A New Understanding on the Sedimentary Model for the P12 of Pinghu Formation in Pinghu Oil and Gas Field, East China Sea

The sedimentary type of the lower Pinghu Formation (P12) has been a controversial issue and not formed a unifed understanding yet. The restore of paleo-salinity by trace element B shows that the sedimentation of P12 was strongly affected by the transgression and taken place in a strongly salinized water environment. The core observation indicates the sedimentation of lower Pinghu Formation was influenced bymultiple hydrodynamic forces such as tide, river etc. as demonstrated by the presence of abundant rhythmic beddings, bioturbations, and two-way flow channel sediments in the interval. P12 of Pinghu Formation belongs to tide-dominated estuarine in origin and can be proved by the conglomerate-bearing quartz sandstones of UFR sand flat in Well D. In addition, the seismic amplitude maps also reveal the sedimentary characteristics in the different part of tide-dominated estuary facies sequence i.e. incised valley fluvial deposits of the lowstand period at the lower part, tidal sand bar sedimentsof transgression period at the middle part and tidal flat deposits of highstand period at the upper part. Accordingly, a sedimentary evolution model of the tide-dominated estuary sedimentation recorded in the lower Pinghu Formation (P12) is summarized.