Control of tectonic-paleogeomorphology on deposition: A case from the Shahejie Formation Sha 3 member, Laizhouwan Sag, southern Bohai Sea

Based on seismic and logging data, the characteristics of tectonic-paleogeomorphology of the Laizhouwan sag during the sedimentation of the Paleogene Shahejie Formation Sha 3 member (E2s3) were restored and the control of tectonic-paleogeomorphology on sedimentary systems was analyzed. During the sedimentation of E2s3, the Laizhouwan sag can be divided into eight tectonic units, including the eastern fault-slope zone, northeastern slope, northern slope zone, western slope zone, southern slope zone, central uplift belt, northern sub-sag and southern sub-sag; gullies occur in the western and southern slope zones. Controlled by the tectonic-paleogeomorphology, the fan delta was developed in the eastern Laizhouwan sag and the braided river delta was formed in the south and west of the Laizhouwan sag in the sedimentary period of E2s3, and the developmental place of the main part of the deltaic depositional system was significantly controlled by sub-sags. The fan delta sand body, controlled by the Eastern fault ramp, the braided river delta sand body controlled by the Western and Southern gentle slopes and the gullies, and especially the large braided river delta sand body in the northern sag controlled by the western gentle slope, are important exploration targets for oil and gas.