Determination of oil/gas entrapment stage and time in Fuyang Reservoir of Songliao Basin

The K-Ar dating of the authigenic illite in clay minerals suggested that there had been three stages of hydrocarbon injections in the Fuyang Reservoir,Songliao Basin,and the K-Ar ages of the three stages were 70.75～72.32 Ma(in the end of K_1n),40.5～51.3 Ma(E_1~1)and 34.7～37.5 Ma(E_1~2)respectively.Therefore, the relationship between the timing of oil entrapment and the tectonic upwellings could be revealed:firstly, the Fuyang Reservoir was rapidly formed at the end of early tectonic upwelling;secondly,due to the later continuous tectonic movement,the mudstone of the Qingshangkou Formation was fissured under the high upper-pressure,and the second stage oil/gas reservoir was formed:thirdly,the last stage oil injection finished at the end of late tectonic upwelling during 34.7～37.5 Ma.