Abstract: Oil and gas shows are enriched in Qungkurqack structural belt on Mageti slope in southwest depression of Tarim basin, but multi-resource rocks, multi-stage hydrocarbon generation and tectonic activities allow its hydrocarbon accumulation period still difficult to study. This paper reveals its hydrocarbon accumulation stages and hydrothermal fluid flowing history based on the geochemical characteristics of fluid inclusions integrated with the numerical simulation of deposit-buried history, paleo-geothermal history. Microscope observation shows that the zone with hydrocarbon fluid inclusion from Well Qun-4 in this structural belt is corresponding to oil-bearing layers; hydrocarbon fluid inclusions are found in limestone of Xiaohaizi formation and sandstone of Silurian formation in Well Jia-1, with relatively low abundance of oil, indicating hydrocarbon migration happened here, but not forming petroleum accumulation. These fluid inclusions can be classified into two types: one is of low homogeneous temperature characterized by light blue fluorescence, the other is of high homogeneous temperature by yellow fluorescence in terms of homogeneous temperature and fluorescence features. It is concluded that two hydrocarbon accumulation stages occurred in this belt, one in Late Permian, with possible Cambrian-Ordovician source rocks and high maturity; the other in Neogene, with possible Carboniferous source rock and low maturity. Also, the homogeneous temperature of aqueous inclusion displays that Well Jia-1 and Well Ba-4 in Selibuya fault belt are higher than the geothermal value at the same depth in this area, showing that normal abnormity of geothermal fluid exists in this fault belt, which could be formed by deep high geothermal fluid migrating to shallow strata along the fault belt.

Key words: Tarim basin, inclusion, hydrocarbon migration, hydrocarbon accumulation, geochemistry