Based on the analyses of 376 samples of fluid inclusions from the middle Es

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in the Dongying sag

hydrocarbon charging in the study area was divided into three different stages with exact time.The evolution of paleo-formation pressure during these three charging stages was obtained through PVT thermodynamic modeling of the fluid inclusions.The results in combination with the plane and sectional views of current pressure distribution reveal that the hydrocarbon reservoirs in Es

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belong to the same pressure system.The evolution of paleo-fluid potential fields in Es

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during these three stages were reconstructed with the parameters obtained from fluid inclusion analysis and their distribution features were analyzed.The favorable areas for hydrocarbon accumulation during these three periods of hydrocarbon charging were discussed.It is believed that the reservoir distribution in the Dongying sag was closely related to the evolution of paleo-fluid potential

and the thresholds of paleo-fluid potential controlling hydrocarbon accumulation in these three charging periods were 7 kJ/kg

10.5 kJ/kg and 22 kJ/kg respectively.The northern slope of the Lijin subsag and the southern slope of the Niuzhuang subsag were the favorable areas for hydrocarbon accumulation during the first period of hydrocarbon charging;the surrounding areas of the Lijin and the Niuzhuang subsags(high oil potential centrers) were the favorable areas during the second period of hydrocarbon charging;while the surrounding areas of the Minfeng and the Boxing subsags were the favorable areas during the third period of hydrocarbon charging.