Sedimentary Facies and Depositional Mode of Deep Reservoirs of Baoshi Formation in Xihu Depression

Xihu Depression was one of the largest depressions in offshore areas of China,and also a key natural gas exploration area.Currently,the researches were focused on Eocene Pinghu Formation and Oligocene Huagang Formation.However,the research on deep reservoirs of Eocene Baoshi Formation was extremely weak.Based on single-well core fine observation,comprehensive application of paleontology,core,well logging and seismic data,the sedimentary facies type,sedimentary characteristics and distribution of deep reservoirs of Baoshi Formation in Xihu Depression were analyzed.The results show that Baoshi Formation mainly develops fluvial facies,delta facies,lacustrine facies,and fan-delta facies.Among them,the river and delta deposits are developed in the western gentle slope belt of Xihu Depression,and fan-delta sediments are developed in the eastern steep slope zone,lacustrine facies is widely distributed,the distributing area of semi-deep lacustrine is small,they are manly distributed in the center of the depression.On the basis stated above,the depositional model of Baoshi Formation in Xihu Depression is established.