Thermal simulation of hydrocarbon expulsion from Eogene source rock in Damintun Depression were mnde with high temperature-pressure semi-closed experimental system.The results show that the factor controlling hydrocarbon expulsion amounts is organic matter abundance of the source rock

but the factor controlling expulsion efficiency is the type of organic matter. Higher expulsion amount does not always mesn higher expulsion effciency. The content of alkanes and NSO compounds in crude oil is remarkably affected by hydrocarbon expulsion

while that of aromatics is only slightly affected. Hydrocarbon expulsion models of the souree rocks in the depression are characterized by no abrupt peak of petroleum expulsion.