Discovery and Sedimentary Characteristics of the Neogene Delta in Bozhong Depression and Its Significance for Oil and Gas Exploration

The sedimentary facies of Neogene in Bohai sea area used to be considered as fluvial facies over a long time because of the limitation of the exploration degree. Therefore, the risks of the seal rock in the Neogene exploration were believed to be great. The standpoint has restrained the Neogene exploration in Bohai sea area. With the increasing of the exploration degree, it is recognized that Bozhong depression of Bohai sea area is one of the main catchment area for Bohai bay basin in Neogene. The lacustrine and deltaic depositional systems were discovered in Neogene in Bozhong depression in the recent years. This paper focuses on elaborating the evidences of the existence of the lacustrine and deltaic depositional systems and the characteristic of the delta depositional system(including normal lacustrine delta and braided delta).The discovery of lacustrine and deltaic depositional systems in Bozhong depression have a very important significance in the oil and gas exploration. The development area of the deltaic systems will be the major field of the exploration in Bohai sea area in the future.