| In accordance with the questions about the exploration in Upper Triassic Foreland Basin in Western Sichuan, with the help of petroleum system and dynamics of petroleum accumulation, based on the foreland basin research achievements acquired by our predecessors, and by means of analyzing representative gas pools such as Zhongba, Pingluoba gas pools, this paper focuses on the research about dynamics of petroleum accumulation and accumulation mechanism as well as the oil and gas distribution in Upper Triassic Foreland Basin, studies the gas generation, migration, accumulation and exploration prospects in Upper Triassic Foreland Basin, systematically summarizes the outcome of the petroleum exploration in this area, and evaluates the petroleum prolific belts and the targets of exploration.The Upper Triassic Foreland Basin has the characteristics of the three fold belts from east to west and the three locks from north to south. The belts include the back mountain belt, the front mountain belt and the fore mountain belt. The blocks include the north block, the middle block and the south block. From west to east, sedimentary fades includes alluvial, delta, fluvial and lacustrine in turn. Apparently, the subsidence depocenters of the Upper Triassic Foreland Basin were different in geologic history. The to-and fro movement is northeast-southwest ward. For the foreland basin, the sedimentary thickness is very big and the stratigraphic sequences are complete. Vertically, there are three favorable source-reservoir-caprock assemblages. For the first assemblage, Xu 1 is source rock interval, Xu 2 is reservoir interval and Xu is caprock interval; for the second assemblage, Xu 3 is source rock interval, Xu 4 is reservoir interval and Xu 5 is caprock interval; For the third assemblage, Xu 5 is source rock interval, Shaximiao formation, Suiling formation and Penglaizhen formation are reservoir intervals, Cretaceous is caprock interval. For the former two assemblages, Xuejiahe formations gas reservoirs are main exploration targets and for the latter one, shallow gas reservoirs are main exploration targets.The source rocks of Upper Triassic are mainly distributed in Xu 1, Xu 3 and Xu 5, which are featured by more sequences, widespread distributions, big thickness (the total thickness of source rocks up to 350-950 m), high abundant of organic matter (TOC varying from 1.6 to 14%), strong intensity, high maturation and available to produce gas (with type III organic matter as the soul). The main reservoir intervals are distributed in Xu 2 and Xu 4. The favorable reservoir fades belts comprise channel to delta system. The reservoir facies are characterized by developed sandbody, big thickness, widespread distribution, low permeability and low porosity, high water saturation and strong heterogeneous. The pore types include residual intergranular pore, intergranular dissolved pore, intragranular dissolve pore, matrix pore and microfracture. Porous combination types include intergranular pore-intragranular pore-fracture, intragranular pore-matrix pore-fracture and matrix pores. The direct caprocks are Xu 3 and Xu 5 formations whereas the regional caprocks are Jurassic to Cretaceous red sand mudstone. These caprocks, better caprocks, are featured by big thickness, relatively stable distribution, pure argillaceous rocks, strong plasticity and high breakthrough pressure.The foreland basin is of complex structural geological conditions, various structural patterns and trap types. There are three types of traps which include structural (anticline, fault and nose-like) and nonstructural (stratigraphic and lithologic) along with compound traps in Western Sichuan. The Upper Triassic is mainly an antilcinal-fault trap whereas the Jurassic is mainly a structural-lithologic trap. The...
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