Structural Evolution And Resource Effect Of The Deepwater Area, The Northern Margin Of The South China Sea

There were abundant resources contained in the deepwater area of the northern margin of the South China Sea (NMSCS). The study on deepwater area just begins in China which has already been the scientific hotspot. Structural evolution of the hydrocarbon-bearing basin is one of the most important basic researches about the hydrocarbon exploration, therefore, it is important for the theory and reality to study the structural evolution and resource effect of the deepwater area of NMSCS.Based on the drilling and seismic data and regional geological document, this study was carried out mainly on the architecture and structural evolution characteristics of the deepwater area of the Pearl River Mouth Basin (PRMB). Innovative results had been achieved as follows. 1) The architecture of study area and the development characteristics of each structural unit were firstly and systematically analyzed with the half-graben analysis method and five favorable hydrocarbon migration zones were pointed on the basis of basin structure study. 2) Calibrated according to the latest data, the more reliable tectonic subsidence curve of the study area was calculated with the back-stripping method. The boundary of the rift and post-rift stages was redefined. The study indicated that the rifting activity still continued after the seafloor spreading of SCS at 32 Ma and culminated at 23 Ma when the large-scale post-rift thermal subsidence started. The formation mechanisms of the rifting prolongation were explained. 3) The stretching factor calculation equation with the discontinuous stretching model was deducted and crust and mantle stretching factor of the study area were calculated respectively. The results demonstrated the preferential mantle lithospheric extension under the deepwater area of PRMB relative to the crust. The structural development history of the study area was rebuilt firstly based on the balance cross-section method, and the stretching ratio and deposition rate were calculated for each structural period. The study area was proved to be stretched continuously during Cenozoic on the whole and the stretching factor was between 1.1 and 1.24. 4) The geological features of the gas hydrate drilling zone were delineated accurately and the conceptual model for the gas hydrate accumulation was postulated; A set of fluid potential calculation method just based on the seismic stack velocity was established, which provided a new clue to study the gas hydrate accumulation law.