| Based on the research of structure and sedimentary background in working area, 12 faults (WU39, WU76, WU21, WU80, WU90, WU82, WU16, WU54, Bayantala, WW34, WW33 and WW51) in Wuerxun depression were selected for the research. The research on the development and distribution of these 12 faults were done by the change of fault distance strire distance, horicon faulted and dip angle based on seismic cross section and structure map, and the zonal distribution of faults had gotten. There are three main fault zones in the north of Wuerxun depression, south-north Wurennuoer, north-east Tongbomiao and north-east-east Wuxi fault zones, and there are three main fault zones in the south of Wuerxun depression, north-north-east Bayantala, nearly south-north middle and north-west middle-east fault zones. The two sets of fault systems are separated by T22 fault on cross section, upper and lower fault systerms, and the upper fault system developed on the lower fault system which controlled the upper fault system. The research on evolution history of these 12 faults in Wuerxun depression were done based on structure evolution, and the fault active period had been gotten in the north and south of Wuerxun depression, the first fault active period was from early k1t to end of k1n2 and the second fault active period was early k1y to early k2q in the north of Wuerxun depression, and the first fault active period was from early k1t to end of k1d1 and the second fault active period was k1y1 to early k2q in the south of Wuerxun depression. By using seepage experiment of oil-gas through fault zone and plastic deformation experiment of mudstone, the evaluation standards of fault seal were quantitatively determined, that's fault can seal oil vertically when the pressure on fault plane reaches 5MPa and mud content in fault zone reaches 50%, while the fault can seal gas vertically when the pressure on fault plane is more than 5MPa and mud content in fault zone reaches 81%. Based on these evaluation standards, the research on period and space distribution and evolution of vertical seal for oil and gas of 12 faults in Wuerxun depression was done and the faults in k1d1 and k1d2 and k1n2 have good vertical oil-gasseal in Wuerxun depression with northern being better than southern. On vertical the faults in k1d1 and k1d2 and k1n2 have good vertical seal in Wuerxun depression with other Stages being poorer, while laterally, east of the faults (WU 76, WU90, WU82, WU54, WU16, WW33, WW34 and WU39) and south of WU80 have good vertical seal with others poorer. From development history of faults, most of the vertical seal of faults in the north of Wuerxun depression were formed at early k2q, while the vertical seal of faults in south of Wuerxun depression were formed at early k1d or at early k1y.seal gradually increases and suitbale for oil-gas to accumulate and storage. From relationship between the distribution and period evolution of faults seal and the oil-gas distribution and expulsion hydrocarbon history of source rock, it is the faults in Wuerxun depression that play an important role in controlling formation of oil-gas reservoirs and oil-gas distribution, that's the fault active period was just the time for oil-gas to migrate. The good seal in k1d1 made oil-gas to accumulate in k1n2, and so the better matching relationship between the seal period of faults and main expulsion hydrocarbon period of source rock is good for large scale of oil-gas to accumulate. It is favorable for oil-gas to accumulate near faults uhich strike direction is NNE and NEE direction and fault distance is less than 100.
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