Songliao Basin is a superposed basin composed of fault-subsidence and depression. The pool forming system of the fault-subsidence was controlled by faulting and subsiding intensity. The source rocks of the basin are mainly type-Ⅲ and type-Ⅱ

B

of high thermal evolution. Hydrocarbon generation took place quite early and most of the hydrocarbon is natural gas. Hydrocarbon migrated vertically through faults and fractures associating with lateral migration along T

3

T

4

interfaces. Traps such as contemporaneous

early stage structural and multistage composite traps are favourable for trapping oil and gas. Since the traps are small

source rock are dispersive and posttectonic reworking was intensive

the pool-forming efficiency is quite low. As for the depressed basin

its source rock distribution is stable and extensive

the kerogens are primarily type-Ⅰand type-Ⅱ

A

and on the whole

the evolution degree of organic matter is lower. Hydrocarbon

mainly oil associated with gas

generated late in the depressed basin. Oil and gas in the basin migrated laterally along T

1

T

2

interfaces and reservoirs. Verious kinds of traps superposed on paleo-uplifts and paleo-slopes are more favourable to form oil and gas pools.