Abstract: Anyue gas field,resulted from the in-situ pyrolysis of paleo-oil reservoirs in the Neoproterozoic-Lower Paleozoic sequences,is one of the largest old and deep gas pools in China.Since the paleo oil-pyrolysis gas pools are high in degree of evolution and very old,and there is in lack of geochemical evidences,the accumulation and evolution,especially the timing of accumulation,remains a controversial issue in study.Starting from the newly-measured terrestrial heat flow history and threshold depth of hydrocarbon generation from source rocks in similar areas,we apply geological analogy method,instead of microthermometry of fluid inclusions,to the analysis of paleo-oil reservoir evolution:reconstructing the burial-geothermal history of key wells,and then determining the timing of hydrocarbon generation in the Qiongzhusi Formation source beds in Deyang-Ziyang rift and of paleo-oil reservoirs' formation and destruction.The results of geochemical experiments and relevant geological analyses indicate that hydrocarbon generation in the Qiongzhusi Formation source rock and paleo-oil reservoir formation occurred around 275-263 Ma,corresponding to the late Early Permian-Late Permian.The oil pyrolysis occurred since the early Triassic with deep burial,and the paleo-oil reservoirs were entirely transformed to a pyrolysis gas pools during the late Middle Jurassic-early Early Cretaceous.

Key words: burial history, hydrocarbon accumulation time, pyrolysis gas pool, paleo-oil reservoir, Anyue gas field, Chuanzhong Uplift, Sichuan Basin