Differential evolution of Bodong low uplift in Bohai Sea area and its control over oil and gas accumulation

Based on the drilling and 3D seismic data collected from the Bodong low uplift and its surrounding areas, we studied in this paper the forming process of Bodong low uplift by means of fault systems, structural styles, fault activities and balanced profiles, and its control over hydrocarbon accumulation was also discussed. Three fault systems are found well developed in the area, namely, the Paleocene-Eocene fault system, the Oligocene fault system and the Neogene fault system. The Bodong low uplift is high in the north and low in the south in an overview. The north high started rising up in early Paleogene and continued through the whole period of Dongying Formation, and as the result a single fault tilting barrier was formed. The south uplift was activated in the early stage of the rifting, and the uplifting range was relatively small. During the depositional period of the Dongying Formation, the Tanlu fault suffered a strong strike-slip move, which caused the formation of a double-fault horst. The boundary faults of the north uplift kept active, and the early and late episodes of the rift well overlapped. Oil and gas may migrate along faults to shallower reservoirs. In the double-fault horst of the south uplift, the two-step faults do not connect directly to the oil source, and thus an overlapping stratigraphic reservoir formed in the deep layer. It is believed that different reservoir-forming models on the north and south uplifts have certain guiding significance for future oil and gas exploration.