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Lowstand Fans Formation and Their Hydrocarbon Accumulation Since Middle Miocene, Yinggehai and Qiongdongnan Basins


Jiang, Tao, Xinong Xie, Jianye Ren, China University of Geosciences, Wuhan, China


This study distinguishes fourth sequence from seismic data and reveals that the strati­graphical patterns of the Yinggehai continental margin are mainly characterized by the progradational slope prisms. In the Qiongdongnan area, however, the slope margins show a stacking pattern in vertical or a little shift seaward, in which a very wide shelf forms, a plen­tiful of gravitational slipping faults and slump deposits develop. This kind of stratigraphical architecture indicates that sediments at lower and base of slope position are controlled by gravitational flow processes. The evolution of shelf-slope offers the background of lowstand fans formation. The study to stratigraphy and subsidence shows that the factors impacting lowstand fans formation involve tectonic, sea-level changes, sediment supply and climate. The dynamic modeling is executed by Computer Fluid Dynamic software°ªFLUENT. The sim­ulation can distinctly display the forming process of lowstand fans including slope fan, basin floor fan and lowstand wedge and reveal the ingredients deciding the type and scale of low­stand fans. Furthermore, because the fluid velocity of deepwater turbidite has less change scope and can be looked as a consant, on the condition of given slope which is decided by local geology setting, grain size controls the type and characteristics of lowstand fans. The result may be used to estimate hydrocarbon reservoir based on the characteristics of low­stand fans, which can be gained by seismic data, and correlative wells. Finally, the models of hydrocarbon accumulation in lowstand fans are summarized since Middle Miocene in the Yinggehai and Qiongdongnan basins.