| It is very important to systemically study the sedimentary mechanism and distribution of source rock of the Oligocene Lingshui Formation in Lingshui Sag for the successive petroleum exploration in deep water area of Qiongdongnan Basin. Based on 2D seismic data and drilling data, the Lingshui Formation is subdivided into three third-order sequences. Within the sequence stratigraphic framework, six types of seismic facies such as mound, wedge, oblique, sheet, filling, and wave are identified. According to the theory of seismic sedimentology, five types of sedimentary facies such as coastal plain, shallow sea, bathyal sea, submarine fan, and fan delta are identified. The sedimentary characteristic of each sequence is analyzed, especially of the coastal plain and shallow sea affected by the separated paleo-uplifts. By integrated analysis of geochemical data and sedimentary facies, the source rock development model of Lingshui Formation is setup in Lingshui Sag. The coal-bearing rocks mainly developed in the coastal plain along Lingnan low uplift and Songnan low uplift to the east of sag, with sufficient input of terrestrial organic matter. The marine source rocks with terrestrial input mainly developed in the shallow sea and bathyal facies along those fan delta systems, in which terrestrial organisms is predominant and aquatic organisms is minor. |
