Abstract:

The upper He-3 sequence of the Biyang Sag is used in this paper as an example to illustrate the workflow of Seismic Sedimentology. On the basis of subtle sequence framework, a stratal slice cube was made which displayed the distribution of sedimentary microfacies, and the analysis of the cube enabled the interpretation of the evolutionary history. Through the comprehensive analysis of core, lithology and well-logging, the sandbodies of the typical slices were interpreted elaborately, and some conclusions were drawn as follows. There exist three denuded areas in the north-east, south-east and south-west, respectively, which provided the terrigenous clasts to the deep depression of the Biyang Sag, and where developed correspondingly the three sedimentary formations, i.e., the Houzhuang braided delta in the north-east, the Lishuwa nearshore subaqueous fan in the south-east and the Yangqiao nearshore subaqueous fan in the south-west. In the deep depression, slump turbidite fans were developed. The progradational configuration of braided delta front always associated with the lenticular reflection in strike direction, which showed the process of the sand bodies sliding from delta front into semideep to deep lacus and being wrapped by mudstone. Finally, the paper predicts the distribution of sedimentary facies and provides the reliable evidence of exploration of subtle traps such as slump turbidite fans. The result was verified by Well Anshen 1.

Key words: stratal slice, seismic sedimentology, slump turbidite fan, He-3 Formation, Biyang Sag