Genetic mechanism and oil-controlling effect of curved faults in rift basins: A case study of the Bohai Sea area basins

ObjectiveThere are numerous and widely distributed curved faults in the Bohai Sea, which control the development of structural traps. However, for a long time, the genetic mechanism of curved faults has not been systematically sorted out, and their impact on hydrocarbon accumulation has not been clarified, which restricts hydrocarbon exploration. MethodsBased on 3D seismic data, fault displacement analysis, finite element stress simulation, and other methods, an in-depth study was conducted on the development mechanism and reservoir-controlling characteristics of the curved faults in the Bohai Sea. ResultsThe results showed that the curved faults mainly included four types: lateral traction type, strike-connected type, oblique extensional type, and strike-slip rotating type. The lateral traction type had the largest fault displacement on the top of the arc, the oblique extensional type had the smallest fault displacement on the top of the arc, whereas the strike-connected type had the smallest fault displacement on the flank of the arc top. The large differential stress at the top of the curved faults promoted the development of microfractures and improved reservoir quality. The curved faults were usually self-migration and self-sealing faults, and the self-migration and self-sealing ability was related to the dip angle of the foot-wall strata of normal faults, the angle between the structural trap contours and the curved faults, and the curvature of the curved faults. The stronger the self-migration and self-sealing ability of the curved faults, the easier it was to form reservoirs. ConclusionThis study clarifies the development mechanism of the curved faults in the Bohai Sea and their impact on hydrocarbon accumulation, providing important guidance for hydrocarbon exploration.