Distribution of sedimentary system multi-controlled by palaeo-geomorphology, water system and break during the deposition of Pinghu Formation, Baochu slope belt, Xihu Sag, East China Sea Shelf Basin

Abstract

The Xihu Sag has huge exploration potential and is the main target for oil and gas exploration in the East China Sea Shelf Basin. At present, it has been known that the Xihu Sag has a transitional facies with sedimentary system mainly composed of tidal flat deposits, and the provenance of which is dominated by western and northern uplift area. However, the transport process of sands from source area to deposit area, namely "source-channel-sink" system, has not been well studied. In this study, we take the Pinghu Formation of Baochu slope belt in the Xihu Sag as research object, and use borehole and seismic data to preform high-precision restoration of palaeo-geomorphology. Moreover, on the basis of palaeo-geomorphology restoration, we make qualitative and quantitative analyses of palaeo-water-system and palaeo-break. Results show that the location of sink zone is controlled by palaeo-geomorphology, the distribution of sand transporting channel is controlled by palaeo-water-system, and the development of sedimentary facies is controlled by palaeo-break. Through comprehensive analysis, we suppose that the combination of "palaeo-geomorphology, palaeo-water-system and palaeo-break" restricts the process of sand body deposition from provenance to convergence area through river transportation, and controls the distribution of the sedimentary system of Baochu slope belt.

Keywords

• palaeo-geomorphology
• source-channel-sink
• sedimentary system
• pinghu formation
• eocene
• xihu sag
• east china sea shelf basin