The petroleum system in the south of Songliao basin.

Petroleum system division is the precondation and base of petroleum system stu dy. In the light of conception of petroleum system and based on the principle th at if a petroleum basin has several sets of mature source rocks, there exist sev eral petroleum systems. The middle upper strata of southern Songliao basin are divided into two petroleum systems and one composite petroleum system, according to the development and distribution of effective source rock, oil and gas distr ibution and the hydrocarbon source c orrelation for the south of Songliao basin, and combined with the structural cha racteristic and reservoir distribution of the basin. From the analysis of three petroleum systems′ characteristics in detail it can draw conclusions that: (1) F or K 1q n-P G F Y petroleum system, source rock quality is good, evolution degree is high. So this is a mature and high mature system. (2) For K 1n 1 2 -H petroleum system, evolution degree is low. So this is a low mature and h igh mature petroleum system. (3) K 1q n K 1n 1 2 -S petroleum syste m is a mature composite system.