Key moments for hydrocarbon accumulation in Shaximiao Formation on the eastern slope of West Sichuan Depression, Sichuan Basin

The West Sichuan Depression in the Sichuan Basin is a foreland basin formed under the compressional thrusting of the Longmen Mountain. 3D seismic was obtained on five exploration blocks on the eastern slope of the central depression, including Hexingchang-Gaomiaozi, Fenggu, Yongtai, Zhongjiang-Huilong and Zhixinchang-Shiquanchang, covering three tectonic belts. The hydrocarbon evolution history of source rocks was studied, and 22 fluid inclusion samples from 6 wells were analyzed using fluorescence, homogenization temperature and salinity measurements. Source rocks in the fifth member of the Upper Triassic Xujiahe Formation entered the hydrocarbon generation threshold at 151-145 Ma, and reached a peak at 130 Ma. Three stages of fluid activities related to hydrocarbon accumulation took place in sandstone reservoirs in the Jurassic Shaximiao Formation at 141-128 Ma (J₃-K₁), 105-88 Ma (K₁-K₂) and 83-68 Ma (K₂), respectively. The peak of hydrocarbon generation of source rocks at 130-68 Ma (K₁-K₂) is the key moment for hydrocarbon accumulation.