Abstract: There are abundant organic hydrocarbon gas and inorganic CO₂ gas resources in Dehui fault depression of southern Songliao basin. Based on the actual homogenization temperature measurement results of fluid inclusion in organic hydrocarbon gas and inorganic CO₂ gas reservoirs and in consideration of analysis of the history of tectonic evolution at the same time, there exist two periods of hydrocarbon gas accumulation at the end of Quantou formation (103×106 a)and Nenjiang formation (83×106 ~76×106 a). The formation time of CO₂ gas reservoir is controversial (98×106 a or 10×106 a). The accumulation patterns of hydrocarbon gas and inorganic CO₂ gas are significantly different. The former is slow and continuous, the latter is instantaneous and accompanied with the occurrence of mantlederived tectonic movement, and is closely related to the tectonic events. It is concluded that the inorganic CO₂ gas reservoir is accumulated later than the Yingcheng hydrocarbon gas reservoir.

Key words: Songliao basin, Dehui fault depression, Gas reservoir, CO₂ gas reservoir, Accumulation time, Accumulation sequence