| Based on the research of development characteristics of overthrust fault, its sealing mechanism is ana- lyzed. The evaluation standard and method for sealing ability of fault is established through the following two simulation experiment: one experiment is ,the quantitative relationship between property of filler in fault zone and sealing ability of fault , another experiment is the deformation characteristics of gymsum. By evaluating sealing ability of overthrust faults on several typical structure in Kuche ression,its considered that most cur- rent faults are sealed. By growth triangle zone and profile of equilibrium technology , and the research of the formation and moving period of fracture,it's considered that formation period of fracture in different strutural zone vary greatly. The formation period of fracture is later and later from the north to the south, but the main moving period of faults is Kuche - Quaternary. The evolution history of vertical sealing ability of overthrust faults was recovered, it's considered that activity of fault exist since Jidike deposition period, but episodic. Faults are open during moving period and sealed during static period. Based on dissection of gas - bearing of typical structure in the north zone of Kuche depression, by the foundation of similarity , micro - mini physical simulation model of typical structure was established, the effect of migration and accumulation of gas through fault was simulated physically. To evaluate transporting efficiency of gas through fault, based on the analysis of factors that influence transporting ability of gas through fault an evaluation parameter was established.. By the evaluation parameter , transporting ability of gas through faults in 24 large and medium gas fields whose transporting passway is fault were studied. By the study of relation between accumulation efficiency and evalu- ation parameter of transporting ability of gas through fault, it is considered evaluation parameter of transporting ability of gas though fault of high, middle and low efficiency are separately more than 250×10-4, from 250to 25×10-4 and less than 25×10-4. According to transporting characteristics of gas through fault in the north zone of Kuche depression, transporting efficiency of gas through fault of Lower Crataceous in the region was studied. It is considered that high efficiency transporting ability places mainly distribute around well Da- bei 1, well Kela 1,2,3,4 and well Dongqou 5 - Dina 2 - Yinan 2, around of which are gas of middle and low transporting ability places. According to the difference of faults linking source rock and traps and it's combi- nation characteristics and accumulation degree of gas, four types of effect models of faults to migration and accumulation are summarized, moreover, faults model formed by subsalt fault and trans -salt fault (discon- tinuous trap) and fault models formed by trans - salt fault are the most effective models in Kuche depression, and fault models formed by subsalt fault and sudden fault on the top of trap and models formed by trans - salt fault are less effective on accumulation formation, and only can form small reservoir of gas shows. By com- prehensive analysis of generating intensity of source rock, transporting efficiency of gas through fault and thickness of caprock of Tertiary, the favorable areas of gas accumulation and distribution were forecasted. The result indicates that favorable areas of gas accumulation and distribution are around of well Dabeil, around of well Kelal ,2,3,4 and around of well Dongqou5 - Dina2 - Yinan2 in the north of Kuchen depression.
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