Analysis on the origin of lithological sand in the Lower Member of Paleocene Mingyuefeng Formation in West Lishui Sag, East China Sea

In the case of lack of well data, to finely characterize a lithologic trap by means of seismic sedimentology becomes an urgent task. Focusing on the seismic facies characteristics of the Lower Member of the Mingyuefeng Formation , the main producing reservoirs in the Lishui Sag in the continental shelf of East China Sea was explored, and the formation and evolution of sand unit of the member were analyzed in combination of attraction of horizon attributes, reservoir inversion, and 3D lithologic carving on the basis of sequence stratigraphic division. The results show that the Lower Member of Mingyuefeng Formation could be subdivided into four system tracts, i.e., the falling-stage system tract, lowstand system tract, and transgressive and highstand systems tracts. In the falling-stage and lowstand systems tracts, two incised channels were developed above the fault slope-break zone and these channels transported sand to the edge of the shelf and formed the ancient delta frontal deposits. In addition, in the falling-stage system tract, a thin-layer of turbidite formed in the front edge of the delta with plentiful sediment supply. Both the transgressive and highstand systems tracts have developed beach-bar barrier island deposits that had been subjected to the wave action and they are mainly distributed in the structural slope-break zone due to poor sediment supply. This study could effectively guide the prediction of lithologic trap in the Mingyuefeng Formation in the study area and provide decision-making basis for further exploration deployment.