Abstract: Wushi Sag is a half graben controlled by two master faults fault 7 and fault 6. Fault 7 dominates eastern depression with character of south dropping and north onlap. Fault 6 dominates western depression with character of north dropping and south onlap. There is a transfer zone between eastern and western depression, which accommodates hypsographic feature of two depressions. Wushi sag develops two types of overlying structure style: extension style and inversion style. Extension style is composed of the extension in Palaeocene, strong extension in Eocene, and feeble extension in Oligocene in the form of half-graben, complex half-graben, graben-horst, forward step-fault, and backward step-fault, which all are dominated by the association normal faults. Inversion style mainly occurs in center inversion zone, and it’s characteristics of east and west of center inversion zone are different. Source rock distribution, trap forming, and hydrocarbon accumulation are controlled by the tectonic activity. More hydrocarbon reservoirs found by now, which are from allochthonous source than from authigenic source, have a close relationship with the impacts of fault activity.

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