Abstract: Several slope-breaks are developed on the western slope of the west subsag in Lishui depression, which control the development of distal underwater fans in the lower part of the Paleocene Mingyuefeng Formation. Drilling reveals that the underwater fans are characterized by large sedimentary thickness, good physical properties,and active hydrocarbon-bearing. The description of reservoir characteristics and prediction of distribution range are of great significance to the exploration of lithologic reservoirs in this area. Through analysis of the paleo-geomorphology in the early stage of Mingyuefeng Formation, the effects of slope-breaks on fan development are summarized. Isolated and compound channels are developed in the upthrow block; while the main fan bodies are developed in the downthrow wall of slope break faults. The microfacies of the fan channel is the dominant facies. The main lithology is gray fine sandstone. There are sedimentary structures reflecting collapse, such as water escaping structure and flaming structure. The logging facies are characterized by low gamma and high spontaneous potential anomalies, and the seismic facies are characterized by strong amplitude, low frequency and intermittent reflection. At the same time, the distribution range of three fan stages in this area is identified by using seismic sedimentology technology. From early to late stage, the fans have gradually migrated from north to south, which points out the direction for future exploration in this area.

Key words: far-shore underwater fan, Lishui sag, Mingyuefeng Formation, seismic sedimentology