LATE PALEOCENE SEA-LEVEL FLUCTUATIONS AND PREDICTION OF FAVOURABLE RESERVOIRS IN LISHUI SAG,EAST CHINA SEA BASIN

According to the data of lithology, palaeontology, heavy minerals, logging and seismic in 9 wells, the Late Paleocene sea_level fluctuations are analysed and the favorable reservoirs are predicted in Lishui sag. During Late Paleocene there were two greater transgressions in the sag. The first one occurred in Late Lingfeng, during which Lingfeng salient belt in the central Lishui sag was still not inundated and became a local provenance. In the meantime, there were fan delta systems along the margin of the sag, and neritic deposition systems with gravity flow in the central sag. The second transgression, greater than the first, may occur in Middle Mingyuefeng, during which the sag margin was shallow sea and Lingfeng salient was inundated and became a carbonate platform. Meanwhile, multiple gravity slumps took place on the steep slope of the sag, turbidity fans formed in its deepwater area that is the center of subsidence and deposition in the western sub_sag. In Lishui sag, the discovered oil_gas bearing reservoirs are mainly deepwater turbidity fan sandstones under the maximal flooding surfaces of the two transgressions. But similar sandstones developed more widely in the western sub_sag, of which the best ones are in Mingyuefeng Formation in the central sag adjacent to the west side of Lingfeng salient belt.