may form oil and gas accumulation system with the overlying J6 channel sandstone.
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