Source and migration direction of oil and gas in Kongqueting area, Xihu Sag, East China Sea Shelf Basin

Kongqueting is a key exploration area in the Xihu sag of the East China Sea Shelf Basin. The ambiguity in source and migration direction of oil and gas has brought difficulties in efficient oil and gas exploration. This time, the source of oil and gas is jointly determined by the study of oil and gas characteristics and distribution patterns, the correlation of the biomarkers between source rocks and crude oil, and the calculation of the maturity of natural gas. In combination with the migration effect of oil and gas, the migration direction of crude oil and natural gas are discussed. The results suggest that the crude oil in Kongqueting area mainly comes from the source rocks of the Lower Pinghu Formation and Baoshi Formation, with a little from the Middle Pinghu Formation. Crude oil migrates mainly from the secondary depressions to the higher part of the slope for oil accumulation. In terms of natural gas, there are dual sources, one local source and one the source from the Western Subsag. The natural gas generated from the Western Subsag migrates from low zone to high zone along the slope, and mixed with natural gas generated by local source rock of the slope zone on the way, suggesting a pattern of vertical migration. Therefore, the low part of the slope is a potential area for natural gas exploration.