Abstract: In order to clarify the relationship between characteristics of the fault network system and oil-gas distribution in a petroleum basin, fault systems of each layer were analyzed from a case study of the western area of Wenchang A sag in ZhuIII Depression. The topological structures and fractal characterristics of the fault network system were quantitatively characterized, and their relationship with hydrocarbon distribution was discussed based on the analysis of nodes and branch types and the calculation of fractal dimensions. The results show that faults, which primarily changed from NE to NWW, are controlled by the clockwise transformation of regional stress. The topological structures of each horizon are different, with the topological values near the ZhuIII south fault, ZhuIII 6 fault and ZhuIII 2 fault being higher. The proportion of I nodes in the deep to shallow gradually increases, while the proportion of Y and X nodes gradually decreases. Meanwhile, the proportion of I-I branches gradually increases, and the proportion of I-C and C-C branches gradually decreases. The fractal characteristics from different layers vary. The fractal dimensions of the intersection of the NE fault zone and the NW fault zone are higher, and the fractal dimensions from deep to shallow increased initially and then decreased. Combined with the analysis of Wenchang A sag, we conclude that topological structures and fractal characteristics of the fault systems have a well-coupled relationship with hydrocarbon distribution. Therefore, the overlapping zones of higher topological values and the higher fractal dimensions are favorable development areas f or hydrocarbon reservoirs.

Key words: fault network system, topological characteristics, fractal characteristics, fault network connectivity, hydrocarbon
accumulation, Wenchang A sag