Reservoir-Forming Periods and Accumulation Process of Chaluhe Fault Depression of Yitong Basin

It is very significant to probe the complex charging history in Chaluhe depression of Yitong basin.1D numeric modelling of hydrocarbon generation and expulsion history of source rocks in 4 wells confirms that the major source rocks had entered their threshold of maturity at the Middle-Late Eocene and reached the peak generation stage at the Early-Middle Oligocene.For this study, 145 fluid inclusion samples from 19 wells have been employed to systematically obtain information on fluorescent colors of hydrocarbon inclusions, homogenization temperatures of oil inclusions and their coeval aqueous inclusions.The results indicate three events of oil charging for the Paleocene reservoirs.By integrating with the burial historical curves, the oil charging events have been reconstructed at 38.1-27 Ma, 19.5-10 Ma and 1-0 Ma respectively.When combining the known information on hydrocarbon charging history and structural evolution, two intermittent periods of hydrocarbon migration and accumulation have been revealed, which were at 27-19.6 Ma and 10-2 Ma, respectively, corresponding to two structural uplift stages.In other words, tectonic uplift events occurring at the Late Palaeogene and the Early Neogene stopped the hydrocarbon supplies or destroyed the migrated and accumulated hydrocarbon so that hydrocarbon inclusions can not be probed at the two stages.Therefore, the Late Eocene to Middle Oligocene, Early-Middle Miocene and the Quaternary are the three important reservoir-forming periods in Chaluhe fault depression.