Structure Characteristics and Favorable Hydrocarbon Exploration Zone of Bodong Depression in Bohai Sea Area

Through comprehensive study on the structure and evolution history of Bodong depression, it has been clear that Bodong depression is characterized by zonation between east and west, and division from north to south. In the plane, Bodong depression is divided into east and west zones, being NNE-direction half graben in the west, distributed in series connection. In the east of Bodong depression, the half grabens are distributed as parallel connection in NE-direction. In the section, the structure of Bodong depression changed from simple half graben in the north of depression into complicated half graben in the middle and south of depression. In this paper, it is illustrated that the structure evolution of depression controlled the hydrocarbon generation potential of depression. Four types of hydrocarbon accumulation models of Bodong depression have been established, which are draped anticline reservoirs on the relief, buried hill reservoirs, hydrocarbon generation in the lower source rock and accumulation in upper reservoirs in the center strike-slip fault zone, and structure-lithology reservoirs in slope zone. It is predicated that there are four favorable exploration belts in Bodong depression, including Bodong low uplift, the center strike-slip fault zone, the slope zone of the second low-lying in the west and the slope zone of the first low-lying in the east, of which the southern part of Bodong low uplift and the slope zone of the second low-lying in the west are the most favorable exploration area, which are located near the main hydrocarbon generation center.