Topological structure, fractal characteristic of fault network system and their relationship with hydrocarbon migration：Taking Wenchang 9/8 area in the Pearl River Mouth Basin as an example

Abstract: To clarify the relationship between the complexity of the fault network systems and hydrocarbon migration in petroleum basin, 3D seismic data and hydrocarbon migration data from T50, T60 and T70 horizon in Wenchang 9/8 area were analyzed. The complexity and connectivity of the fault network system at different horizons in Wenchang 9/8 area are quantitatively characterized based on the topology and fractal theory. The relationship between the distribution characteristics of the complexity of the fault network system and hydrocarbon migration at different horizons in Wenchang 9/8 area was revealed combined with hydrocarbon migration data in typical zones. It indicates that the fractal dimension high value areas, and the topological high value areas and hydrocarbon migration area shave a good coupling relationship in the fault network system. The results showed that: there has a good coupling relationship among the fault interaction zone (fracture tip, structural transition zone, etc.), the fractal dimension high value areas and the topological high value areas. The peak values of the number of nodes (Nc) in T50, T60 and T70 horizons are in the range of 1-2, 6-8 and 5-7, respectively. The peak values of the fractal dimension (D) in T50, T60 and T70 horizon are among 1.4-1.6, 1.6-1.8 and 1.5-1.8, respectively. There is a good coupling relationship between fault interaction zone and hydrocarbon migration zone. Comparing with other structural area, the fault interaction zone has higher topological value and fractal dimension value. The topological high value area has good connectivity, and the fractal high value area has more faults, which is conducive to the formation of fault traps. Therefore, the overlapping zone with high topological value and high fractal dimension value are the dominant channels for oil and gas migration, which are favorable for the formation of favorable oil and gas reservoirs.