Hydrocarbon Generation and Expulsion Histories of the Upper Permian Longtan Formation in the Eastern Sichuan Basin, Southwest China

The Upper Permian Longtan Formation is the main sourcerock ofthe Lower Triassic Jialingjiang Formation in the Eastern Sichuan Basin,Southwest China. However, studies of its maturity evolution and oilgeneration and expulsion histories are lacking, which are not conduciveto the accumulation dynamics of the Jialingjiang Formation in theEastern Sichuan Basin. Based on the study of tectono-thermal historyand geochemical parameter data of the source rock, this paper usesbasin modeling technology to simulate the maturity evolution and hydrocarbongeneration and expulsion histories of the Upper Permian Longtan Formationin the Eastern Sichuan Basin. The results show that the Longtan Formationsource rock in the Eastern Sichuan Basin entered the oil generationthreshold at the middle stage of the Early Jurassic and reached thehigh-maturity stage in the north and central regions at the late stageof the Early Jurassic, and the maturity did not increase after thelate stage of the Middle Jurassic. The source rock had the characteristicof "one-stage oil generation and one-stage oil expulsion";the corresponding period of high oil expulsion was 182-174Ma (the late stage of the Early Jurassic), which was later than theformation time of the trap of the Jialingjiang Formation, possiblyproviding oil sources for the paleo-oil reservoirs of the JialingjiangFormation. The results are of great significance to the gas accumulationprocess and exploration decision-making in the Eastern Sichuan Basin.