Ancient landform of the Dongying formation in the Shadongnan structural zone, western Bohai Sea area and its control on the sedimentation

The Shadongnan structural zone in the western Bohai Sea area is located in the transitional position from the Shaleitian uplift to the Sha'nan sag. Due to the influence of various factors such as inherited uplift, syn-depositional faults and ancient valleys in different periods, the development of sedimentary facies is relatively complex, restricting the further oil and gas exploration and development. We restored the ancient landform of each three-level sequence in the Dongying formation in the sedimentary period using the strata thickness method, identifying uplifts, slopes, ancient valleys, fault troughs, and shallow and deep sub-sags in the study area. Meanwhile, there are two kinds of ancient landform in the Shadongnan structural zone bounded by the NNE-trending transform fault, with the valley-paleoslope-fault slope-break in the west and the valley-multistage fault slope-break in the east. The former is composed of eroded valleys, buried hill slopes and early syn-depositional faults, while the latter er