Continental margin sediment dispersal under geomorphic control in Xihu Depression, East China Sea Shelf Basin

Abstract

Abstract The system of sediment dispersal of the continental margin has always been a hot and difficult study topic because of its diversity and complexity, and its dispersal processes and influence on the exploration of reservoirs have puzzled most researchers. Based on the comprehensive analysis of the seismic geomorphology and fault combinations, the seismic facies, and the sum of positive amplitude attributes, we describe the characteristics of the sediment dispersal pathways, and discussing its influence on the exploration of sand-rich reservoirs of the middle part of Pinghu Formation in the Pingbei Slope Belt of Xihu Depression (East China Sea Shelf Basin). The results showed that three modes of sediment dispersal system were established by comparing the geological background and the sediment dispersal pathways of the Pingbei Slope Belt. 1) The “straight mode” developed in the Tuanjieting area is characterized by a group of effective pathways directly connected to the channels developed in the land, then go through the marginal fault and ended in the gentle slope. The sand-rich lobes consisted of rapid accumulation of sediments are the most important target for the exploration of reservoirs, the scale of reservoirs could be easily recorded by the measurement of the area and the thickness of the chaotic reflectors developed in this area. 2) The “restricted mode” developed in the Baoyunting area is largely limited by the depression bounded by the uplift, the sediment dispersal pathways are genetically related to the scale and shape of this depression. The depocenters could be a guidance for the development of sand-rich reservoirs, large-scale sand-rich reservoirs could be formed as long as the depression is large enough. 3) The “migration mode” developed in the Kongqueting area is controlled by the slope and normal fault combinations, the long-distance and short-distance sediment dispersal pathways are developed. The area that developed the long-distance sand-rich sediments in the background of relatively low fault growth ratio shall be the most important target for reservoir exploration and easy to form large-scale sand-rich reservoirs.